diff --git a/lib/tsc.js b/lib/tsc.js
index 3fb71924bd1..1577f9f0c17 100644
--- a/lib/tsc.js
+++ b/lib/tsc.js
@@ -191,7 +191,17 @@ var ts;
         return undefined;
     }
     ts.forEach = forEach;
-    function find(array, callback) {
+    function find(array, predicate) {
+        for (var i = 0, len = array.length; i < len; i++) {
+            var value = array[i];
+            if (predicate(value, i)) {
+                return value;
+            }
+        }
+        return undefined;
+    }
+    ts.find = find;
+    function findMap(array, callback) {
         for (var i = 0, len = array.length; i < len; i++) {
             var result = callback(array[i], i);
             if (result) {
@@ -200,7 +210,7 @@ var ts;
         }
         Debug.fail();
     }
-    ts.find = find;
+    ts.findMap = findMap;
     function contains(array, value) {
         if (array) {
             for (var _i = 0, array_1 = array; _i < array_1.length; _i++) {
@@ -1158,6 +1168,7 @@ var ts;
     }
     ts.getScriptKindFromFileName = getScriptKindFromFileName;
     ts.supportedTypeScriptExtensions = [".ts", ".tsx", ".d.ts"];
+    ts.supportedTypescriptExtensionsForExtractExtension = [".d.ts", ".ts", ".tsx"];
     ts.supportedJavascriptExtensions = [".js", ".jsx"];
     var allSupportedExtensions = ts.supportedTypeScriptExtensions.concat(ts.supportedJavascriptExtensions);
     function getSupportedExtensions(options) {
@@ -1220,9 +1231,13 @@ var ts;
     }
     ts.removeFileExtension = removeFileExtension;
     function tryRemoveExtension(path, extension) {
-        return fileExtensionIs(path, extension) ? path.substring(0, path.length - extension.length) : undefined;
+        return fileExtensionIs(path, extension) ? removeExtension(path, extension) : undefined;
     }
     ts.tryRemoveExtension = tryRemoveExtension;
+    function removeExtension(path, extension) {
+        return path.substring(0, path.length - extension.length);
+    }
+    ts.removeExtension = removeExtension;
     function isJsxOrTsxExtension(ext) {
         return ext === ".jsx" || ext === ".tsx";
     }
@@ -2227,6 +2242,7 @@ var ts;
         Cannot_find_type_definition_file_for_0: { code: 2688, category: ts.DiagnosticCategory.Error, key: "Cannot_find_type_definition_file_for_0_2688", message: "Cannot find type definition file for '{0}'." },
         Cannot_extend_an_interface_0_Did_you_mean_implements: { code: 2689, category: ts.DiagnosticCategory.Error, key: "Cannot_extend_an_interface_0_Did_you_mean_implements_2689", message: "Cannot extend an interface '{0}'. Did you mean 'implements'?" },
         A_class_must_be_declared_after_its_base_class: { code: 2690, category: ts.DiagnosticCategory.Error, key: "A_class_must_be_declared_after_its_base_class_2690", message: "A class must be declared after its base class." },
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: { code: 2691, category: ts.DiagnosticCategory.Error, key: "An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead_2691", message: "An import path cannot end with a '{0}' extension. Consider importing '{1}' instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: ts.DiagnosticCategory.Error, key: "Import_declaration_0_is_using_private_name_1_4000", message: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_class_has_or_is_using_private_name_1_4002", message: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1_4004", message: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -6230,6 +6246,10 @@ var ts;
         return ts.forEach(ts.supportedTypeScriptExtensions, function (extension) { return ts.fileExtensionIs(fileName, extension); });
     }
     ts.hasTypeScriptFileExtension = hasTypeScriptFileExtension;
+    function tryExtractTypeScriptExtension(fileName) {
+        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
+    }
+    ts.tryExtractTypeScriptExtension = tryExtractTypeScriptExtension;
     function getExpandedCharCodes(input) {
         var output = [];
         var length = input.length;
@@ -8837,6 +8857,8 @@ var ts;
                     return parseTypeOfExpression();
                 case 103:
                     return parseVoidExpression();
+                case 119:
+                    return parseAwaitExpression();
                 case 25:
                     return parseTypeAssertion();
                 default:
@@ -13902,7 +13924,7 @@ var ts;
             }
         }
         function getDeclarationOfAliasSymbol(symbol) {
-            return ts.find(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
+            return ts.findMap(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
         }
         function getTargetOfImportEqualsDeclaration(node) {
             if (node.moduleReference.kind === 240) {
@@ -14162,7 +14184,14 @@ var ts;
                 }
             }
             if (moduleNotFoundError) {
-                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                var tsExtension = ts.tryExtractTypeScriptExtension(moduleName);
+                if (tsExtension) {
+                    var diag = ts.Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
+                    error(moduleReferenceLiteral, diag, tsExtension, ts.removeExtension(moduleName, tsExtension));
+                }
+                else {
+                    error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                }
             }
             return undefined;
         }
@@ -15526,25 +15555,23 @@ var ts;
                 return checkIdentifier(declaration.name);
             }
             if (ts.isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(declaration.name, false);
+                return getTypeFromBindingPattern(declaration.name, false, true);
             }
             return undefined;
         }
-        function getTypeFromBindingElement(element, includePatternInType) {
+        function getTypeFromBindingElement(element, includePatternInType, reportErrors) {
             if (element.initializer) {
-                var type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
-                return getWidenedType(type);
+                return checkExpressionCached(element.initializer);
             }
             if (ts.isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(element.name, includePatternInType);
+                return getTypeFromBindingPattern(element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
-        function getTypeFromObjectBindingPattern(pattern, includePatternInType) {
+        function getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors) {
             var members = ts.createMap();
             var hasComputedProperties = false;
             ts.forEach(pattern.elements, function (e) {
@@ -15556,7 +15583,7 @@ var ts;
                 var text = getTextOfPropertyName(name);
                 var flags = 4 | 67108864 | (e.initializer ? 536870912 : 0);
                 var symbol = createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -15569,12 +15596,12 @@ var ts;
             }
             return result;
         }
-        function getTypeFromArrayBindingPattern(pattern, includePatternInType) {
+        function getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors) {
             var elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= 2 ? createIterableType(anyType) : anyArrayType;
             }
-            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType); });
+            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors); });
             if (includePatternInType) {
                 var result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -15582,10 +15609,10 @@ var ts;
             }
             return createTupleType(elementTypes);
         }
-        function getTypeFromBindingPattern(pattern, includePatternInType) {
+        function getTypeFromBindingPattern(pattern, includePatternInType, reportErrors) {
             return pattern.kind === 167
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
         function getWidenedTypeForVariableLikeDeclaration(declaration, reportErrors) {
             var type = getTypeForVariableLikeDeclaration(declaration, true);
@@ -20649,7 +20676,7 @@ var ts;
                     }
                 }
                 if (ts.isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(declaration.name, true);
+                    return getTypeFromBindingPattern(declaration.name, true, false);
                 }
                 if (ts.isBindingPattern(declaration.parent)) {
                     var parentDeclaration = declaration.parent.parent;
@@ -24016,12 +24043,7 @@ var ts;
                 checkSignatureDeclaration(node);
                 if (node.kind === 149) {
                     if (!ts.isInAmbientContext(node) && ts.nodeIsPresent(node.body) && (node.flags & 32768)) {
-                        if (node.flags & 65536) {
-                            if (compilerOptions.noImplicitReturns) {
-                                error(node.name, ts.Diagnostics.Not_all_code_paths_return_a_value);
-                            }
-                        }
-                        else {
+                        if (!(node.flags & 65536)) {
                             error(node.name, ts.Diagnostics.A_get_accessor_must_return_a_value);
                         }
                     }
@@ -24043,7 +24065,10 @@ var ts;
                         checkAccessorDeclarationTypesIdentical(node, otherAccessor, getThisTypeOfDeclaration, ts.Diagnostics.get_and_set_accessor_must_have_the_same_this_type);
                     }
                 }
-                getTypeOfAccessors(getSymbolOfNode(node));
+                var returnType = getTypeOfAccessors(getSymbolOfNode(node));
+                if (node.kind === 149) {
+                    checkAllCodePathsInNonVoidFunctionReturnOrThrow(node, returnType);
+                }
             }
             if (node.parent.kind !== 171) {
                 checkSourceElement(node.body);
@@ -36934,9 +36959,9 @@ var ts;
     }
     ts.directoryProbablyExists = directoryProbablyExists;
     function loadModuleFromFile(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
-        var resolvedByAddingOrKeepingExtension = loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
-        if (resolvedByAddingOrKeepingExtension) {
-            return resolvedByAddingOrKeepingExtension;
+        var resolvedByAddingExtension = tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
+        if (resolvedByAddingExtension) {
+            return resolvedByAddingExtension;
         }
         if (ts.hasJavaScriptFileExtension(candidate)) {
             var extensionless = ts.removeFileExtension(candidate);
@@ -36944,35 +36969,33 @@ var ts;
                 var extension = candidate.substring(extensionless.length);
                 trace(state.host, ts.Diagnostics.File_name_0_has_a_1_extension_stripping_it, candidate, extension);
             }
-            return loadModuleFromFileWorker(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
+            return tryAddingExtensions(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
         }
     }
-    function loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
+    function tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
         if (!onlyRecordFailures) {
             var directory = ts.getDirectoryPath(candidate);
             if (directory) {
                 onlyRecordFailures = !directoryProbablyExists(directory, state.host);
             }
         }
-        return ts.forEach(extensions, tryLoad);
-        function tryLoad(ext) {
-            if (state.skipTsx && ts.isJsxOrTsxExtension(ext)) {
-                return undefined;
+        return ts.forEach(extensions, function (ext) {
+            return !(state.skipTsx && ts.isJsxOrTsxExtension(ext)) && tryFile(candidate + ext, failedLookupLocation, onlyRecordFailures, state);
+        });
+    }
+    function tryFile(fileName, failedLookupLocation, onlyRecordFailures, state) {
+        if (!onlyRecordFailures && state.host.fileExists(fileName)) {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
             }
-            var fileName = ts.fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
-            if (!onlyRecordFailures && state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
-                }
-                return fileName;
-            }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
-                }
-                failedLookupLocation.push(fileName);
-                return undefined;
+            return fileName;
+        }
+        else {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
             }
+            failedLookupLocation.push(fileName);
+            return undefined;
         }
     }
     function loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocation, onlyRecordFailures, state) {
@@ -36984,7 +37007,8 @@ var ts;
             }
             var typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
             if (typesFile) {
-                var result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host), state);
+                var onlyRecordFailures_1 = !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host);
+                var result = tryFile(typesFile, failedLookupLocation, onlyRecordFailures_1, state);
                 if (result) {
                     return result;
                 }
diff --git a/lib/tsserver.js b/lib/tsserver.js
index d5c4ddfe8c7..d754a623488 100644
--- a/lib/tsserver.js
+++ b/lib/tsserver.js
@@ -196,7 +196,17 @@ var ts;
         return undefined;
     }
     ts.forEach = forEach;
-    function find(array, callback) {
+    function find(array, predicate) {
+        for (var i = 0, len = array.length; i < len; i++) {
+            var value = array[i];
+            if (predicate(value, i)) {
+                return value;
+            }
+        }
+        return undefined;
+    }
+    ts.find = find;
+    function findMap(array, callback) {
         for (var i = 0, len = array.length; i < len; i++) {
             var result = callback(array[i], i);
             if (result) {
@@ -205,7 +215,7 @@ var ts;
         }
         Debug.fail();
     }
-    ts.find = find;
+    ts.findMap = findMap;
     function contains(array, value) {
         if (array) {
             for (var _i = 0, array_1 = array; _i < array_1.length; _i++) {
@@ -1163,6 +1173,7 @@ var ts;
     }
     ts.getScriptKindFromFileName = getScriptKindFromFileName;
     ts.supportedTypeScriptExtensions = [".ts", ".tsx", ".d.ts"];
+    ts.supportedTypescriptExtensionsForExtractExtension = [".d.ts", ".ts", ".tsx"];
     ts.supportedJavascriptExtensions = [".js", ".jsx"];
     var allSupportedExtensions = ts.supportedTypeScriptExtensions.concat(ts.supportedJavascriptExtensions);
     function getSupportedExtensions(options) {
@@ -1225,9 +1236,13 @@ var ts;
     }
     ts.removeFileExtension = removeFileExtension;
     function tryRemoveExtension(path, extension) {
-        return fileExtensionIs(path, extension) ? path.substring(0, path.length - extension.length) : undefined;
+        return fileExtensionIs(path, extension) ? removeExtension(path, extension) : undefined;
     }
     ts.tryRemoveExtension = tryRemoveExtension;
+    function removeExtension(path, extension) {
+        return path.substring(0, path.length - extension.length);
+    }
+    ts.removeExtension = removeExtension;
     function isJsxOrTsxExtension(ext) {
         return ext === ".jsx" || ext === ".tsx";
     }
@@ -2232,6 +2247,7 @@ var ts;
         Cannot_find_type_definition_file_for_0: { code: 2688, category: ts.DiagnosticCategory.Error, key: "Cannot_find_type_definition_file_for_0_2688", message: "Cannot find type definition file for '{0}'." },
         Cannot_extend_an_interface_0_Did_you_mean_implements: { code: 2689, category: ts.DiagnosticCategory.Error, key: "Cannot_extend_an_interface_0_Did_you_mean_implements_2689", message: "Cannot extend an interface '{0}'. Did you mean 'implements'?" },
         A_class_must_be_declared_after_its_base_class: { code: 2690, category: ts.DiagnosticCategory.Error, key: "A_class_must_be_declared_after_its_base_class_2690", message: "A class must be declared after its base class." },
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: { code: 2691, category: ts.DiagnosticCategory.Error, key: "An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead_2691", message: "An import path cannot end with a '{0}' extension. Consider importing '{1}' instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: ts.DiagnosticCategory.Error, key: "Import_declaration_0_is_using_private_name_1_4000", message: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_class_has_or_is_using_private_name_1_4002", message: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1_4004", message: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -7226,6 +7242,10 @@ var ts;
         return ts.forEach(ts.supportedTypeScriptExtensions, function (extension) { return ts.fileExtensionIs(fileName, extension); });
     }
     ts.hasTypeScriptFileExtension = hasTypeScriptFileExtension;
+    function tryExtractTypeScriptExtension(fileName) {
+        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
+    }
+    ts.tryExtractTypeScriptExtension = tryExtractTypeScriptExtension;
     function getExpandedCharCodes(input) {
         var output = [];
         var length = input.length;
@@ -9833,6 +9853,8 @@ var ts;
                     return parseTypeOfExpression();
                 case 103:
                     return parseVoidExpression();
+                case 119:
+                    return parseAwaitExpression();
                 case 25:
                     return parseTypeAssertion();
                 default:
@@ -14898,7 +14920,7 @@ var ts;
             }
         }
         function getDeclarationOfAliasSymbol(symbol) {
-            return ts.find(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
+            return ts.findMap(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
         }
         function getTargetOfImportEqualsDeclaration(node) {
             if (node.moduleReference.kind === 240) {
@@ -15158,7 +15180,14 @@ var ts;
                 }
             }
             if (moduleNotFoundError) {
-                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                var tsExtension = ts.tryExtractTypeScriptExtension(moduleName);
+                if (tsExtension) {
+                    var diag = ts.Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
+                    error(moduleReferenceLiteral, diag, tsExtension, ts.removeExtension(moduleName, tsExtension));
+                }
+                else {
+                    error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                }
             }
             return undefined;
         }
@@ -16522,25 +16551,23 @@ var ts;
                 return checkIdentifier(declaration.name);
             }
             if (ts.isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(declaration.name, false);
+                return getTypeFromBindingPattern(declaration.name, false, true);
             }
             return undefined;
         }
-        function getTypeFromBindingElement(element, includePatternInType) {
+        function getTypeFromBindingElement(element, includePatternInType, reportErrors) {
             if (element.initializer) {
-                var type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
-                return getWidenedType(type);
+                return checkExpressionCached(element.initializer);
             }
             if (ts.isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(element.name, includePatternInType);
+                return getTypeFromBindingPattern(element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
-        function getTypeFromObjectBindingPattern(pattern, includePatternInType) {
+        function getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors) {
             var members = ts.createMap();
             var hasComputedProperties = false;
             ts.forEach(pattern.elements, function (e) {
@@ -16552,7 +16579,7 @@ var ts;
                 var text = getTextOfPropertyName(name);
                 var flags = 4 | 67108864 | (e.initializer ? 536870912 : 0);
                 var symbol = createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -16565,12 +16592,12 @@ var ts;
             }
             return result;
         }
-        function getTypeFromArrayBindingPattern(pattern, includePatternInType) {
+        function getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors) {
             var elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= 2 ? createIterableType(anyType) : anyArrayType;
             }
-            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType); });
+            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors); });
             if (includePatternInType) {
                 var result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -16578,10 +16605,10 @@ var ts;
             }
             return createTupleType(elementTypes);
         }
-        function getTypeFromBindingPattern(pattern, includePatternInType) {
+        function getTypeFromBindingPattern(pattern, includePatternInType, reportErrors) {
             return pattern.kind === 167
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
         function getWidenedTypeForVariableLikeDeclaration(declaration, reportErrors) {
             var type = getTypeForVariableLikeDeclaration(declaration, true);
@@ -21645,7 +21672,7 @@ var ts;
                     }
                 }
                 if (ts.isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(declaration.name, true);
+                    return getTypeFromBindingPattern(declaration.name, true, false);
                 }
                 if (ts.isBindingPattern(declaration.parent)) {
                     var parentDeclaration = declaration.parent.parent;
@@ -25012,12 +25039,7 @@ var ts;
                 checkSignatureDeclaration(node);
                 if (node.kind === 149) {
                     if (!ts.isInAmbientContext(node) && ts.nodeIsPresent(node.body) && (node.flags & 32768)) {
-                        if (node.flags & 65536) {
-                            if (compilerOptions.noImplicitReturns) {
-                                error(node.name, ts.Diagnostics.Not_all_code_paths_return_a_value);
-                            }
-                        }
-                        else {
+                        if (!(node.flags & 65536)) {
                             error(node.name, ts.Diagnostics.A_get_accessor_must_return_a_value);
                         }
                     }
@@ -25039,7 +25061,10 @@ var ts;
                         checkAccessorDeclarationTypesIdentical(node, otherAccessor, getThisTypeOfDeclaration, ts.Diagnostics.get_and_set_accessor_must_have_the_same_this_type);
                     }
                 }
-                getTypeOfAccessors(getSymbolOfNode(node));
+                var returnType = getTypeOfAccessors(getSymbolOfNode(node));
+                if (node.kind === 149) {
+                    checkAllCodePathsInNonVoidFunctionReturnOrThrow(node, returnType);
+                }
             }
             if (node.parent.kind !== 171) {
                 checkSourceElement(node.body);
@@ -37930,9 +37955,9 @@ var ts;
     }
     ts.directoryProbablyExists = directoryProbablyExists;
     function loadModuleFromFile(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
-        var resolvedByAddingOrKeepingExtension = loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
-        if (resolvedByAddingOrKeepingExtension) {
-            return resolvedByAddingOrKeepingExtension;
+        var resolvedByAddingExtension = tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
+        if (resolvedByAddingExtension) {
+            return resolvedByAddingExtension;
         }
         if (ts.hasJavaScriptFileExtension(candidate)) {
             var extensionless = ts.removeFileExtension(candidate);
@@ -37940,35 +37965,33 @@ var ts;
                 var extension = candidate.substring(extensionless.length);
                 trace(state.host, ts.Diagnostics.File_name_0_has_a_1_extension_stripping_it, candidate, extension);
             }
-            return loadModuleFromFileWorker(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
+            return tryAddingExtensions(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
         }
     }
-    function loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
+    function tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
         if (!onlyRecordFailures) {
             var directory = ts.getDirectoryPath(candidate);
             if (directory) {
                 onlyRecordFailures = !directoryProbablyExists(directory, state.host);
             }
         }
-        return ts.forEach(extensions, tryLoad);
-        function tryLoad(ext) {
-            if (state.skipTsx && ts.isJsxOrTsxExtension(ext)) {
-                return undefined;
+        return ts.forEach(extensions, function (ext) {
+            return !(state.skipTsx && ts.isJsxOrTsxExtension(ext)) && tryFile(candidate + ext, failedLookupLocation, onlyRecordFailures, state);
+        });
+    }
+    function tryFile(fileName, failedLookupLocation, onlyRecordFailures, state) {
+        if (!onlyRecordFailures && state.host.fileExists(fileName)) {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
             }
-            var fileName = ts.fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
-            if (!onlyRecordFailures && state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
-                }
-                return fileName;
-            }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
-                }
-                failedLookupLocation.push(fileName);
-                return undefined;
+            return fileName;
+        }
+        else {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
             }
+            failedLookupLocation.push(fileName);
+            return undefined;
         }
     }
     function loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocation, onlyRecordFailures, state) {
@@ -37980,7 +38003,8 @@ var ts;
             }
             var typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
             if (typesFile) {
-                var result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host), state);
+                var onlyRecordFailures_1 = !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host);
+                var result = tryFile(typesFile, failedLookupLocation, onlyRecordFailures_1, state);
                 if (result) {
                     return result;
                 }
@@ -47669,6 +47693,24 @@ var ts;
             }
             if (!documentation) {
                 documentation = symbol.getDocumentationComment();
+                if (documentation.length === 0 && symbol.flags & 4) {
+                    if (symbol.parent && ts.forEach(symbol.parent.declarations, function (declaration) { return declaration.kind === 256; })) {
+                        for (var _i = 0, _a = symbol.declarations; _i < _a.length; _i++) {
+                            var declaration = _a[_i];
+                            if (!declaration.parent || declaration.parent.kind !== 187) {
+                                continue;
+                            }
+                            var rhsSymbol = program.getTypeChecker().getSymbolAtLocation(declaration.parent.right);
+                            if (!rhsSymbol) {
+                                continue;
+                            }
+                            documentation = rhsSymbol.getDocumentationComment();
+                            if (documentation.length > 0) {
+                                break;
+                            }
+                        }
+                    }
+                }
             }
             return { displayParts: displayParts, documentation: documentation, symbolKind: symbolKind };
             function addNewLineIfDisplayPartsExist() {
diff --git a/lib/tsserverlibrary.d.ts b/lib/tsserverlibrary.d.ts
index 16d187657f0..5c7096df482 100644
--- a/lib/tsserverlibrary.d.ts
+++ b/lib/tsserverlibrary.d.ts
@@ -2150,7 +2150,8 @@ declare namespace ts {
         GreaterThan = 1,
     }
     function forEach<T, U>(array: T[] | undefined, callback: (element: T, index: number) => U | undefined): U | undefined;
-    function find<T, U>(array: T[], callback: (element: T, index: number) => U | undefined): U;
+    function find<T>(array: T[], predicate: (element: T, index: number) => boolean): T | undefined;
+    function findMap<T, U>(array: T[], callback: (element: T, index: number) => U | undefined): U;
     function contains<T>(array: T[], value: T): boolean;
     function indexOf<T>(array: T[], value: T): number;
     function indexOfAnyCharCode(text: string, charCodes: number[], start?: number): number;
@@ -2237,6 +2238,7 @@ declare namespace ts {
     function ensureScriptKind(fileName: string, scriptKind?: ScriptKind): ScriptKind;
     function getScriptKindFromFileName(fileName: string): ScriptKind;
     const supportedTypeScriptExtensions: string[];
+    const supportedTypescriptExtensionsForExtractExtension: string[];
     const supportedJavascriptExtensions: string[];
     function getSupportedExtensions(options?: CompilerOptions): string[];
     function isSupportedSourceFileName(fileName: string, compilerOptions?: CompilerOptions): boolean;
@@ -2251,7 +2253,8 @@ declare namespace ts {
     function adjustExtensionPriority(extensionPriority: ExtensionPriority): ExtensionPriority;
     function getNextLowestExtensionPriority(extensionPriority: ExtensionPriority): ExtensionPriority;
     function removeFileExtension(path: string): string;
-    function tryRemoveExtension(path: string, extension: string): string;
+    function tryRemoveExtension(path: string, extension: string): string | undefined;
+    function removeExtension(path: string, extension: string): string;
     function isJsxOrTsxExtension(ext: string): boolean;
     function changeExtension<T extends string | Path>(path: T, newExtension: string): T;
     interface ObjectAllocator {
@@ -5249,6 +5252,12 @@ declare namespace ts {
             key: string;
             message: string;
         };
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: {
+            code: number;
+            category: DiagnosticCategory;
+            key: string;
+            message: string;
+        };
         Import_declaration_0_is_using_private_name_1: {
             code: number;
             category: DiagnosticCategory;
@@ -7208,6 +7217,7 @@ declare namespace ts {
     function getLocalSymbolForExportDefault(symbol: Symbol): Symbol;
     function hasJavaScriptFileExtension(fileName: string): boolean;
     function hasTypeScriptFileExtension(fileName: string): boolean;
+    function tryExtractTypeScriptExtension(fileName: string): string | undefined;
     const stringify: (value: any) => string;
     function convertToBase64(input: string): string;
     function convertToRelativePath(absoluteOrRelativePath: string, basePath: string, getCanonicalFileName: (path: string) => string): string;
diff --git a/lib/tsserverlibrary.js b/lib/tsserverlibrary.js
index 9a1ae13d058..a7fb4b6b2f8 100644
--- a/lib/tsserverlibrary.js
+++ b/lib/tsserverlibrary.js
@@ -196,7 +196,17 @@ var ts;
         return undefined;
     }
     ts.forEach = forEach;
-    function find(array, callback) {
+    function find(array, predicate) {
+        for (var i = 0, len = array.length; i < len; i++) {
+            var value = array[i];
+            if (predicate(value, i)) {
+                return value;
+            }
+        }
+        return undefined;
+    }
+    ts.find = find;
+    function findMap(array, callback) {
         for (var i = 0, len = array.length; i < len; i++) {
             var result = callback(array[i], i);
             if (result) {
@@ -205,7 +215,7 @@ var ts;
         }
         Debug.fail();
     }
-    ts.find = find;
+    ts.findMap = findMap;
     function contains(array, value) {
         if (array) {
             for (var _i = 0, array_1 = array; _i < array_1.length; _i++) {
@@ -1163,6 +1173,7 @@ var ts;
     }
     ts.getScriptKindFromFileName = getScriptKindFromFileName;
     ts.supportedTypeScriptExtensions = [".ts", ".tsx", ".d.ts"];
+    ts.supportedTypescriptExtensionsForExtractExtension = [".d.ts", ".ts", ".tsx"];
     ts.supportedJavascriptExtensions = [".js", ".jsx"];
     var allSupportedExtensions = ts.supportedTypeScriptExtensions.concat(ts.supportedJavascriptExtensions);
     function getSupportedExtensions(options) {
@@ -1225,9 +1236,13 @@ var ts;
     }
     ts.removeFileExtension = removeFileExtension;
     function tryRemoveExtension(path, extension) {
-        return fileExtensionIs(path, extension) ? path.substring(0, path.length - extension.length) : undefined;
+        return fileExtensionIs(path, extension) ? removeExtension(path, extension) : undefined;
     }
     ts.tryRemoveExtension = tryRemoveExtension;
+    function removeExtension(path, extension) {
+        return path.substring(0, path.length - extension.length);
+    }
+    ts.removeExtension = removeExtension;
     function isJsxOrTsxExtension(ext) {
         return ext === ".jsx" || ext === ".tsx";
     }
@@ -2232,6 +2247,7 @@ var ts;
         Cannot_find_type_definition_file_for_0: { code: 2688, category: ts.DiagnosticCategory.Error, key: "Cannot_find_type_definition_file_for_0_2688", message: "Cannot find type definition file for '{0}'." },
         Cannot_extend_an_interface_0_Did_you_mean_implements: { code: 2689, category: ts.DiagnosticCategory.Error, key: "Cannot_extend_an_interface_0_Did_you_mean_implements_2689", message: "Cannot extend an interface '{0}'. Did you mean 'implements'?" },
         A_class_must_be_declared_after_its_base_class: { code: 2690, category: ts.DiagnosticCategory.Error, key: "A_class_must_be_declared_after_its_base_class_2690", message: "A class must be declared after its base class." },
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: { code: 2691, category: ts.DiagnosticCategory.Error, key: "An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead_2691", message: "An import path cannot end with a '{0}' extension. Consider importing '{1}' instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: ts.DiagnosticCategory.Error, key: "Import_declaration_0_is_using_private_name_1_4000", message: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_class_has_or_is_using_private_name_1_4002", message: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1_4004", message: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -7226,6 +7242,10 @@ var ts;
         return ts.forEach(ts.supportedTypeScriptExtensions, function (extension) { return ts.fileExtensionIs(fileName, extension); });
     }
     ts.hasTypeScriptFileExtension = hasTypeScriptFileExtension;
+    function tryExtractTypeScriptExtension(fileName) {
+        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
+    }
+    ts.tryExtractTypeScriptExtension = tryExtractTypeScriptExtension;
     function getExpandedCharCodes(input) {
         var output = [];
         var length = input.length;
@@ -9833,6 +9853,8 @@ var ts;
                     return parseTypeOfExpression();
                 case 103:
                     return parseVoidExpression();
+                case 119:
+                    return parseAwaitExpression();
                 case 25:
                     return parseTypeAssertion();
                 default:
@@ -14898,7 +14920,7 @@ var ts;
             }
         }
         function getDeclarationOfAliasSymbol(symbol) {
-            return ts.find(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
+            return ts.findMap(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
         }
         function getTargetOfImportEqualsDeclaration(node) {
             if (node.moduleReference.kind === 240) {
@@ -15158,7 +15180,14 @@ var ts;
                 }
             }
             if (moduleNotFoundError) {
-                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                var tsExtension = ts.tryExtractTypeScriptExtension(moduleName);
+                if (tsExtension) {
+                    var diag = ts.Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
+                    error(moduleReferenceLiteral, diag, tsExtension, ts.removeExtension(moduleName, tsExtension));
+                }
+                else {
+                    error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                }
             }
             return undefined;
         }
@@ -16522,25 +16551,23 @@ var ts;
                 return checkIdentifier(declaration.name);
             }
             if (ts.isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(declaration.name, false);
+                return getTypeFromBindingPattern(declaration.name, false, true);
             }
             return undefined;
         }
-        function getTypeFromBindingElement(element, includePatternInType) {
+        function getTypeFromBindingElement(element, includePatternInType, reportErrors) {
             if (element.initializer) {
-                var type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
-                return getWidenedType(type);
+                return checkExpressionCached(element.initializer);
             }
             if (ts.isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(element.name, includePatternInType);
+                return getTypeFromBindingPattern(element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
-        function getTypeFromObjectBindingPattern(pattern, includePatternInType) {
+        function getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors) {
             var members = ts.createMap();
             var hasComputedProperties = false;
             ts.forEach(pattern.elements, function (e) {
@@ -16552,7 +16579,7 @@ var ts;
                 var text = getTextOfPropertyName(name);
                 var flags = 4 | 67108864 | (e.initializer ? 536870912 : 0);
                 var symbol = createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -16565,12 +16592,12 @@ var ts;
             }
             return result;
         }
-        function getTypeFromArrayBindingPattern(pattern, includePatternInType) {
+        function getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors) {
             var elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= 2 ? createIterableType(anyType) : anyArrayType;
             }
-            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType); });
+            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors); });
             if (includePatternInType) {
                 var result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -16578,10 +16605,10 @@ var ts;
             }
             return createTupleType(elementTypes);
         }
-        function getTypeFromBindingPattern(pattern, includePatternInType) {
+        function getTypeFromBindingPattern(pattern, includePatternInType, reportErrors) {
             return pattern.kind === 167
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
         function getWidenedTypeForVariableLikeDeclaration(declaration, reportErrors) {
             var type = getTypeForVariableLikeDeclaration(declaration, true);
@@ -21645,7 +21672,7 @@ var ts;
                     }
                 }
                 if (ts.isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(declaration.name, true);
+                    return getTypeFromBindingPattern(declaration.name, true, false);
                 }
                 if (ts.isBindingPattern(declaration.parent)) {
                     var parentDeclaration = declaration.parent.parent;
@@ -25012,12 +25039,7 @@ var ts;
                 checkSignatureDeclaration(node);
                 if (node.kind === 149) {
                     if (!ts.isInAmbientContext(node) && ts.nodeIsPresent(node.body) && (node.flags & 32768)) {
-                        if (node.flags & 65536) {
-                            if (compilerOptions.noImplicitReturns) {
-                                error(node.name, ts.Diagnostics.Not_all_code_paths_return_a_value);
-                            }
-                        }
-                        else {
+                        if (!(node.flags & 65536)) {
                             error(node.name, ts.Diagnostics.A_get_accessor_must_return_a_value);
                         }
                     }
@@ -25039,7 +25061,10 @@ var ts;
                         checkAccessorDeclarationTypesIdentical(node, otherAccessor, getThisTypeOfDeclaration, ts.Diagnostics.get_and_set_accessor_must_have_the_same_this_type);
                     }
                 }
-                getTypeOfAccessors(getSymbolOfNode(node));
+                var returnType = getTypeOfAccessors(getSymbolOfNode(node));
+                if (node.kind === 149) {
+                    checkAllCodePathsInNonVoidFunctionReturnOrThrow(node, returnType);
+                }
             }
             if (node.parent.kind !== 171) {
                 checkSourceElement(node.body);
@@ -37930,9 +37955,9 @@ var ts;
     }
     ts.directoryProbablyExists = directoryProbablyExists;
     function loadModuleFromFile(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
-        var resolvedByAddingOrKeepingExtension = loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
-        if (resolvedByAddingOrKeepingExtension) {
-            return resolvedByAddingOrKeepingExtension;
+        var resolvedByAddingExtension = tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
+        if (resolvedByAddingExtension) {
+            return resolvedByAddingExtension;
         }
         if (ts.hasJavaScriptFileExtension(candidate)) {
             var extensionless = ts.removeFileExtension(candidate);
@@ -37940,35 +37965,33 @@ var ts;
                 var extension = candidate.substring(extensionless.length);
                 trace(state.host, ts.Diagnostics.File_name_0_has_a_1_extension_stripping_it, candidate, extension);
             }
-            return loadModuleFromFileWorker(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
+            return tryAddingExtensions(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
         }
     }
-    function loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
+    function tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
         if (!onlyRecordFailures) {
             var directory = ts.getDirectoryPath(candidate);
             if (directory) {
                 onlyRecordFailures = !directoryProbablyExists(directory, state.host);
             }
         }
-        return ts.forEach(extensions, tryLoad);
-        function tryLoad(ext) {
-            if (state.skipTsx && ts.isJsxOrTsxExtension(ext)) {
-                return undefined;
+        return ts.forEach(extensions, function (ext) {
+            return !(state.skipTsx && ts.isJsxOrTsxExtension(ext)) && tryFile(candidate + ext, failedLookupLocation, onlyRecordFailures, state);
+        });
+    }
+    function tryFile(fileName, failedLookupLocation, onlyRecordFailures, state) {
+        if (!onlyRecordFailures && state.host.fileExists(fileName)) {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
             }
-            var fileName = ts.fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
-            if (!onlyRecordFailures && state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
-                }
-                return fileName;
-            }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
-                }
-                failedLookupLocation.push(fileName);
-                return undefined;
+            return fileName;
+        }
+        else {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
             }
+            failedLookupLocation.push(fileName);
+            return undefined;
         }
     }
     function loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocation, onlyRecordFailures, state) {
@@ -37980,7 +38003,8 @@ var ts;
             }
             var typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
             if (typesFile) {
-                var result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host), state);
+                var onlyRecordFailures_1 = !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host);
+                var result = tryFile(typesFile, failedLookupLocation, onlyRecordFailures_1, state);
                 if (result) {
                     return result;
                 }
@@ -47669,6 +47693,24 @@ var ts;
             }
             if (!documentation) {
                 documentation = symbol.getDocumentationComment();
+                if (documentation.length === 0 && symbol.flags & 4) {
+                    if (symbol.parent && ts.forEach(symbol.parent.declarations, function (declaration) { return declaration.kind === 256; })) {
+                        for (var _i = 0, _a = symbol.declarations; _i < _a.length; _i++) {
+                            var declaration = _a[_i];
+                            if (!declaration.parent || declaration.parent.kind !== 187) {
+                                continue;
+                            }
+                            var rhsSymbol = program.getTypeChecker().getSymbolAtLocation(declaration.parent.right);
+                            if (!rhsSymbol) {
+                                continue;
+                            }
+                            documentation = rhsSymbol.getDocumentationComment();
+                            if (documentation.length > 0) {
+                                break;
+                            }
+                        }
+                    }
+                }
             }
             return { displayParts: displayParts, documentation: documentation, symbolKind: symbolKind };
             function addNewLineIfDisplayPartsExist() {
diff --git a/lib/typescript.js b/lib/typescript.js
index 2af3c3b4efd..3e7cc3d90ca 100644
--- a/lib/typescript.js
+++ b/lib/typescript.js
@@ -1103,8 +1103,22 @@ var ts;
         return undefined;
     }
     ts.forEach = forEach;
-    /** Like `forEach`, but assumes existence of array and fails if no truthy value is found. */
-    function find(array, callback) {
+    /** Works like Array.prototype.find, returning `undefined` if no element satisfying the predicate is found. */
+    function find(array, predicate) {
+        for (var i = 0, len = array.length; i < len; i++) {
+            var value = array[i];
+            if (predicate(value, i)) {
+                return value;
+            }
+        }
+        return undefined;
+    }
+    ts.find = find;
+    /**
+     * Returns the first truthy result of `callback`, or else fails.
+     * This is like `forEach`, but never returns undefined.
+     */
+    function findMap(array, callback) {
         for (var i = 0, len = array.length; i < len; i++) {
             var result = callback(array[i], i);
             if (result) {
@@ -1113,7 +1127,7 @@ var ts;
         }
         Debug.fail();
     }
-    ts.find = find;
+    ts.findMap = findMap;
     function contains(array, value) {
         if (array) {
             for (var _i = 0, array_1 = array; _i < array_1.length; _i++) {
@@ -2239,6 +2253,8 @@ var ts;
      *  List of supported extensions in order of file resolution precedence.
      */
     ts.supportedTypeScriptExtensions = [".ts", ".tsx", ".d.ts"];
+    /** Must have ".d.ts" first because if ".ts" goes first, that will be detected as the extension instead of ".d.ts". */
+    ts.supportedTypescriptExtensionsForExtractExtension = [".d.ts", ".ts", ".tsx"];
     ts.supportedJavascriptExtensions = [".js", ".jsx"];
     var allSupportedExtensions = ts.supportedTypeScriptExtensions.concat(ts.supportedJavascriptExtensions);
     function getSupportedExtensions(options) {
@@ -2322,9 +2338,13 @@ var ts;
     }
     ts.removeFileExtension = removeFileExtension;
     function tryRemoveExtension(path, extension) {
-        return fileExtensionIs(path, extension) ? path.substring(0, path.length - extension.length) : undefined;
+        return fileExtensionIs(path, extension) ? removeExtension(path, extension) : undefined;
     }
     ts.tryRemoveExtension = tryRemoveExtension;
+    function removeExtension(path, extension) {
+        return path.substring(0, path.length - extension.length);
+    }
+    ts.removeExtension = removeExtension;
     function isJsxOrTsxExtension(ext) {
         return ext === ".jsx" || ext === ".tsx";
     }
@@ -3374,6 +3394,7 @@ var ts;
         Cannot_find_type_definition_file_for_0: { code: 2688, category: ts.DiagnosticCategory.Error, key: "Cannot_find_type_definition_file_for_0_2688", message: "Cannot find type definition file for '{0}'." },
         Cannot_extend_an_interface_0_Did_you_mean_implements: { code: 2689, category: ts.DiagnosticCategory.Error, key: "Cannot_extend_an_interface_0_Did_you_mean_implements_2689", message: "Cannot extend an interface '{0}'. Did you mean 'implements'?" },
         A_class_must_be_declared_after_its_base_class: { code: 2690, category: ts.DiagnosticCategory.Error, key: "A_class_must_be_declared_after_its_base_class_2690", message: "A class must be declared after its base class." },
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: { code: 2691, category: ts.DiagnosticCategory.Error, key: "An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead_2691", message: "An import path cannot end with a '{0}' extension. Consider importing '{1}' instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: ts.DiagnosticCategory.Error, key: "Import_declaration_0_is_using_private_name_1_4000", message: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_class_has_or_is_using_private_name_1_4002", message: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1_4004", message: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -7813,6 +7834,11 @@ var ts;
         return ts.forEach(ts.supportedTypeScriptExtensions, function (extension) { return ts.fileExtensionIs(fileName, extension); });
     }
     ts.hasTypeScriptFileExtension = hasTypeScriptFileExtension;
+    /** Return ".ts", ".d.ts", or ".tsx", if that is the extension. */
+    function tryExtractTypeScriptExtension(fileName) {
+        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
+    }
+    ts.tryExtractTypeScriptExtension = tryExtractTypeScriptExtension;
     /**
      * Replace each instance of non-ascii characters by one, two, three, or four escape sequences
      * representing the UTF-8 encoding of the character, and return the expanded char code list.
@@ -11188,6 +11214,7 @@ var ts;
          *      6) - UnaryExpression[?yield]
          *      7) ~ UnaryExpression[?yield]
          *      8) ! UnaryExpression[?yield]
+         *      9) [+Await] await UnaryExpression[?yield]
          */
         function parseSimpleUnaryExpression() {
             switch (token()) {
@@ -11202,6 +11229,8 @@ var ts;
                     return parseTypeOfExpression();
                 case 103 /* VoidKeyword */:
                     return parseVoidExpression();
+                case 119 /* AwaitKeyword */:
+                    return parseAwaitExpression();
                 case 25 /* LessThanToken */:
                     // This is modified UnaryExpression grammar in TypeScript
                     //  UnaryExpression (modified):
@@ -17373,7 +17402,7 @@ var ts;
             }
         }
         function getDeclarationOfAliasSymbol(symbol) {
-            return ts.find(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
+            return ts.findMap(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
         }
         function getTargetOfImportEqualsDeclaration(node) {
             if (node.moduleReference.kind === 240 /* ExternalModuleReference */) {
@@ -17677,7 +17706,14 @@ var ts;
             }
             if (moduleNotFoundError) {
                 // report errors only if it was requested
-                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                var tsExtension = ts.tryExtractTypeScriptExtension(moduleName);
+                if (tsExtension) {
+                    var diag = ts.Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
+                    error(moduleReferenceLiteral, diag, tsExtension, ts.removeExtension(moduleName, tsExtension));
+                }
+                else {
+                    error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                }
             }
             return undefined;
         }
@@ -19227,7 +19263,7 @@ var ts;
             }
             // If the declaration specifies a binding pattern, use the type implied by the binding pattern
             if (ts.isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ false);
+                return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ false, /*reportErrors*/ true);
             }
             // No type specified and nothing can be inferred
             return undefined;
@@ -19235,22 +19271,20 @@ var ts;
         // Return the type implied by a binding pattern element. This is the type of the initializer of the element if
         // one is present. Otherwise, if the element is itself a binding pattern, it is the type implied by the binding
         // pattern. Otherwise, it is the type any.
-        function getTypeFromBindingElement(element, includePatternInType) {
+        function getTypeFromBindingElement(element, includePatternInType, reportErrors) {
             if (element.initializer) {
-                var type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
-                return getWidenedType(type);
+                return checkExpressionCached(element.initializer);
             }
             if (ts.isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(element.name, includePatternInType);
+                return getTypeFromBindingPattern(element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
         // Return the type implied by an object binding pattern
-        function getTypeFromObjectBindingPattern(pattern, includePatternInType) {
+        function getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors) {
             var members = ts.createMap();
             var hasComputedProperties = false;
             ts.forEach(pattern.elements, function (e) {
@@ -19263,7 +19297,7 @@ var ts;
                 var text = getTextOfPropertyName(name);
                 var flags = 4 /* Property */ | 67108864 /* Transient */ | (e.initializer ? 536870912 /* Optional */ : 0);
                 var symbol = createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -19277,13 +19311,13 @@ var ts;
             return result;
         }
         // Return the type implied by an array binding pattern
-        function getTypeFromArrayBindingPattern(pattern, includePatternInType) {
+        function getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors) {
             var elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= 2 /* ES6 */ ? createIterableType(anyType) : anyArrayType;
             }
             // If the pattern has at least one element, and no rest element, then it should imply a tuple type.
-            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 /* OmittedExpression */ ? anyType : getTypeFromBindingElement(e, includePatternInType); });
+            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 /* OmittedExpression */ ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors); });
             if (includePatternInType) {
                 var result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -19298,10 +19332,10 @@ var ts;
         // used as the contextual type of an initializer associated with the binding pattern. Also, for a destructuring
         // parameter with no type annotation or initializer, the type implied by the binding pattern becomes the type of
         // the parameter.
-        function getTypeFromBindingPattern(pattern, includePatternInType) {
+        function getTypeFromBindingPattern(pattern, includePatternInType, reportErrors) {
             return pattern.kind === 167 /* ObjectBindingPattern */
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
         // Return the type associated with a variable, parameter, or property declaration. In the simple case this is the type
         // specified in a type annotation or inferred from an initializer. However, in the case of a destructuring declaration it
@@ -25069,7 +25103,7 @@ var ts;
                     }
                 }
                 if (ts.isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true);
+                    return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
                 }
                 if (ts.isBindingPattern(declaration.parent)) {
                     var parentDeclaration = declaration.parent.parent;
@@ -29299,12 +29333,7 @@ var ts;
                 checkSignatureDeclaration(node);
                 if (node.kind === 149 /* GetAccessor */) {
                     if (!ts.isInAmbientContext(node) && ts.nodeIsPresent(node.body) && (node.flags & 32768 /* HasImplicitReturn */)) {
-                        if (node.flags & 65536 /* HasExplicitReturn */) {
-                            if (compilerOptions.noImplicitReturns) {
-                                error(node.name, ts.Diagnostics.Not_all_code_paths_return_a_value);
-                            }
-                        }
-                        else {
+                        if (!(node.flags & 65536 /* HasExplicitReturn */)) {
                             error(node.name, ts.Diagnostics.A_get_accessor_must_return_a_value);
                         }
                     }
@@ -29333,7 +29362,10 @@ var ts;
                         checkAccessorDeclarationTypesIdentical(node, otherAccessor, getThisTypeOfDeclaration, ts.Diagnostics.get_and_set_accessor_must_have_the_same_this_type);
                     }
                 }
-                getTypeOfAccessors(getSymbolOfNode(node));
+                var returnType = getTypeOfAccessors(getSymbolOfNode(node));
+                if (node.kind === 149 /* GetAccessor */) {
+                    checkAllCodePathsInNonVoidFunctionReturnOrThrow(node, returnType);
+                }
             }
             if (node.parent.kind !== 171 /* ObjectLiteralExpression */) {
                 checkSourceElement(node.body);
@@ -44413,22 +44445,24 @@ var ts;
      * in cases when we know upfront that all load attempts will fail (because containing folder does not exists) however we still need to record all failed lookup locations.
      */
     function loadModuleFromFile(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
-        // First try to keep/add an extension: importing "./foo.ts" can be matched by a file "./foo.ts", and "./foo" by "./foo.d.ts"
-        var resolvedByAddingOrKeepingExtension = loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
-        if (resolvedByAddingOrKeepingExtension) {
-            return resolvedByAddingOrKeepingExtension;
+        // First, try adding an extension. An import of "foo" could be matched by a file "foo.ts", or "foo.js" by "foo.js.ts"
+        var resolvedByAddingExtension = tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
+        if (resolvedByAddingExtension) {
+            return resolvedByAddingExtension;
         }
-        // Then try stripping a ".js" or ".jsx" extension and replacing it with a TypeScript one, e.g. "./foo.js" can be matched by "./foo.ts" or "./foo.d.ts"
+        // If that didn't work, try stripping a ".js" or ".jsx" extension and replacing it with a TypeScript one;
+        // e.g. "./foo.js" can be matched by "./foo.ts" or "./foo.d.ts"
         if (ts.hasJavaScriptFileExtension(candidate)) {
             var extensionless = ts.removeFileExtension(candidate);
             if (state.traceEnabled) {
                 var extension = candidate.substring(extensionless.length);
                 trace(state.host, ts.Diagnostics.File_name_0_has_a_1_extension_stripping_it, candidate, extension);
             }
-            return loadModuleFromFileWorker(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
+            return tryAddingExtensions(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
         }
     }
-    function loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
+    /** Try to return an existing file that adds one of the `extensions` to `candidate`. */
+    function tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
         if (!onlyRecordFailures) {
             // check if containing folder exists - if it doesn't then just record failures for all supported extensions without disk probing
             var directory = ts.getDirectoryPath(candidate);
@@ -44436,25 +44470,24 @@ var ts;
                 onlyRecordFailures = !directoryProbablyExists(directory, state.host);
             }
         }
-        return ts.forEach(extensions, tryLoad);
-        function tryLoad(ext) {
-            if (state.skipTsx && ts.isJsxOrTsxExtension(ext)) {
-                return undefined;
+        return ts.forEach(extensions, function (ext) {
+            return !(state.skipTsx && ts.isJsxOrTsxExtension(ext)) && tryFile(candidate + ext, failedLookupLocation, onlyRecordFailures, state);
+        });
+    }
+    /** Return the file if it exists. */
+    function tryFile(fileName, failedLookupLocation, onlyRecordFailures, state) {
+        if (!onlyRecordFailures && state.host.fileExists(fileName)) {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
             }
-            var fileName = ts.fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
-            if (!onlyRecordFailures && state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
-                }
-                return fileName;
-            }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
-                }
-                failedLookupLocation.push(fileName);
-                return undefined;
+            return fileName;
+        }
+        else {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
             }
+            failedLookupLocation.push(fileName);
+            return undefined;
         }
     }
     function loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocation, onlyRecordFailures, state) {
@@ -44466,7 +44499,9 @@ var ts;
             }
             var typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
             if (typesFile) {
-                var result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host), state);
+                var onlyRecordFailures_1 = !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host);
+                // The package.json "typings" property must specify the file with extension, so just try that exact filename.
+                var result = tryFile(typesFile, failedLookupLocation, onlyRecordFailures_1, state);
                 if (result) {
                     return result;
                 }
@@ -56673,6 +56708,27 @@ var ts;
             }
             if (!documentation) {
                 documentation = symbol.getDocumentationComment();
+                if (documentation.length === 0 && symbol.flags & 4 /* Property */) {
+                    // For some special property access expressions like `experts.foo = foo` or `module.exports.foo = foo`
+                    // there documentation comments might be attached to the right hand side symbol of their declarations.
+                    // The pattern of such special property access is that the parent symbol is the symbol of the file.
+                    if (symbol.parent && ts.forEach(symbol.parent.declarations, function (declaration) { return declaration.kind === 256 /* SourceFile */; })) {
+                        for (var _i = 0, _a = symbol.declarations; _i < _a.length; _i++) {
+                            var declaration = _a[_i];
+                            if (!declaration.parent || declaration.parent.kind !== 187 /* BinaryExpression */) {
+                                continue;
+                            }
+                            var rhsSymbol = program.getTypeChecker().getSymbolAtLocation(declaration.parent.right);
+                            if (!rhsSymbol) {
+                                continue;
+                            }
+                            documentation = rhsSymbol.getDocumentationComment();
+                            if (documentation.length > 0) {
+                                break;
+                            }
+                        }
+                    }
+                }
             }
             return { displayParts: displayParts, documentation: documentation, symbolKind: symbolKind };
             function addNewLineIfDisplayPartsExist() {
diff --git a/lib/typescriptServices.js b/lib/typescriptServices.js
index 2af3c3b4efd..3e7cc3d90ca 100644
--- a/lib/typescriptServices.js
+++ b/lib/typescriptServices.js
@@ -1103,8 +1103,22 @@ var ts;
         return undefined;
     }
     ts.forEach = forEach;
-    /** Like `forEach`, but assumes existence of array and fails if no truthy value is found. */
-    function find(array, callback) {
+    /** Works like Array.prototype.find, returning `undefined` if no element satisfying the predicate is found. */
+    function find(array, predicate) {
+        for (var i = 0, len = array.length; i < len; i++) {
+            var value = array[i];
+            if (predicate(value, i)) {
+                return value;
+            }
+        }
+        return undefined;
+    }
+    ts.find = find;
+    /**
+     * Returns the first truthy result of `callback`, or else fails.
+     * This is like `forEach`, but never returns undefined.
+     */
+    function findMap(array, callback) {
         for (var i = 0, len = array.length; i < len; i++) {
             var result = callback(array[i], i);
             if (result) {
@@ -1113,7 +1127,7 @@ var ts;
         }
         Debug.fail();
     }
-    ts.find = find;
+    ts.findMap = findMap;
     function contains(array, value) {
         if (array) {
             for (var _i = 0, array_1 = array; _i < array_1.length; _i++) {
@@ -2239,6 +2253,8 @@ var ts;
      *  List of supported extensions in order of file resolution precedence.
      */
     ts.supportedTypeScriptExtensions = [".ts", ".tsx", ".d.ts"];
+    /** Must have ".d.ts" first because if ".ts" goes first, that will be detected as the extension instead of ".d.ts". */
+    ts.supportedTypescriptExtensionsForExtractExtension = [".d.ts", ".ts", ".tsx"];
     ts.supportedJavascriptExtensions = [".js", ".jsx"];
     var allSupportedExtensions = ts.supportedTypeScriptExtensions.concat(ts.supportedJavascriptExtensions);
     function getSupportedExtensions(options) {
@@ -2322,9 +2338,13 @@ var ts;
     }
     ts.removeFileExtension = removeFileExtension;
     function tryRemoveExtension(path, extension) {
-        return fileExtensionIs(path, extension) ? path.substring(0, path.length - extension.length) : undefined;
+        return fileExtensionIs(path, extension) ? removeExtension(path, extension) : undefined;
     }
     ts.tryRemoveExtension = tryRemoveExtension;
+    function removeExtension(path, extension) {
+        return path.substring(0, path.length - extension.length);
+    }
+    ts.removeExtension = removeExtension;
     function isJsxOrTsxExtension(ext) {
         return ext === ".jsx" || ext === ".tsx";
     }
@@ -3374,6 +3394,7 @@ var ts;
         Cannot_find_type_definition_file_for_0: { code: 2688, category: ts.DiagnosticCategory.Error, key: "Cannot_find_type_definition_file_for_0_2688", message: "Cannot find type definition file for '{0}'." },
         Cannot_extend_an_interface_0_Did_you_mean_implements: { code: 2689, category: ts.DiagnosticCategory.Error, key: "Cannot_extend_an_interface_0_Did_you_mean_implements_2689", message: "Cannot extend an interface '{0}'. Did you mean 'implements'?" },
         A_class_must_be_declared_after_its_base_class: { code: 2690, category: ts.DiagnosticCategory.Error, key: "A_class_must_be_declared_after_its_base_class_2690", message: "A class must be declared after its base class." },
+        An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead: { code: 2691, category: ts.DiagnosticCategory.Error, key: "An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead_2691", message: "An import path cannot end with a '{0}' extension. Consider importing '{1}' instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: ts.DiagnosticCategory.Error, key: "Import_declaration_0_is_using_private_name_1_4000", message: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_class_has_or_is_using_private_name_1_4002", message: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: ts.DiagnosticCategory.Error, key: "Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1_4004", message: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -7813,6 +7834,11 @@ var ts;
         return ts.forEach(ts.supportedTypeScriptExtensions, function (extension) { return ts.fileExtensionIs(fileName, extension); });
     }
     ts.hasTypeScriptFileExtension = hasTypeScriptFileExtension;
+    /** Return ".ts", ".d.ts", or ".tsx", if that is the extension. */
+    function tryExtractTypeScriptExtension(fileName) {
+        return ts.find(ts.supportedTypescriptExtensionsForExtractExtension, function (extension) { return ts.fileExtensionIs(fileName, extension); });
+    }
+    ts.tryExtractTypeScriptExtension = tryExtractTypeScriptExtension;
     /**
      * Replace each instance of non-ascii characters by one, two, three, or four escape sequences
      * representing the UTF-8 encoding of the character, and return the expanded char code list.
@@ -11188,6 +11214,7 @@ var ts;
          *      6) - UnaryExpression[?yield]
          *      7) ~ UnaryExpression[?yield]
          *      8) ! UnaryExpression[?yield]
+         *      9) [+Await] await UnaryExpression[?yield]
          */
         function parseSimpleUnaryExpression() {
             switch (token()) {
@@ -11202,6 +11229,8 @@ var ts;
                     return parseTypeOfExpression();
                 case 103 /* VoidKeyword */:
                     return parseVoidExpression();
+                case 119 /* AwaitKeyword */:
+                    return parseAwaitExpression();
                 case 25 /* LessThanToken */:
                     // This is modified UnaryExpression grammar in TypeScript
                     //  UnaryExpression (modified):
@@ -17373,7 +17402,7 @@ var ts;
             }
         }
         function getDeclarationOfAliasSymbol(symbol) {
-            return ts.find(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
+            return ts.findMap(symbol.declarations, function (d) { return ts.isAliasSymbolDeclaration(d) ? d : undefined; });
         }
         function getTargetOfImportEqualsDeclaration(node) {
             if (node.moduleReference.kind === 240 /* ExternalModuleReference */) {
@@ -17677,7 +17706,14 @@ var ts;
             }
             if (moduleNotFoundError) {
                 // report errors only if it was requested
-                error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                var tsExtension = ts.tryExtractTypeScriptExtension(moduleName);
+                if (tsExtension) {
+                    var diag = ts.Diagnostics.An_import_path_cannot_end_with_a_0_extension_Consider_importing_1_instead;
+                    error(moduleReferenceLiteral, diag, tsExtension, ts.removeExtension(moduleName, tsExtension));
+                }
+                else {
+                    error(moduleReferenceLiteral, moduleNotFoundError, moduleName);
+                }
             }
             return undefined;
         }
@@ -19227,7 +19263,7 @@ var ts;
             }
             // If the declaration specifies a binding pattern, use the type implied by the binding pattern
             if (ts.isBindingPattern(declaration.name)) {
-                return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ false);
+                return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ false, /*reportErrors*/ true);
             }
             // No type specified and nothing can be inferred
             return undefined;
@@ -19235,22 +19271,20 @@ var ts;
         // Return the type implied by a binding pattern element. This is the type of the initializer of the element if
         // one is present. Otherwise, if the element is itself a binding pattern, it is the type implied by the binding
         // pattern. Otherwise, it is the type any.
-        function getTypeFromBindingElement(element, includePatternInType) {
+        function getTypeFromBindingElement(element, includePatternInType, reportErrors) {
             if (element.initializer) {
-                var type = checkExpressionCached(element.initializer);
-                reportErrorsFromWidening(element, type);
-                return getWidenedType(type);
+                return checkExpressionCached(element.initializer);
             }
             if (ts.isBindingPattern(element.name)) {
-                return getTypeFromBindingPattern(element.name, includePatternInType);
+                return getTypeFromBindingPattern(element.name, includePatternInType, reportErrors);
             }
-            if (compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
+            if (reportErrors && compilerOptions.noImplicitAny && !declarationBelongsToPrivateAmbientMember(element)) {
                 reportImplicitAnyError(element, anyType);
             }
             return anyType;
         }
         // Return the type implied by an object binding pattern
-        function getTypeFromObjectBindingPattern(pattern, includePatternInType) {
+        function getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors) {
             var members = ts.createMap();
             var hasComputedProperties = false;
             ts.forEach(pattern.elements, function (e) {
@@ -19263,7 +19297,7 @@ var ts;
                 var text = getTextOfPropertyName(name);
                 var flags = 4 /* Property */ | 67108864 /* Transient */ | (e.initializer ? 536870912 /* Optional */ : 0);
                 var symbol = createSymbol(flags, text);
-                symbol.type = getTypeFromBindingElement(e, includePatternInType);
+                symbol.type = getTypeFromBindingElement(e, includePatternInType, reportErrors);
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
@@ -19277,13 +19311,13 @@ var ts;
             return result;
         }
         // Return the type implied by an array binding pattern
-        function getTypeFromArrayBindingPattern(pattern, includePatternInType) {
+        function getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors) {
             var elements = pattern.elements;
             if (elements.length === 0 || elements[elements.length - 1].dotDotDotToken) {
                 return languageVersion >= 2 /* ES6 */ ? createIterableType(anyType) : anyArrayType;
             }
             // If the pattern has at least one element, and no rest element, then it should imply a tuple type.
-            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 /* OmittedExpression */ ? anyType : getTypeFromBindingElement(e, includePatternInType); });
+            var elementTypes = ts.map(elements, function (e) { return e.kind === 193 /* OmittedExpression */ ? anyType : getTypeFromBindingElement(e, includePatternInType, reportErrors); });
             if (includePatternInType) {
                 var result = createNewTupleType(elementTypes);
                 result.pattern = pattern;
@@ -19298,10 +19332,10 @@ var ts;
         // used as the contextual type of an initializer associated with the binding pattern. Also, for a destructuring
         // parameter with no type annotation or initializer, the type implied by the binding pattern becomes the type of
         // the parameter.
-        function getTypeFromBindingPattern(pattern, includePatternInType) {
+        function getTypeFromBindingPattern(pattern, includePatternInType, reportErrors) {
             return pattern.kind === 167 /* ObjectBindingPattern */
-                ? getTypeFromObjectBindingPattern(pattern, includePatternInType)
-                : getTypeFromArrayBindingPattern(pattern, includePatternInType);
+                ? getTypeFromObjectBindingPattern(pattern, includePatternInType, reportErrors)
+                : getTypeFromArrayBindingPattern(pattern, includePatternInType, reportErrors);
         }
         // Return the type associated with a variable, parameter, or property declaration. In the simple case this is the type
         // specified in a type annotation or inferred from an initializer. However, in the case of a destructuring declaration it
@@ -25069,7 +25103,7 @@ var ts;
                     }
                 }
                 if (ts.isBindingPattern(declaration.name)) {
-                    return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true);
+                    return getTypeFromBindingPattern(declaration.name, /*includePatternInType*/ true, /*reportErrors*/ false);
                 }
                 if (ts.isBindingPattern(declaration.parent)) {
                     var parentDeclaration = declaration.parent.parent;
@@ -29299,12 +29333,7 @@ var ts;
                 checkSignatureDeclaration(node);
                 if (node.kind === 149 /* GetAccessor */) {
                     if (!ts.isInAmbientContext(node) && ts.nodeIsPresent(node.body) && (node.flags & 32768 /* HasImplicitReturn */)) {
-                        if (node.flags & 65536 /* HasExplicitReturn */) {
-                            if (compilerOptions.noImplicitReturns) {
-                                error(node.name, ts.Diagnostics.Not_all_code_paths_return_a_value);
-                            }
-                        }
-                        else {
+                        if (!(node.flags & 65536 /* HasExplicitReturn */)) {
                             error(node.name, ts.Diagnostics.A_get_accessor_must_return_a_value);
                         }
                     }
@@ -29333,7 +29362,10 @@ var ts;
                         checkAccessorDeclarationTypesIdentical(node, otherAccessor, getThisTypeOfDeclaration, ts.Diagnostics.get_and_set_accessor_must_have_the_same_this_type);
                     }
                 }
-                getTypeOfAccessors(getSymbolOfNode(node));
+                var returnType = getTypeOfAccessors(getSymbolOfNode(node));
+                if (node.kind === 149 /* GetAccessor */) {
+                    checkAllCodePathsInNonVoidFunctionReturnOrThrow(node, returnType);
+                }
             }
             if (node.parent.kind !== 171 /* ObjectLiteralExpression */) {
                 checkSourceElement(node.body);
@@ -44413,22 +44445,24 @@ var ts;
      * in cases when we know upfront that all load attempts will fail (because containing folder does not exists) however we still need to record all failed lookup locations.
      */
     function loadModuleFromFile(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
-        // First try to keep/add an extension: importing "./foo.ts" can be matched by a file "./foo.ts", and "./foo" by "./foo.d.ts"
-        var resolvedByAddingOrKeepingExtension = loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
-        if (resolvedByAddingOrKeepingExtension) {
-            return resolvedByAddingOrKeepingExtension;
+        // First, try adding an extension. An import of "foo" could be matched by a file "foo.ts", or "foo.js" by "foo.js.ts"
+        var resolvedByAddingExtension = tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state);
+        if (resolvedByAddingExtension) {
+            return resolvedByAddingExtension;
         }
-        // Then try stripping a ".js" or ".jsx" extension and replacing it with a TypeScript one, e.g. "./foo.js" can be matched by "./foo.ts" or "./foo.d.ts"
+        // If that didn't work, try stripping a ".js" or ".jsx" extension and replacing it with a TypeScript one;
+        // e.g. "./foo.js" can be matched by "./foo.ts" or "./foo.d.ts"
         if (ts.hasJavaScriptFileExtension(candidate)) {
             var extensionless = ts.removeFileExtension(candidate);
             if (state.traceEnabled) {
                 var extension = candidate.substring(extensionless.length);
                 trace(state.host, ts.Diagnostics.File_name_0_has_a_1_extension_stripping_it, candidate, extension);
             }
-            return loadModuleFromFileWorker(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
+            return tryAddingExtensions(extensionless, extensions, failedLookupLocation, onlyRecordFailures, state);
         }
     }
-    function loadModuleFromFileWorker(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
+    /** Try to return an existing file that adds one of the `extensions` to `candidate`. */
+    function tryAddingExtensions(candidate, extensions, failedLookupLocation, onlyRecordFailures, state) {
         if (!onlyRecordFailures) {
             // check if containing folder exists - if it doesn't then just record failures for all supported extensions without disk probing
             var directory = ts.getDirectoryPath(candidate);
@@ -44436,25 +44470,24 @@ var ts;
                 onlyRecordFailures = !directoryProbablyExists(directory, state.host);
             }
         }
-        return ts.forEach(extensions, tryLoad);
-        function tryLoad(ext) {
-            if (state.skipTsx && ts.isJsxOrTsxExtension(ext)) {
-                return undefined;
+        return ts.forEach(extensions, function (ext) {
+            return !(state.skipTsx && ts.isJsxOrTsxExtension(ext)) && tryFile(candidate + ext, failedLookupLocation, onlyRecordFailures, state);
+        });
+    }
+    /** Return the file if it exists. */
+    function tryFile(fileName, failedLookupLocation, onlyRecordFailures, state) {
+        if (!onlyRecordFailures && state.host.fileExists(fileName)) {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
             }
-            var fileName = ts.fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
-            if (!onlyRecordFailures && state.host.fileExists(fileName)) {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
-                }
-                return fileName;
-            }
-            else {
-                if (state.traceEnabled) {
-                    trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
-                }
-                failedLookupLocation.push(fileName);
-                return undefined;
+            return fileName;
+        }
+        else {
+            if (state.traceEnabled) {
+                trace(state.host, ts.Diagnostics.File_0_does_not_exist, fileName);
             }
+            failedLookupLocation.push(fileName);
+            return undefined;
         }
     }
     function loadNodeModuleFromDirectory(extensions, candidate, failedLookupLocation, onlyRecordFailures, state) {
@@ -44466,7 +44499,9 @@ var ts;
             }
             var typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
             if (typesFile) {
-                var result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host), state);
+                var onlyRecordFailures_1 = !directoryProbablyExists(ts.getDirectoryPath(typesFile), state.host);
+                // The package.json "typings" property must specify the file with extension, so just try that exact filename.
+                var result = tryFile(typesFile, failedLookupLocation, onlyRecordFailures_1, state);
                 if (result) {
                     return result;
                 }
@@ -56673,6 +56708,27 @@ var ts;
             }
             if (!documentation) {
                 documentation = symbol.getDocumentationComment();
+                if (documentation.length === 0 && symbol.flags & 4 /* Property */) {
+                    // For some special property access expressions like `experts.foo = foo` or `module.exports.foo = foo`
+                    // there documentation comments might be attached to the right hand side symbol of their declarations.
+                    // The pattern of such special property access is that the parent symbol is the symbol of the file.
+                    if (symbol.parent && ts.forEach(symbol.parent.declarations, function (declaration) { return declaration.kind === 256 /* SourceFile */; })) {
+                        for (var _i = 0, _a = symbol.declarations; _i < _a.length; _i++) {
+                            var declaration = _a[_i];
+                            if (!declaration.parent || declaration.parent.kind !== 187 /* BinaryExpression */) {
+                                continue;
+                            }
+                            var rhsSymbol = program.getTypeChecker().getSymbolAtLocation(declaration.parent.right);
+                            if (!rhsSymbol) {
+                                continue;
+                            }
+                            documentation = rhsSymbol.getDocumentationComment();
+                            if (documentation.length > 0) {
+                                break;
+                            }
+                        }
+                    }
+                }
             }
             return { displayParts: displayParts, documentation: documentation, symbolKind: symbolKind };
             function addNewLineIfDisplayPartsExist() {