diff --git a/lib/enu/diagnosticMessages.generated.json.lcg b/lib/enu/diagnosticMessages.generated.json.lcg
index 13173d17d73..a3f7dd8da25 100644
--- a/lib/enu/diagnosticMessages.generated.json.lcg
+++ b/lib/enu/diagnosticMessages.generated.json.lcg
@@ -5421,9 +5421,9 @@
               </Str>
               <Disp Icon="Str" />
             </Item>
-            <Item ItemId=";The_type_of_a_function_declaration_must_be_callable_8030" ItemType="0" PsrId="306" Leaf="true">
+            <Item ItemId=";The_type_of_a_function_declaration_must_match_the_function_s_signature_8030" ItemType="0" PsrId="306" Leaf="true">
               <Str Cat="Text">
-                <Val><![CDATA[The type of a function declaration must be callable.]]></Val>
+                <Val><![CDATA[The type of a function declaration must match the function's signature.]]></Val>
               </Str>
               <Disp Icon="Str" />
             </Item>
diff --git a/lib/lib.es5.d.ts b/lib/lib.es5.d.ts
index ac73e23d9f6..840fd682789 100644
--- a/lib/lib.es5.d.ts
+++ b/lib/lib.es5.d.ts
@@ -1145,15 +1145,15 @@ interface Array<T> {
       * Returns a string representation of an array. The elements are converted to string using their toLocalString methods.
       */
     toLocaleString(): string;
+    /**
+      * Removes the last element from an array and returns it.
+      */
+    pop(): T | undefined;
     /**
       * Appends new elements to an array, and returns the new length of the array.
       * @param items New elements of the Array.
       */
     push(...items: T[]): number;
-    /**
-      * Removes the last element from an array and returns it.
-      */
-    pop(): T | undefined;
     /**
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.
diff --git a/lib/tsc.js b/lib/tsc.js
index 2cc079c7b64..c068dcddbf8 100644
--- a/lib/tsc.js
+++ b/lib/tsc.js
@@ -2241,18 +2241,16 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 if (platform === "win32" || platform === "win64") {
                     return false;
@@ -3680,7 +3678,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -24034,8 +24032,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -27460,13 +27458,7 @@ var ts;
                         return getReturnTypeOfSignature(getterSignature);
                     }
                 }
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -42189,11 +42181,11 @@ var ts;
                 if (functionFlags & 1 && ts.nodeIsPresent(body)) {
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -42257,7 +42249,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95;
@@ -42276,14 +42268,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8)) {
-                                addDiagnostic(0, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8)) {
-                                    addDiagnostic(0, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -42302,7 +42294,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -42353,7 +42345,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -42370,7 +42362,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0, unuseds.length === 1
+                    addDiagnostic(importDecl, 0, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -42389,7 +42381,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -42397,21 +42389,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0, declarations.length === 1
+                    addDiagnostic(declarationList, 0, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -44589,8 +44581,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -50318,6 +50310,9 @@ var ts;
                 case 203:
                     node = node.condition;
                     continue;
+                case 191:
+                    node = node.tag;
+                    continue;
                 case 189:
                     if (stopAtCallExpressions) {
                         return node;
@@ -66567,7 +66562,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -67013,6 +67008,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json"]) : undefined;
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
         var _referencesArrayLiteralSyntax;
@@ -67978,7 +67974,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -70331,16 +70327,15 @@ var ts;
             onUnRecoverableConfigFileDiagnostic: host.onUnRecoverableConfigFileDiagnostic
         };
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -70992,6 +70987,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }
diff --git a/lib/tsserver.js b/lib/tsserver.js
index 37d4c81272d..6ae31807397 100644
--- a/lib/tsserver.js
+++ b/lib/tsserver.js
@@ -3923,7 +3923,7 @@ var ts;
         return parseInt(version.substring(1, dot));
     }
     ts.getNodeMajorVersion = getNodeMajorVersion;
-    // TODO: this is used as if it's certainly defined in many places.
+    // TODO: GH#18217 this is used as if it's certainly defined in many places.
     ts.sys = (function () {
         // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
         // byte order mark from the specified encoding. Using any other byte order mark does
@@ -4032,18 +4032,17 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                // See https://github.com/Microsoft/TypeScript/issues/25652
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 // win32\win64 are case insensitive platforms
                 if (platform === "win32" || platform === "win64") {
@@ -5545,7 +5544,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -29475,8 +29474,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -33448,13 +33447,7 @@ var ts;
                     }
                 }
                 // Use contextual parameter type if one is available
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -50798,12 +50791,12 @@ var ts;
                     // yielded values. The only way to trigger these errors is to try checking its return type.
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0 /* Call */).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -50870,7 +50863,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0 /* Local */, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95 /* _ */;
@@ -50890,14 +50883,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8 /* Private */)) {
-                                addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155 /* Constructor */:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8 /* Private */)) {
-                                    addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -50919,7 +50912,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -50974,7 +50967,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -50991,7 +50984,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 /* NamespaceImport */ ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0 /* Local */, unuseds.length === 1
+                    addDiagnostic(importDecl, 0 /* Local */, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -51010,7 +51003,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -51018,21 +51011,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0 /* Local */, declarations.length === 1
+                    addDiagnostic(declarationList, 0 /* Local */, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 /* VariableStatement */ ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -53610,8 +53603,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -60029,6 +60022,9 @@ var ts;
                 case 203 /* ConditionalExpression */:
                     node = node.condition;
                     continue;
+                case 191 /* TaggedTemplateExpression */:
+                    node = node.tag;
+                    continue;
                 case 189 /* CallExpression */:
                     if (stopAtCallExpressions) {
                         return node;
@@ -82066,7 +82062,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -82558,6 +82554,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json" /* Json */]) : undefined;
         // Map storing if there is emit blocking diagnostics for given input
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
@@ -83706,7 +83703,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -86476,16 +86473,15 @@ var ts;
         };
         // From tsc we want to get already parsed result and hence check for rootFileNames
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -87200,6 +87196,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }
@@ -96219,7 +96216,7 @@ var ts;
             "borrows",
             "callback",
             "class",
-            "classDesc",
+            "classdesc",
             "constant",
             "constructor",
             "constructs",
@@ -96236,16 +96233,16 @@ var ts;
             "external",
             "field",
             "file",
-            "fileOverview",
+            "fileoverview",
             "fires",
             "function",
             "generator",
             "global",
-            "hideConstructor",
+            "hideconstructor",
             "host",
             "ignore",
             "implements",
-            "inheritDoc",
+            "inheritdoc",
             "inner",
             "instance",
             "interface",
@@ -96254,7 +96251,7 @@ var ts;
             "license",
             "listens",
             "member",
-            "memberOf",
+            "memberof",
             "method",
             "mixes",
             "module",
@@ -96846,7 +96843,7 @@ var ts;
         /** Call after calling `startNode` and adding children to it. */
         function endNode() {
             if (parent.children) {
-                mergeChildren(parent.children);
+                mergeChildren(parent.children, parent);
                 sortChildren(parent.children);
             }
             parent = parentsStack.pop();
@@ -97002,7 +96999,7 @@ var ts;
             }
         }
         /** Merge declarations of the same kind. */
-        function mergeChildren(children) {
+        function mergeChildren(children, node) {
             var nameToItems = ts.createMap();
             ts.filterMutate(children, function (child) {
                 var declName = ts.getNameOfDeclaration(child.node);
@@ -97019,7 +97016,7 @@ var ts;
                 if (itemsWithSameName instanceof Array) {
                     for (var _i = 0, itemsWithSameName_1 = itemsWithSameName; _i < itemsWithSameName_1.length; _i++) {
                         var itemWithSameName = itemsWithSameName_1[_i];
-                        if (tryMerge(itemWithSameName, child)) {
+                        if (tryMerge(itemWithSameName, child, node)) {
                             return false;
                         }
                     }
@@ -97028,7 +97025,7 @@ var ts;
                 }
                 else {
                     var itemWithSameName = itemsWithSameName;
-                    if (tryMerge(itemWithSameName, child)) {
+                    if (tryMerge(itemWithSameName, child, node)) {
                         return false;
                     }
                     nameToItems.set(name, [itemWithSameName, child]);
@@ -97036,16 +97033,16 @@ var ts;
                 }
             });
         }
-        function tryMerge(a, b) {
-            if (shouldReallyMerge(a.node, b.node)) {
+        function tryMerge(a, b, parent) {
+            if (shouldReallyMerge(a.node, b.node, parent)) {
                 merge(a, b);
                 return true;
             }
             return false;
         }
         /** a and b have the same name, but they may not be mergeable. */
-        function shouldReallyMerge(a, b) {
-            if (a.kind !== b.kind) {
+        function shouldReallyMerge(a, b, parent) {
+            if (a.kind !== b.kind || a.parent !== b.parent && !(isOwnChild(a, parent) && isOwnChild(b, parent))) {
                 return false;
             }
             switch (a.kind) {
@@ -97060,6 +97057,12 @@ var ts;
                     return true;
             }
         }
+        // We want to merge own children like `I` in in `module A { interface I {} } module A { interface I {} }`
+        // We don't want to merge unrelated children like `m` in `const o = { a: { m() {} }, b: { m() {} } };`
+        function isOwnChild(n, parent) {
+            var par = ts.isModuleBlock(n.parent) ? n.parent.parent : n.parent;
+            return par === parent.node || ts.contains(parent.additionalNodes, par);
+        }
         // We use 1 NavNode to represent 'A.B.C', but there are multiple source nodes.
         // Only merge module nodes that have the same chain. Don't merge 'A.B.C' with 'A'!
         function areSameModule(a, b) {
@@ -97076,7 +97079,7 @@ var ts;
             }
             target.children = ts.concatenate(target.children, source.children);
             if (target.children) {
-                mergeChildren(target.children);
+                mergeChildren(target.children, target);
                 sortChildren(target.children);
             }
         }
@@ -99334,8 +99337,8 @@ var ts;
                 var name = importNameForConvertToDefaultImport(importNode);
                 if (!name)
                     continue;
-                var module = ts.getResolvedModule(sourceFile, moduleSpecifier.text);
-                var resolvedFile = module && program.getSourceFile(module.resolvedFileName);
+                var module_1 = ts.getResolvedModule(sourceFile, moduleSpecifier.text);
+                var resolvedFile = module_1 && program.getSourceFile(module_1.resolvedFileName);
                 if (resolvedFile && resolvedFile.externalModuleIndicator && ts.isExportAssignment(resolvedFile.externalModuleIndicator) && resolvedFile.externalModuleIndicator.isExportEquals) {
                     diags.push(ts.createDiagnosticForNode(name, ts.Diagnostics.Import_may_be_converted_to_a_default_import));
                 }
@@ -101973,7 +101976,6 @@ var ts;
                 // split comment in lines
                 var startLine = sourceFile.getLineAndCharacterOfPosition(commentRange.pos).line;
                 var endLine = sourceFile.getLineAndCharacterOfPosition(commentRange.end).line;
-                var parts;
                 if (startLine === endLine) {
                     if (!firstLineIsIndented) {
                         // treat as single line comment
@@ -101981,18 +101983,18 @@ var ts;
                     }
                     return;
                 }
-                else {
-                    parts = [];
-                    var startPos = commentRange.pos;
-                    for (var line = startLine; line < endLine; line++) {
-                        var endOfLine = ts.getEndLinePosition(line, sourceFile);
-                        parts.push({ pos: startPos, end: endOfLine });
-                        startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
-                    }
-                    if (indentFinalLine) {
-                        parts.push({ pos: startPos, end: commentRange.end });
-                    }
+                var parts = [];
+                var startPos = commentRange.pos;
+                for (var line = startLine; line < endLine; line++) {
+                    var endOfLine = ts.getEndLinePosition(line, sourceFile);
+                    parts.push({ pos: startPos, end: endOfLine });
+                    startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
                 }
+                if (indentFinalLine) {
+                    parts.push({ pos: startPos, end: commentRange.end });
+                }
+                if (parts.length === 0)
+                    return;
                 var startLinePos = ts.getStartPositionOfLine(startLine, sourceFile);
                 var nonWhitespaceColumnInFirstPart = formatting.SmartIndenter.findFirstNonWhitespaceCharacterAndColumn(startLinePos, parts[0].pos, sourceFile, options);
                 if (indentation === nonWhitespaceColumnInFirstPart.column) {
@@ -102532,6 +102534,9 @@ var ts;
                                 getListIfStartEndIsInListRange(node.parent.parameters, start, end);
                         }
                         case 238 /* ClassDeclaration */:
+                        case 207 /* ClassExpression */:
+                        case 239 /* InterfaceDeclaration */:
+                        case 240 /* TypeAliasDeclaration */:
                             return getListIfStartEndIsInListRange(node.parent.typeParameters, node.getStart(sourceFile), end);
                         case 190 /* NewExpression */:
                         case 189 /* CallExpression */: {
@@ -102741,17 +102746,10 @@ var ts;
             function isControlFlowEndingStatement(kind, parent) {
                 switch (kind) {
                     case 228 /* ReturnStatement */:
-                    case 232 /* ThrowStatement */: {
-                        if (parent.kind !== 216 /* Block */) {
-                            return true;
-                        }
-                        var grandParent = parent.parent;
-                        // In a function, we may want to write inner functions after this.
-                        return !(grandParent && grandParent.kind === 194 /* FunctionExpression */ || grandParent.kind === 237 /* FunctionDeclaration */);
-                    }
+                    case 232 /* ThrowStatement */:
                     case 226 /* ContinueStatement */:
                     case 227 /* BreakStatement */:
-                        return true;
+                        return parent.kind !== 216 /* Block */;
                     default:
                         return false;
                 }
@@ -106134,31 +106132,32 @@ var ts;
             var statement = ts.findAncestor(token, ts.isStatement);
             ts.Debug.assert(statement.getStart(sourceFile) === token.getStart(sourceFile));
             var container = (ts.isBlock(statement.parent) ? statement.parent : statement).parent;
-            switch (container.kind) {
-                case 220 /* IfStatement */:
-                    if (container.elseStatement) {
-                        if (ts.isBlock(statement.parent)) {
-                            changes.deleteNodeRange(sourceFile, ts.first(statement.parent.statements), ts.last(statement.parent.statements));
+            if (!ts.isBlock(statement.parent) || statement === ts.first(statement.parent.statements)) {
+                switch (container.kind) {
+                    case 220 /* IfStatement */:
+                        if (container.elseStatement) {
+                            if (ts.isBlock(statement.parent)) {
+                                break;
+                            }
+                            else {
+                                changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
+                            }
+                            return;
                         }
-                        else {
-                            changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
-                        }
-                        break;
-                    }
-                // falls through
-                case 222 /* WhileStatement */:
-                case 223 /* ForStatement */:
-                    changes.delete(sourceFile, container);
-                    break;
-                default:
-                    if (ts.isBlock(statement.parent)) {
-                        var end_2 = start + length;
-                        var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
-                        changes.deleteNodeRange(sourceFile, statement, lastStatement);
-                    }
-                    else {
-                        changes.delete(sourceFile, statement);
-                    }
+                    // falls through
+                    case 222 /* WhileStatement */:
+                    case 223 /* ForStatement */:
+                        changes.delete(sourceFile, container);
+                        return;
+                }
+            }
+            if (ts.isBlock(statement.parent)) {
+                var end_2 = start + length;
+                var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
+                changes.deleteNodeRange(sourceFile, statement, lastStatement);
+            }
+            else {
+                changes.delete(sourceFile, statement);
             }
         }
         function lastWhere(a, pred) {
@@ -109793,9 +109792,9 @@ var ts;
                 if (isTopLevelDeclarationStatement(statement) &&
                     !isExported(sourceFile, statement, useEs6Exports) &&
                     forEachTopLevelDeclaration(statement, function (d) { return needExport.has(ts.Debug.assertDefined(d.symbol)); })) {
-                    var exports = addExport(statement, useEs6Exports);
-                    if (exports)
-                        return exports;
+                    var exports_1 = addExport(statement, useEs6Exports);
+                    if (exports_1)
+                        return exports_1;
                 }
                 return statement;
             });
@@ -120414,7 +120413,7 @@ var ts;
             });
             Logger.prototype.write = function (s) {
                 if (this.fd >= 0) {
-                    var buf = Buffer.from ? Buffer.from(s) : new Buffer(s);
+                    var buf = sys.bufferFrom(s);
                     // tslint:disable-next-line no-null-keyword
                     fs.writeSync(this.fd, buf, 0, buf.length, /*position*/ null); // TODO: GH#18217
                 }
@@ -121011,7 +121010,7 @@ var ts;
             sys.watchDirectory = watchDirectorySwallowingException;
         }
         // Override sys.write because fs.writeSync is not reliable on Node 4
-        sys.write = function (s) { return writeMessage(Buffer.from ? Buffer.from(s, "utf8") : new Buffer(s, "utf8")); };
+        sys.write = function (s) { return writeMessage(sys.bufferFrom(s, "utf8")); };
         sys.watchFile = function (fileName, callback) {
             var watchedFile = pollingWatchedFileSet.addFile(fileName, callback);
             return {
diff --git a/lib/tsserverlibrary.js b/lib/tsserverlibrary.js
index f57a336bb35..77de91a63b3 100644
--- a/lib/tsserverlibrary.js
+++ b/lib/tsserverlibrary.js
@@ -3910,7 +3910,7 @@ var ts;
         return parseInt(version.substring(1, dot));
     }
     ts.getNodeMajorVersion = getNodeMajorVersion;
-    // TODO: this is used as if it's certainly defined in many places.
+    // TODO: GH#18217 this is used as if it's certainly defined in many places.
     ts.sys = (function () {
         // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
         // byte order mark from the specified encoding. Using any other byte order mark does
@@ -4019,18 +4019,17 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                // See https://github.com/Microsoft/TypeScript/issues/25652
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 // win32\win64 are case insensitive platforms
                 if (platform === "win32" || platform === "win64") {
@@ -5532,7 +5531,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -29462,8 +29461,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -33435,13 +33434,7 @@ var ts;
                     }
                 }
                 // Use contextual parameter type if one is available
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -50785,12 +50778,12 @@ var ts;
                     // yielded values. The only way to trigger these errors is to try checking its return type.
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0 /* Call */).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -50857,7 +50850,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0 /* Local */, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95 /* _ */;
@@ -50877,14 +50870,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8 /* Private */)) {
-                                addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155 /* Constructor */:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8 /* Private */)) {
-                                    addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -50906,7 +50899,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -50961,7 +50954,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -50978,7 +50971,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 /* NamespaceImport */ ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0 /* Local */, unuseds.length === 1
+                    addDiagnostic(importDecl, 0 /* Local */, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -50997,7 +50990,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -51005,21 +50998,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0 /* Local */, declarations.length === 1
+                    addDiagnostic(declarationList, 0 /* Local */, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 /* VariableStatement */ ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -53597,8 +53590,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -60016,6 +60009,9 @@ var ts;
                 case 203 /* ConditionalExpression */:
                     node = node.condition;
                     continue;
+                case 191 /* TaggedTemplateExpression */:
+                    node = node.tag;
+                    continue;
                 case 189 /* CallExpression */:
                     if (stopAtCallExpressions) {
                         return node;
@@ -82053,7 +82049,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -82545,6 +82541,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json" /* Json */]) : undefined;
         // Map storing if there is emit blocking diagnostics for given input
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
@@ -83693,7 +83690,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -86463,16 +86460,15 @@ var ts;
         };
         // From tsc we want to get already parsed result and hence check for rootFileNames
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -87187,6 +87183,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }
@@ -96588,7 +96585,7 @@ var ts;
             "borrows",
             "callback",
             "class",
-            "classDesc",
+            "classdesc",
             "constant",
             "constructor",
             "constructs",
@@ -96605,16 +96602,16 @@ var ts;
             "external",
             "field",
             "file",
-            "fileOverview",
+            "fileoverview",
             "fires",
             "function",
             "generator",
             "global",
-            "hideConstructor",
+            "hideconstructor",
             "host",
             "ignore",
             "implements",
-            "inheritDoc",
+            "inheritdoc",
             "inner",
             "instance",
             "interface",
@@ -96623,7 +96620,7 @@ var ts;
             "license",
             "listens",
             "member",
-            "memberOf",
+            "memberof",
             "method",
             "mixes",
             "module",
@@ -97215,7 +97212,7 @@ var ts;
         /** Call after calling `startNode` and adding children to it. */
         function endNode() {
             if (parent.children) {
-                mergeChildren(parent.children);
+                mergeChildren(parent.children, parent);
                 sortChildren(parent.children);
             }
             parent = parentsStack.pop();
@@ -97371,7 +97368,7 @@ var ts;
             }
         }
         /** Merge declarations of the same kind. */
-        function mergeChildren(children) {
+        function mergeChildren(children, node) {
             var nameToItems = ts.createMap();
             ts.filterMutate(children, function (child) {
                 var declName = ts.getNameOfDeclaration(child.node);
@@ -97388,7 +97385,7 @@ var ts;
                 if (itemsWithSameName instanceof Array) {
                     for (var _i = 0, itemsWithSameName_1 = itemsWithSameName; _i < itemsWithSameName_1.length; _i++) {
                         var itemWithSameName = itemsWithSameName_1[_i];
-                        if (tryMerge(itemWithSameName, child)) {
+                        if (tryMerge(itemWithSameName, child, node)) {
                             return false;
                         }
                     }
@@ -97397,7 +97394,7 @@ var ts;
                 }
                 else {
                     var itemWithSameName = itemsWithSameName;
-                    if (tryMerge(itemWithSameName, child)) {
+                    if (tryMerge(itemWithSameName, child, node)) {
                         return false;
                     }
                     nameToItems.set(name, [itemWithSameName, child]);
@@ -97405,16 +97402,16 @@ var ts;
                 }
             });
         }
-        function tryMerge(a, b) {
-            if (shouldReallyMerge(a.node, b.node)) {
+        function tryMerge(a, b, parent) {
+            if (shouldReallyMerge(a.node, b.node, parent)) {
                 merge(a, b);
                 return true;
             }
             return false;
         }
         /** a and b have the same name, but they may not be mergeable. */
-        function shouldReallyMerge(a, b) {
-            if (a.kind !== b.kind) {
+        function shouldReallyMerge(a, b, parent) {
+            if (a.kind !== b.kind || a.parent !== b.parent && !(isOwnChild(a, parent) && isOwnChild(b, parent))) {
                 return false;
             }
             switch (a.kind) {
@@ -97429,6 +97426,12 @@ var ts;
                     return true;
             }
         }
+        // We want to merge own children like `I` in in `module A { interface I {} } module A { interface I {} }`
+        // We don't want to merge unrelated children like `m` in `const o = { a: { m() {} }, b: { m() {} } };`
+        function isOwnChild(n, parent) {
+            var par = ts.isModuleBlock(n.parent) ? n.parent.parent : n.parent;
+            return par === parent.node || ts.contains(parent.additionalNodes, par);
+        }
         // We use 1 NavNode to represent 'A.B.C', but there are multiple source nodes.
         // Only merge module nodes that have the same chain. Don't merge 'A.B.C' with 'A'!
         function areSameModule(a, b) {
@@ -97445,7 +97448,7 @@ var ts;
             }
             target.children = ts.concatenate(target.children, source.children);
             if (target.children) {
-                mergeChildren(target.children);
+                mergeChildren(target.children, target);
                 sortChildren(target.children);
             }
         }
@@ -102342,7 +102345,6 @@ var ts;
                 // split comment in lines
                 var startLine = sourceFile.getLineAndCharacterOfPosition(commentRange.pos).line;
                 var endLine = sourceFile.getLineAndCharacterOfPosition(commentRange.end).line;
-                var parts;
                 if (startLine === endLine) {
                     if (!firstLineIsIndented) {
                         // treat as single line comment
@@ -102350,18 +102352,18 @@ var ts;
                     }
                     return;
                 }
-                else {
-                    parts = [];
-                    var startPos = commentRange.pos;
-                    for (var line = startLine; line < endLine; line++) {
-                        var endOfLine = ts.getEndLinePosition(line, sourceFile);
-                        parts.push({ pos: startPos, end: endOfLine });
-                        startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
-                    }
-                    if (indentFinalLine) {
-                        parts.push({ pos: startPos, end: commentRange.end });
-                    }
+                var parts = [];
+                var startPos = commentRange.pos;
+                for (var line = startLine; line < endLine; line++) {
+                    var endOfLine = ts.getEndLinePosition(line, sourceFile);
+                    parts.push({ pos: startPos, end: endOfLine });
+                    startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
                 }
+                if (indentFinalLine) {
+                    parts.push({ pos: startPos, end: commentRange.end });
+                }
+                if (parts.length === 0)
+                    return;
                 var startLinePos = ts.getStartPositionOfLine(startLine, sourceFile);
                 var nonWhitespaceColumnInFirstPart = formatting.SmartIndenter.findFirstNonWhitespaceCharacterAndColumn(startLinePos, parts[0].pos, sourceFile, options);
                 if (indentation === nonWhitespaceColumnInFirstPart.column) {
@@ -102901,6 +102903,9 @@ var ts;
                                 getListIfStartEndIsInListRange(node.parent.parameters, start, end);
                         }
                         case 238 /* ClassDeclaration */:
+                        case 207 /* ClassExpression */:
+                        case 239 /* InterfaceDeclaration */:
+                        case 240 /* TypeAliasDeclaration */:
                             return getListIfStartEndIsInListRange(node.parent.typeParameters, node.getStart(sourceFile), end);
                         case 190 /* NewExpression */:
                         case 189 /* CallExpression */: {
@@ -103110,17 +103115,10 @@ var ts;
             function isControlFlowEndingStatement(kind, parent) {
                 switch (kind) {
                     case 228 /* ReturnStatement */:
-                    case 232 /* ThrowStatement */: {
-                        if (parent.kind !== 216 /* Block */) {
-                            return true;
-                        }
-                        var grandParent = parent.parent;
-                        // In a function, we may want to write inner functions after this.
-                        return !(grandParent && grandParent.kind === 194 /* FunctionExpression */ || grandParent.kind === 237 /* FunctionDeclaration */);
-                    }
+                    case 232 /* ThrowStatement */:
                     case 226 /* ContinueStatement */:
                     case 227 /* BreakStatement */:
-                        return true;
+                        return parent.kind !== 216 /* Block */;
                     default:
                         return false;
                 }
@@ -106503,31 +106501,32 @@ var ts;
             var statement = ts.findAncestor(token, ts.isStatement);
             ts.Debug.assert(statement.getStart(sourceFile) === token.getStart(sourceFile));
             var container = (ts.isBlock(statement.parent) ? statement.parent : statement).parent;
-            switch (container.kind) {
-                case 220 /* IfStatement */:
-                    if (container.elseStatement) {
-                        if (ts.isBlock(statement.parent)) {
-                            changes.deleteNodeRange(sourceFile, ts.first(statement.parent.statements), ts.last(statement.parent.statements));
+            if (!ts.isBlock(statement.parent) || statement === ts.first(statement.parent.statements)) {
+                switch (container.kind) {
+                    case 220 /* IfStatement */:
+                        if (container.elseStatement) {
+                            if (ts.isBlock(statement.parent)) {
+                                break;
+                            }
+                            else {
+                                changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
+                            }
+                            return;
                         }
-                        else {
-                            changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
-                        }
-                        break;
-                    }
-                // falls through
-                case 222 /* WhileStatement */:
-                case 223 /* ForStatement */:
-                    changes.delete(sourceFile, container);
-                    break;
-                default:
-                    if (ts.isBlock(statement.parent)) {
-                        var end_2 = start + length;
-                        var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
-                        changes.deleteNodeRange(sourceFile, statement, lastStatement);
-                    }
-                    else {
-                        changes.delete(sourceFile, statement);
-                    }
+                    // falls through
+                    case 222 /* WhileStatement */:
+                    case 223 /* ForStatement */:
+                        changes.delete(sourceFile, container);
+                        return;
+                }
+            }
+            if (ts.isBlock(statement.parent)) {
+                var end_2 = start + length;
+                var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
+                changes.deleteNodeRange(sourceFile, statement, lastStatement);
+            }
+            else {
+                changes.delete(sourceFile, statement);
             }
         }
         function lastWhere(a, pred) {
diff --git a/lib/typescript.js b/lib/typescript.js
index 3808987a217..964a18d2006 100644
--- a/lib/typescript.js
+++ b/lib/typescript.js
@@ -3910,7 +3910,7 @@ var ts;
         return parseInt(version.substring(1, dot));
     }
     ts.getNodeMajorVersion = getNodeMajorVersion;
-    // TODO: this is used as if it's certainly defined in many places.
+    // TODO: GH#18217 this is used as if it's certainly defined in many places.
     ts.sys = (function () {
         // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
         // byte order mark from the specified encoding. Using any other byte order mark does
@@ -4019,18 +4019,17 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                // See https://github.com/Microsoft/TypeScript/issues/25652
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 // win32\win64 are case insensitive platforms
                 if (platform === "win32" || platform === "win64") {
@@ -5532,7 +5531,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -29462,8 +29461,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -33435,13 +33434,7 @@ var ts;
                     }
                 }
                 // Use contextual parameter type if one is available
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -50785,12 +50778,12 @@ var ts;
                     // yielded values. The only way to trigger these errors is to try checking its return type.
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0 /* Call */).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -50857,7 +50850,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0 /* Local */, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95 /* _ */;
@@ -50877,14 +50870,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8 /* Private */)) {
-                                addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155 /* Constructor */:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8 /* Private */)) {
-                                    addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -50906,7 +50899,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -50961,7 +50954,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -50978,7 +50971,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 /* NamespaceImport */ ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0 /* Local */, unuseds.length === 1
+                    addDiagnostic(importDecl, 0 /* Local */, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -50997,7 +50990,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -51005,21 +50998,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0 /* Local */, declarations.length === 1
+                    addDiagnostic(declarationList, 0 /* Local */, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 /* VariableStatement */ ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -53597,8 +53590,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -60016,6 +60009,9 @@ var ts;
                 case 203 /* ConditionalExpression */:
                     node = node.condition;
                     continue;
+                case 191 /* TaggedTemplateExpression */:
+                    node = node.tag;
+                    continue;
                 case 189 /* CallExpression */:
                     if (stopAtCallExpressions) {
                         return node;
@@ -82053,7 +82049,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -82545,6 +82541,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json" /* Json */]) : undefined;
         // Map storing if there is emit blocking diagnostics for given input
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
@@ -83693,7 +83690,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -86463,16 +86460,15 @@ var ts;
         };
         // From tsc we want to get already parsed result and hence check for rootFileNames
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -87187,6 +87183,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }
@@ -96588,7 +96585,7 @@ var ts;
             "borrows",
             "callback",
             "class",
-            "classDesc",
+            "classdesc",
             "constant",
             "constructor",
             "constructs",
@@ -96605,16 +96602,16 @@ var ts;
             "external",
             "field",
             "file",
-            "fileOverview",
+            "fileoverview",
             "fires",
             "function",
             "generator",
             "global",
-            "hideConstructor",
+            "hideconstructor",
             "host",
             "ignore",
             "implements",
-            "inheritDoc",
+            "inheritdoc",
             "inner",
             "instance",
             "interface",
@@ -96623,7 +96620,7 @@ var ts;
             "license",
             "listens",
             "member",
-            "memberOf",
+            "memberof",
             "method",
             "mixes",
             "module",
@@ -97215,7 +97212,7 @@ var ts;
         /** Call after calling `startNode` and adding children to it. */
         function endNode() {
             if (parent.children) {
-                mergeChildren(parent.children);
+                mergeChildren(parent.children, parent);
                 sortChildren(parent.children);
             }
             parent = parentsStack.pop();
@@ -97371,7 +97368,7 @@ var ts;
             }
         }
         /** Merge declarations of the same kind. */
-        function mergeChildren(children) {
+        function mergeChildren(children, node) {
             var nameToItems = ts.createMap();
             ts.filterMutate(children, function (child) {
                 var declName = ts.getNameOfDeclaration(child.node);
@@ -97388,7 +97385,7 @@ var ts;
                 if (itemsWithSameName instanceof Array) {
                     for (var _i = 0, itemsWithSameName_1 = itemsWithSameName; _i < itemsWithSameName_1.length; _i++) {
                         var itemWithSameName = itemsWithSameName_1[_i];
-                        if (tryMerge(itemWithSameName, child)) {
+                        if (tryMerge(itemWithSameName, child, node)) {
                             return false;
                         }
                     }
@@ -97397,7 +97394,7 @@ var ts;
                 }
                 else {
                     var itemWithSameName = itemsWithSameName;
-                    if (tryMerge(itemWithSameName, child)) {
+                    if (tryMerge(itemWithSameName, child, node)) {
                         return false;
                     }
                     nameToItems.set(name, [itemWithSameName, child]);
@@ -97405,16 +97402,16 @@ var ts;
                 }
             });
         }
-        function tryMerge(a, b) {
-            if (shouldReallyMerge(a.node, b.node)) {
+        function tryMerge(a, b, parent) {
+            if (shouldReallyMerge(a.node, b.node, parent)) {
                 merge(a, b);
                 return true;
             }
             return false;
         }
         /** a and b have the same name, but they may not be mergeable. */
-        function shouldReallyMerge(a, b) {
-            if (a.kind !== b.kind) {
+        function shouldReallyMerge(a, b, parent) {
+            if (a.kind !== b.kind || a.parent !== b.parent && !(isOwnChild(a, parent) && isOwnChild(b, parent))) {
                 return false;
             }
             switch (a.kind) {
@@ -97429,6 +97426,12 @@ var ts;
                     return true;
             }
         }
+        // We want to merge own children like `I` in in `module A { interface I {} } module A { interface I {} }`
+        // We don't want to merge unrelated children like `m` in `const o = { a: { m() {} }, b: { m() {} } };`
+        function isOwnChild(n, parent) {
+            var par = ts.isModuleBlock(n.parent) ? n.parent.parent : n.parent;
+            return par === parent.node || ts.contains(parent.additionalNodes, par);
+        }
         // We use 1 NavNode to represent 'A.B.C', but there are multiple source nodes.
         // Only merge module nodes that have the same chain. Don't merge 'A.B.C' with 'A'!
         function areSameModule(a, b) {
@@ -97445,7 +97448,7 @@ var ts;
             }
             target.children = ts.concatenate(target.children, source.children);
             if (target.children) {
-                mergeChildren(target.children);
+                mergeChildren(target.children, target);
                 sortChildren(target.children);
             }
         }
@@ -102342,7 +102345,6 @@ var ts;
                 // split comment in lines
                 var startLine = sourceFile.getLineAndCharacterOfPosition(commentRange.pos).line;
                 var endLine = sourceFile.getLineAndCharacterOfPosition(commentRange.end).line;
-                var parts;
                 if (startLine === endLine) {
                     if (!firstLineIsIndented) {
                         // treat as single line comment
@@ -102350,18 +102352,18 @@ var ts;
                     }
                     return;
                 }
-                else {
-                    parts = [];
-                    var startPos = commentRange.pos;
-                    for (var line = startLine; line < endLine; line++) {
-                        var endOfLine = ts.getEndLinePosition(line, sourceFile);
-                        parts.push({ pos: startPos, end: endOfLine });
-                        startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
-                    }
-                    if (indentFinalLine) {
-                        parts.push({ pos: startPos, end: commentRange.end });
-                    }
+                var parts = [];
+                var startPos = commentRange.pos;
+                for (var line = startLine; line < endLine; line++) {
+                    var endOfLine = ts.getEndLinePosition(line, sourceFile);
+                    parts.push({ pos: startPos, end: endOfLine });
+                    startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
                 }
+                if (indentFinalLine) {
+                    parts.push({ pos: startPos, end: commentRange.end });
+                }
+                if (parts.length === 0)
+                    return;
                 var startLinePos = ts.getStartPositionOfLine(startLine, sourceFile);
                 var nonWhitespaceColumnInFirstPart = formatting.SmartIndenter.findFirstNonWhitespaceCharacterAndColumn(startLinePos, parts[0].pos, sourceFile, options);
                 if (indentation === nonWhitespaceColumnInFirstPart.column) {
@@ -102901,6 +102903,9 @@ var ts;
                                 getListIfStartEndIsInListRange(node.parent.parameters, start, end);
                         }
                         case 238 /* ClassDeclaration */:
+                        case 207 /* ClassExpression */:
+                        case 239 /* InterfaceDeclaration */:
+                        case 240 /* TypeAliasDeclaration */:
                             return getListIfStartEndIsInListRange(node.parent.typeParameters, node.getStart(sourceFile), end);
                         case 190 /* NewExpression */:
                         case 189 /* CallExpression */: {
@@ -103110,17 +103115,10 @@ var ts;
             function isControlFlowEndingStatement(kind, parent) {
                 switch (kind) {
                     case 228 /* ReturnStatement */:
-                    case 232 /* ThrowStatement */: {
-                        if (parent.kind !== 216 /* Block */) {
-                            return true;
-                        }
-                        var grandParent = parent.parent;
-                        // In a function, we may want to write inner functions after this.
-                        return !(grandParent && grandParent.kind === 194 /* FunctionExpression */ || grandParent.kind === 237 /* FunctionDeclaration */);
-                    }
+                    case 232 /* ThrowStatement */:
                     case 226 /* ContinueStatement */:
                     case 227 /* BreakStatement */:
-                        return true;
+                        return parent.kind !== 216 /* Block */;
                     default:
                         return false;
                 }
@@ -106503,31 +106501,32 @@ var ts;
             var statement = ts.findAncestor(token, ts.isStatement);
             ts.Debug.assert(statement.getStart(sourceFile) === token.getStart(sourceFile));
             var container = (ts.isBlock(statement.parent) ? statement.parent : statement).parent;
-            switch (container.kind) {
-                case 220 /* IfStatement */:
-                    if (container.elseStatement) {
-                        if (ts.isBlock(statement.parent)) {
-                            changes.deleteNodeRange(sourceFile, ts.first(statement.parent.statements), ts.last(statement.parent.statements));
+            if (!ts.isBlock(statement.parent) || statement === ts.first(statement.parent.statements)) {
+                switch (container.kind) {
+                    case 220 /* IfStatement */:
+                        if (container.elseStatement) {
+                            if (ts.isBlock(statement.parent)) {
+                                break;
+                            }
+                            else {
+                                changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
+                            }
+                            return;
                         }
-                        else {
-                            changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
-                        }
-                        break;
-                    }
-                // falls through
-                case 222 /* WhileStatement */:
-                case 223 /* ForStatement */:
-                    changes.delete(sourceFile, container);
-                    break;
-                default:
-                    if (ts.isBlock(statement.parent)) {
-                        var end_2 = start + length;
-                        var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
-                        changes.deleteNodeRange(sourceFile, statement, lastStatement);
-                    }
-                    else {
-                        changes.delete(sourceFile, statement);
-                    }
+                    // falls through
+                    case 222 /* WhileStatement */:
+                    case 223 /* ForStatement */:
+                        changes.delete(sourceFile, container);
+                        return;
+                }
+            }
+            if (ts.isBlock(statement.parent)) {
+                var end_2 = start + length;
+                var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
+                changes.deleteNodeRange(sourceFile, statement, lastStatement);
+            }
+            else {
+                changes.delete(sourceFile, statement);
             }
         }
         function lastWhere(a, pred) {
diff --git a/lib/typescriptServices.js b/lib/typescriptServices.js
index 3808987a217..964a18d2006 100644
--- a/lib/typescriptServices.js
+++ b/lib/typescriptServices.js
@@ -3910,7 +3910,7 @@ var ts;
         return parseInt(version.substring(1, dot));
     }
     ts.getNodeMajorVersion = getNodeMajorVersion;
-    // TODO: this is used as if it's certainly defined in many places.
+    // TODO: GH#18217 this is used as if it's certainly defined in many places.
     ts.sys = (function () {
         // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
         // byte order mark from the specified encoding. Using any other byte order mark does
@@ -4019,18 +4019,17 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                // See https://github.com/Microsoft/TypeScript/issues/25652
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 // win32\win64 are case insensitive platforms
                 if (platform === "win32" || platform === "win64") {
@@ -5532,7 +5531,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -29462,8 +29461,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -33435,13 +33434,7 @@ var ts;
                     }
                 }
                 // Use contextual parameter type if one is available
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -50785,12 +50778,12 @@ var ts;
                     // yielded values. The only way to trigger these errors is to try checking its return type.
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0 /* Call */).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -50857,7 +50850,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0 /* Local */, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95 /* _ */;
@@ -50877,14 +50870,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8 /* Private */)) {
-                                addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155 /* Constructor */:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8 /* Private */)) {
-                                    addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -50906,7 +50899,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -50961,7 +50954,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -50978,7 +50971,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 /* NamespaceImport */ ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0 /* Local */, unuseds.length === 1
+                    addDiagnostic(importDecl, 0 /* Local */, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -50997,7 +50990,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -51005,21 +50998,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0 /* Local */, declarations.length === 1
+                    addDiagnostic(declarationList, 0 /* Local */, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 /* VariableStatement */ ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -53597,8 +53590,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -60016,6 +60009,9 @@ var ts;
                 case 203 /* ConditionalExpression */:
                     node = node.condition;
                     continue;
+                case 191 /* TaggedTemplateExpression */:
+                    node = node.tag;
+                    continue;
                 case 189 /* CallExpression */:
                     if (stopAtCallExpressions) {
                         return node;
@@ -82053,7 +82049,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -82545,6 +82541,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json" /* Json */]) : undefined;
         // Map storing if there is emit blocking diagnostics for given input
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
@@ -83693,7 +83690,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -86463,16 +86460,15 @@ var ts;
         };
         // From tsc we want to get already parsed result and hence check for rootFileNames
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -87187,6 +87183,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }
@@ -96588,7 +96585,7 @@ var ts;
             "borrows",
             "callback",
             "class",
-            "classDesc",
+            "classdesc",
             "constant",
             "constructor",
             "constructs",
@@ -96605,16 +96602,16 @@ var ts;
             "external",
             "field",
             "file",
-            "fileOverview",
+            "fileoverview",
             "fires",
             "function",
             "generator",
             "global",
-            "hideConstructor",
+            "hideconstructor",
             "host",
             "ignore",
             "implements",
-            "inheritDoc",
+            "inheritdoc",
             "inner",
             "instance",
             "interface",
@@ -96623,7 +96620,7 @@ var ts;
             "license",
             "listens",
             "member",
-            "memberOf",
+            "memberof",
             "method",
             "mixes",
             "module",
@@ -97215,7 +97212,7 @@ var ts;
         /** Call after calling `startNode` and adding children to it. */
         function endNode() {
             if (parent.children) {
-                mergeChildren(parent.children);
+                mergeChildren(parent.children, parent);
                 sortChildren(parent.children);
             }
             parent = parentsStack.pop();
@@ -97371,7 +97368,7 @@ var ts;
             }
         }
         /** Merge declarations of the same kind. */
-        function mergeChildren(children) {
+        function mergeChildren(children, node) {
             var nameToItems = ts.createMap();
             ts.filterMutate(children, function (child) {
                 var declName = ts.getNameOfDeclaration(child.node);
@@ -97388,7 +97385,7 @@ var ts;
                 if (itemsWithSameName instanceof Array) {
                     for (var _i = 0, itemsWithSameName_1 = itemsWithSameName; _i < itemsWithSameName_1.length; _i++) {
                         var itemWithSameName = itemsWithSameName_1[_i];
-                        if (tryMerge(itemWithSameName, child)) {
+                        if (tryMerge(itemWithSameName, child, node)) {
                             return false;
                         }
                     }
@@ -97397,7 +97394,7 @@ var ts;
                 }
                 else {
                     var itemWithSameName = itemsWithSameName;
-                    if (tryMerge(itemWithSameName, child)) {
+                    if (tryMerge(itemWithSameName, child, node)) {
                         return false;
                     }
                     nameToItems.set(name, [itemWithSameName, child]);
@@ -97405,16 +97402,16 @@ var ts;
                 }
             });
         }
-        function tryMerge(a, b) {
-            if (shouldReallyMerge(a.node, b.node)) {
+        function tryMerge(a, b, parent) {
+            if (shouldReallyMerge(a.node, b.node, parent)) {
                 merge(a, b);
                 return true;
             }
             return false;
         }
         /** a and b have the same name, but they may not be mergeable. */
-        function shouldReallyMerge(a, b) {
-            if (a.kind !== b.kind) {
+        function shouldReallyMerge(a, b, parent) {
+            if (a.kind !== b.kind || a.parent !== b.parent && !(isOwnChild(a, parent) && isOwnChild(b, parent))) {
                 return false;
             }
             switch (a.kind) {
@@ -97429,6 +97426,12 @@ var ts;
                     return true;
             }
         }
+        // We want to merge own children like `I` in in `module A { interface I {} } module A { interface I {} }`
+        // We don't want to merge unrelated children like `m` in `const o = { a: { m() {} }, b: { m() {} } };`
+        function isOwnChild(n, parent) {
+            var par = ts.isModuleBlock(n.parent) ? n.parent.parent : n.parent;
+            return par === parent.node || ts.contains(parent.additionalNodes, par);
+        }
         // We use 1 NavNode to represent 'A.B.C', but there are multiple source nodes.
         // Only merge module nodes that have the same chain. Don't merge 'A.B.C' with 'A'!
         function areSameModule(a, b) {
@@ -97445,7 +97448,7 @@ var ts;
             }
             target.children = ts.concatenate(target.children, source.children);
             if (target.children) {
-                mergeChildren(target.children);
+                mergeChildren(target.children, target);
                 sortChildren(target.children);
             }
         }
@@ -102342,7 +102345,6 @@ var ts;
                 // split comment in lines
                 var startLine = sourceFile.getLineAndCharacterOfPosition(commentRange.pos).line;
                 var endLine = sourceFile.getLineAndCharacterOfPosition(commentRange.end).line;
-                var parts;
                 if (startLine === endLine) {
                     if (!firstLineIsIndented) {
                         // treat as single line comment
@@ -102350,18 +102352,18 @@ var ts;
                     }
                     return;
                 }
-                else {
-                    parts = [];
-                    var startPos = commentRange.pos;
-                    for (var line = startLine; line < endLine; line++) {
-                        var endOfLine = ts.getEndLinePosition(line, sourceFile);
-                        parts.push({ pos: startPos, end: endOfLine });
-                        startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
-                    }
-                    if (indentFinalLine) {
-                        parts.push({ pos: startPos, end: commentRange.end });
-                    }
+                var parts = [];
+                var startPos = commentRange.pos;
+                for (var line = startLine; line < endLine; line++) {
+                    var endOfLine = ts.getEndLinePosition(line, sourceFile);
+                    parts.push({ pos: startPos, end: endOfLine });
+                    startPos = ts.getStartPositionOfLine(line + 1, sourceFile);
                 }
+                if (indentFinalLine) {
+                    parts.push({ pos: startPos, end: commentRange.end });
+                }
+                if (parts.length === 0)
+                    return;
                 var startLinePos = ts.getStartPositionOfLine(startLine, sourceFile);
                 var nonWhitespaceColumnInFirstPart = formatting.SmartIndenter.findFirstNonWhitespaceCharacterAndColumn(startLinePos, parts[0].pos, sourceFile, options);
                 if (indentation === nonWhitespaceColumnInFirstPart.column) {
@@ -102901,6 +102903,9 @@ var ts;
                                 getListIfStartEndIsInListRange(node.parent.parameters, start, end);
                         }
                         case 238 /* ClassDeclaration */:
+                        case 207 /* ClassExpression */:
+                        case 239 /* InterfaceDeclaration */:
+                        case 240 /* TypeAliasDeclaration */:
                             return getListIfStartEndIsInListRange(node.parent.typeParameters, node.getStart(sourceFile), end);
                         case 190 /* NewExpression */:
                         case 189 /* CallExpression */: {
@@ -103110,17 +103115,10 @@ var ts;
             function isControlFlowEndingStatement(kind, parent) {
                 switch (kind) {
                     case 228 /* ReturnStatement */:
-                    case 232 /* ThrowStatement */: {
-                        if (parent.kind !== 216 /* Block */) {
-                            return true;
-                        }
-                        var grandParent = parent.parent;
-                        // In a function, we may want to write inner functions after this.
-                        return !(grandParent && grandParent.kind === 194 /* FunctionExpression */ || grandParent.kind === 237 /* FunctionDeclaration */);
-                    }
+                    case 232 /* ThrowStatement */:
                     case 226 /* ContinueStatement */:
                     case 227 /* BreakStatement */:
-                        return true;
+                        return parent.kind !== 216 /* Block */;
                     default:
                         return false;
                 }
@@ -106503,31 +106501,32 @@ var ts;
             var statement = ts.findAncestor(token, ts.isStatement);
             ts.Debug.assert(statement.getStart(sourceFile) === token.getStart(sourceFile));
             var container = (ts.isBlock(statement.parent) ? statement.parent : statement).parent;
-            switch (container.kind) {
-                case 220 /* IfStatement */:
-                    if (container.elseStatement) {
-                        if (ts.isBlock(statement.parent)) {
-                            changes.deleteNodeRange(sourceFile, ts.first(statement.parent.statements), ts.last(statement.parent.statements));
+            if (!ts.isBlock(statement.parent) || statement === ts.first(statement.parent.statements)) {
+                switch (container.kind) {
+                    case 220 /* IfStatement */:
+                        if (container.elseStatement) {
+                            if (ts.isBlock(statement.parent)) {
+                                break;
+                            }
+                            else {
+                                changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
+                            }
+                            return;
                         }
-                        else {
-                            changes.replaceNode(sourceFile, statement, ts.createBlock(ts.emptyArray));
-                        }
-                        break;
-                    }
-                // falls through
-                case 222 /* WhileStatement */:
-                case 223 /* ForStatement */:
-                    changes.delete(sourceFile, container);
-                    break;
-                default:
-                    if (ts.isBlock(statement.parent)) {
-                        var end_2 = start + length;
-                        var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
-                        changes.deleteNodeRange(sourceFile, statement, lastStatement);
-                    }
-                    else {
-                        changes.delete(sourceFile, statement);
-                    }
+                    // falls through
+                    case 222 /* WhileStatement */:
+                    case 223 /* ForStatement */:
+                        changes.delete(sourceFile, container);
+                        return;
+                }
+            }
+            if (ts.isBlock(statement.parent)) {
+                var end_2 = start + length;
+                var lastStatement = ts.Debug.assertDefined(lastWhere(ts.sliceAfter(statement.parent.statements, statement), function (s) { return s.pos < end_2; }));
+                changes.deleteNodeRange(sourceFile, statement, lastStatement);
+            }
+            else {
+                changes.delete(sourceFile, statement);
             }
         }
         function lastWhere(a, pred) {
diff --git a/lib/typingsInstaller.js b/lib/typingsInstaller.js
index 780f5c4d13d..e39d2a9a58a 100644
--- a/lib/typingsInstaller.js
+++ b/lib/typingsInstaller.js
@@ -3923,7 +3923,7 @@ var ts;
         return parseInt(version.substring(1, dot));
     }
     ts.getNodeMajorVersion = getNodeMajorVersion;
-    // TODO: this is used as if it's certainly defined in many places.
+    // TODO: GH#18217 this is used as if it's certainly defined in many places.
     ts.sys = (function () {
         // NodeJS detects "\uFEFF" at the start of the string and *replaces* it with the actual
         // byte order mark from the specified encoding. Using any other byte order mark does
@@ -4032,18 +4032,17 @@ var ts;
                         process.stdout._handle.setBlocking(true);
                     }
                 },
-                base64decode: Buffer.from ? function (input) {
-                    return Buffer.from(input, "base64").toString("utf8");
-                } : function (input) {
-                    return new Buffer(input, "base64").toString("utf8");
-                },
-                base64encode: Buffer.from ? function (input) {
-                    return Buffer.from(input).toString("base64");
-                } : function (input) {
-                    return new Buffer(input).toString("base64");
-                }
+                bufferFrom: bufferFrom,
+                base64decode: function (input) { return bufferFrom(input, "base64").toString("utf8"); },
+                base64encode: function (input) { return bufferFrom(input).toString("base64"); },
             };
             return nodeSystem;
+            function bufferFrom(input, encoding) {
+                // See https://github.com/Microsoft/TypeScript/issues/25652
+                return Buffer.from && Buffer.from !== Int8Array.from
+                    ? Buffer.from(input, encoding)
+                    : new Buffer(input, encoding);
+            }
             function isFileSystemCaseSensitive() {
                 // win32\win64 are case insensitive platforms
                 if (platform === "win32" || platform === "win64") {
@@ -5545,7 +5544,7 @@ var ts;
         Expected_0_1_type_arguments_provide_these_with_an_extends_tag: diag(8027, ts.DiagnosticCategory.Error, "Expected_0_1_type_arguments_provide_these_with_an_extends_tag_8027", "Expected {0}-{1} type arguments; provide these with an '@extends' tag."),
         JSDoc_may_only_appear_in_the_last_parameter_of_a_signature: diag(8028, ts.DiagnosticCategory.Error, "JSDoc_may_only_appear_in_the_last_parameter_of_a_signature_8028", "JSDoc '...' may only appear in the last parameter of a signature."),
         JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_had_an_array_type: diag(8029, ts.DiagnosticCategory.Error, "JSDoc_param_tag_has_name_0_but_there_is_no_parameter_with_that_name_It_would_match_arguments_if_it_h_8029", "JSDoc '@param' tag has name '{0}', but there is no parameter with that name. It would match 'arguments' if it had an array type."),
-        The_type_of_a_function_declaration_must_be_callable: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_be_callable_8030", "The type of a function declaration must be callable."),
+        The_type_of_a_function_declaration_must_match_the_function_s_signature: diag(8030, ts.DiagnosticCategory.Error, "The_type_of_a_function_declaration_must_match_the_function_s_signature_8030", "The type of a function declaration must match the function's signature."),
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clause: diag(9002, ts.DiagnosticCategory.Error, "Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_clas_9002", "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause."),
         class_expressions_are_not_currently_supported: diag(9003, ts.DiagnosticCategory.Error, "class_expressions_are_not_currently_supported_9003", "'class' expressions are not currently supported."),
         Language_service_is_disabled: diag(9004, ts.DiagnosticCategory.Error, "Language_service_is_disabled_9004", "Language service is disabled."),
@@ -29475,8 +29474,8 @@ var ts;
                     cancellationToken = undefined;
                 }
                 function addUnusedDiagnostics() {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (kind, diag) {
-                        if (!unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(file), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && !unusedIsError(kind)) {
                             (diagnostics || (diagnostics = [])).push(__assign({}, diag, { category: ts.DiagnosticCategory.Suggestion }));
                         }
                     });
@@ -33448,13 +33447,7 @@ var ts;
                     }
                 }
                 // Use contextual parameter type if one is available
-                var type = void 0;
-                if (declaration.symbol.escapedName === "this") {
-                    type = getContextualThisParameterType(func);
-                }
-                else {
-                    type = getContextuallyTypedParameterType(declaration);
-                }
+                var type = declaration.symbol.escapedName === "this" ? getContextualThisParameterType(func) : getContextuallyTypedParameterType(declaration);
                 if (type) {
                     return addOptionality(type, isOptional);
                 }
@@ -50798,12 +50791,12 @@ var ts;
                     // yielded values. The only way to trigger these errors is to try checking its return type.
                     getReturnTypeOfSignature(getSignatureFromDeclaration(node));
                 }
-                // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
-                if (ts.isInJavaScriptFile(node)) {
-                    var typeTag = ts.getJSDocTypeTag(node);
-                    if (typeTag && typeTag.typeExpression && !getSignaturesOfType(getTypeFromTypeNode(typeTag.typeExpression), 0 /* Call */).length) {
-                        error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_be_callable);
-                    }
+            }
+            // A js function declaration can have a @type tag instead of a return type node, but that type must have a call signature
+            if (ts.isInJavaScriptFile(node)) {
+                var typeTag = ts.getJSDocTypeTag(node);
+                if (typeTag && typeTag.typeExpression && !getContextualCallSignature(getTypeFromTypeNode(typeTag.typeExpression), node)) {
+                    error(typeTag, ts.Diagnostics.The_type_of_a_function_declaration_must_match_the_function_s_signature);
                 }
             }
         }
@@ -50870,7 +50863,7 @@ var ts;
         function errorUnusedLocal(declaration, name, addDiagnostic) {
             var node = ts.getNameOfDeclaration(declaration) || declaration;
             var message = isTypeDeclaration(declaration) ? ts.Diagnostics._0_is_declared_but_never_used : ts.Diagnostics._0_is_declared_but_its_value_is_never_read;
-            addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(node, message, name));
+            addDiagnostic(declaration, 0 /* Local */, ts.createDiagnosticForNode(node, message, name));
         }
         function isIdentifierThatStartsWithUnderscore(node) {
             return ts.isIdentifier(node) && ts.idText(node).charCodeAt(0) === 95 /* _ */;
@@ -50890,14 +50883,14 @@ var ts;
                             }
                             var symbol = getSymbolOfNode(member);
                             if (!symbol.isReferenced && ts.hasModifier(member, 8 /* Private */)) {
-                                addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
+                                addDiagnostic(member, 0 /* Local */, ts.createDiagnosticForNode(member.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, symbolToString(symbol)));
                             }
                             break;
                         case 155 /* Constructor */:
                             for (var _b = 0, _c = member.parameters; _b < _c.length; _b++) {
                                 var parameter = _c[_b];
                                 if (!parameter.symbol.isReferenced && ts.hasModifier(parameter, 8 /* Private */)) {
-                                    addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
+                                    addDiagnostic(parameter, 0 /* Local */, ts.createDiagnosticForNode(parameter.name, ts.Diagnostics.Property_0_is_declared_but_its_value_is_never_read, ts.symbolName(parameter.symbol)));
                                 }
                             }
                             break;
@@ -50919,7 +50912,7 @@ var ts;
                 for (var _i = 0, typeParameters_2 = typeParameters; _i < typeParameters_2.length; _i++) {
                     var typeParameter = typeParameters_2[_i];
                     if (!(getMergedSymbol(typeParameter.symbol).isReferenced & 262144 /* TypeParameter */) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
-                        addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
+                        addDiagnostic(typeParameter, 1 /* Parameter */, ts.createDiagnosticForNode(typeParameter.name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(typeParameter.symbol)));
                     }
                 }
             }
@@ -50974,7 +50967,7 @@ var ts;
                         var name = local.valueDeclaration && ts.getNameOfDeclaration(local.valueDeclaration);
                         if (parameter && name) {
                             if (!ts.isParameterPropertyDeclaration(parameter) && !ts.parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
-                                addDiagnostic(1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
+                                addDiagnostic(parameter, 1 /* Parameter */, ts.createDiagnosticForNode(name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.symbolName(local)));
                             }
                         }
                         else {
@@ -50991,7 +50984,7 @@ var ts;
                         (importClause.namedBindings.kind === 249 /* NamespaceImport */ ? 1 : importClause.namedBindings.elements.length)
                         : 0);
                 if (nDeclarations === unuseds.length) {
-                    addDiagnostic(0 /* Local */, unuseds.length === 1
+                    addDiagnostic(importDecl, 0 /* Local */, unuseds.length === 1
                         ? ts.createDiagnosticForNode(importDecl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.first(unuseds).name))
                         : ts.createDiagnosticForNode(importDecl, ts.Diagnostics.All_imports_in_import_declaration_are_unused));
                 }
@@ -51010,7 +51003,7 @@ var ts;
                         addToGroup(unusedVariables, bindingPattern.parent.parent, bindingPattern.parent, getNodeId);
                     }
                     else {
-                        addDiagnostic(kind, bindingElements.length === 1
+                        addDiagnostic(bindingPattern, kind, bindingElements.length === 1
                             ? ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(ts.first(bindingElements).name, ts.isIdentifier)))
                             : ts.createDiagnosticForNode(bindingPattern, ts.Diagnostics.All_destructured_elements_are_unused));
                     }
@@ -51018,21 +51011,21 @@ var ts;
                 else {
                     for (var _i = 0, bindingElements_1 = bindingElements; _i < bindingElements_1.length; _i++) {
                         var e = bindingElements_1[_i];
-                        addDiagnostic(kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
+                        addDiagnostic(e, kind, ts.createDiagnosticForNode(e, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(e.name, ts.isIdentifier))));
                     }
                 }
             });
             unusedVariables.forEach(function (_a) {
                 var declarationList = _a[0], declarations = _a[1];
                 if (declarationList.declarations.length === declarations.length) {
-                    addDiagnostic(0 /* Local */, declarations.length === 1
+                    addDiagnostic(declarationList, 0 /* Local */, declarations.length === 1
                         ? ts.createDiagnosticForNode(ts.first(declarations).name, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, bindingNameText(ts.first(declarations).name))
                         : ts.createDiagnosticForNode(declarationList.parent.kind === 217 /* VariableStatement */ ? declarationList.parent : declarationList, ts.Diagnostics.All_variables_are_unused));
                 }
                 else {
                     for (var _i = 0, declarations_5 = declarations; _i < declarations_5.length; _i++) {
                         var decl = declarations_5[_i];
-                        addDiagnostic(0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
+                        addDiagnostic(decl, 0 /* Local */, ts.createDiagnosticForNode(decl, ts.Diagnostics._0_is_declared_but_its_value_is_never_read, ts.idText(ts.cast(decl.name, ts.isIdentifier))));
                     }
                 }
             });
@@ -53610,8 +53603,8 @@ var ts;
                     registerForUnusedIdentifiersCheck(node);
                 }
                 if (!node.isDeclarationFile && (compilerOptions.noUnusedLocals || compilerOptions.noUnusedParameters)) {
-                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (kind, diag) {
-                        if (unusedIsError(kind)) {
+                    checkUnusedIdentifiers(getPotentiallyUnusedIdentifiers(node), function (containingNode, kind, diag) {
+                        if (!ts.containsParseError(containingNode) && unusedIsError(kind)) {
                             diagnostics.add(diag);
                         }
                     });
@@ -60029,6 +60022,9 @@ var ts;
                 case 203 /* ConditionalExpression */:
                     node = node.condition;
                     continue;
+                case 191 /* TaggedTemplateExpression */:
+                    node = node.tag;
+                    continue;
                 case 189 /* CallExpression */:
                     if (stopAtCallExpressions) {
                         return node;
@@ -82066,7 +82062,7 @@ var ts;
     }
     function createFileWatcherWithTriggerLogging(host, file, cb, flags, passThrough, detailInfo1, detailInfo2, addWatch, log, watchCaption, getDetailWatchInfo) {
         return addWatch(host, file, function (fileName, cbOptional) {
-            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
+            var triggerredInfo = watchCaption + ":: Triggered with " + fileName + " " + (cbOptional !== undefined ? cbOptional : "") + ":: " + getWatchInfo(file, flags, detailInfo1, detailInfo2, getDetailWatchInfo);
             log(triggerredInfo);
             var start = ts.timestamp();
             cb(fileName, cbOptional, passThrough);
@@ -82558,6 +82554,7 @@ var ts;
         var programDiagnostics = ts.createDiagnosticCollection();
         var currentDirectory = host.getCurrentDirectory();
         var supportedExtensions = ts.getSupportedExtensions(options);
+        var supportedExtensionsWithJsonIfResolveJsonModule = options.resolveJsonModule ? supportedExtensions.concat([".json" /* Json */]) : undefined;
         // Map storing if there is emit blocking diagnostics for given input
         var hasEmitBlockingDiagnostics = ts.createMap();
         var _compilerOptionsObjectLiteralSyntax;
@@ -83706,7 +83703,7 @@ var ts;
         }
         function getSourceFileFromReferenceWorker(fileName, getSourceFile, fail, refFile) {
             if (ts.hasExtension(fileName)) {
-                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
+                if (!options.allowNonTsExtensions && !ts.forEach(supportedExtensionsWithJsonIfResolveJsonModule || supportedExtensions, function (extension) { return ts.fileExtensionIs(host.getCanonicalFileName(fileName), extension); })) {
                     if (fail)
                         fail(ts.Diagnostics.File_0_has_unsupported_extension_The_only_supported_extensions_are_1, fileName, "'" + supportedExtensions.join("', '") + "'");
                     return undefined;
@@ -86476,16 +86473,15 @@ var ts;
         };
         // From tsc we want to get already parsed result and hence check for rootFileNames
         var newLine = updateNewLine();
+        if (configFileName && host.configFileParsingResult) {
+            setConfigFileParsingResult(host.configFileParsingResult);
+            newLine = updateNewLine();
+        }
         reportWatchDiagnostic(ts.Diagnostics.Starting_compilation_in_watch_mode);
-        if (configFileName) {
+        if (configFileName && !host.configFileParsingResult) {
             newLine = ts.getNewLineCharacter(optionsToExtendForConfigFile, function () { return host.getNewLine(); });
-            if (host.configFileParsingResult) {
-                setConfigFileParsingResult(host.configFileParsingResult);
-            }
-            else {
-                ts.Debug.assert(!rootFileNames);
-                parseConfigFile();
-            }
+            ts.Debug.assert(!rootFileNames);
+            parseConfigFile();
             newLine = updateNewLine();
         }
         var trace = host.trace && (function (s) { host.trace(s + newLine); });
@@ -87200,6 +87196,7 @@ var ts;
             return builder.cleanAllProjects();
         }
         if (watch) {
+            builder.buildAllProjects();
             builder.startWatching();
             return undefined;
         }