diff --git a/lib/tsc.js b/lib/tsc.js
index 512fecfcd2c..54e563e80ce 100644
--- a/lib/tsc.js
+++ b/lib/tsc.js
@@ -60,7 +60,7 @@ var __makeTemplateObject = (this && this.__makeTemplateObject) || function (cook
 var ts;
 (function (ts) {
     ts.versionMajorMinor = "3.4";
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     ts.emptyArray = [];
@@ -9899,7 +9899,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 ? type.objectFlags : 0;
+        return type.flags & 3899392 ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -25788,10 +25788,10 @@ var ts;
         var wildcardType = createIntrinsicType(1, "any");
         var errorType = createIntrinsicType(1, "error");
         var unknownType = createIntrinsicType(2, "unknown");
-        var undefinedType = createNullableType(32768, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768, "undefined", 131072);
-        var nullType = createNullableType(65536, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536, "null", 131072);
+        var undefinedType = createIntrinsicType(32768, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768, "undefined", 131072);
+        var nullType = createIntrinsicType(65536, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536, "null", 131072);
         var stringType = createIntrinsicType(4, "string");
         var numberType = createIntrinsicType(8, "number");
         var bigintType = createIntrinsicType(64, "bigint");
@@ -25815,6 +25815,7 @@ var ts;
         var voidType = createIntrinsicType(16384, "void");
         var neverType = createIntrinsicType(131072, "never");
         var silentNeverType = createIntrinsicType(131072, "never");
+        var nonInferrableType = createIntrinsicType(131072, "never", 524288);
         var implicitNeverType = createIntrinsicType(131072, "never");
         var nonPrimitiveType = createIntrinsicType(67108864, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -27542,13 +27543,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -33598,7 +33596,7 @@ var ts;
             return newResult;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
-            if (falseType.flags & 131072 && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) {
                     return trueType;
                 }
@@ -33606,7 +33604,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) {
                     return neverType;
                 }
@@ -36898,7 +36896,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0);
             var numberIndexInfo = getIndexInfoOfType(type, 1);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384);
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 | 524288));
             return result;
         }
         function getWidenedType(type) {
@@ -37172,16 +37170,9 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0)) {
+            if (ts.getObjectFlags(source) & 524288 || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0)) {
                 return undefined;
             }
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288) {
-                    return undefined;
-                }
-            }
             if (isArrayType(source)) {
                 return createArrayType(inferReverseMappedType(source.typeArguments[0], target, constraint), isReadonlyArrayType(source));
             }
@@ -37208,16 +37199,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216))) return [3, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3, 3];
@@ -37410,20 +37401,32 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728) {
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    if (target.flags & 1048576 ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576) {
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -37573,8 +37576,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -41924,7 +41927,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -42581,7 +42584,7 @@ var ts;
                 checkGrammarArguments(node.arguments);
             var signature = getResolvedSignature(node, undefined, checkMode);
             if (signature === resolvingSignature) {
-                return silentNeverType;
+                return nonInferrableType;
             }
             if (node.expression.kind === 98) {
                 return voidType;
@@ -43570,8 +43573,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -47214,8 +47217,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -49380,7 +49383,7 @@ var ts;
             if (autoArrayType === emptyObjectType) {
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", 1);
             if (augmentations) {
@@ -53915,27 +53918,27 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, undefined, undefined, undefined, getAccessor.parameters, undefined, getAccessor.body);
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, undefined, undefined, undefined, setAccessor.parameters, undefined, setAccessor.body);
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), firstAccessor);
             return ts.aggregateTransformFlags(expression);
         }
@@ -57301,8 +57304,8 @@ var ts;
                 && member.initializer !== undefined;
         }
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -57312,8 +57315,8 @@ var ts;
         }
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));
diff --git a/lib/tsserver.js b/lib/tsserver.js
index 1c39c0df249..81e0cb7e64c 100644
--- a/lib/tsserver.js
+++ b/lib/tsserver.js
@@ -85,7 +85,7 @@ var ts;
     // If changing the text in this section, be sure to test `configureNightly` too.
     ts.versionMajorMinor = "3.4";
     /** The version of the TypeScript compiler release */
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     /* @internal */
@@ -3490,7 +3490,7 @@ var ts;
         TypeFlags[TypeFlags["Instantiable"] = 63176704] = "Instantiable";
         TypeFlags[TypeFlags["StructuredOrInstantiable"] = 66846720] = "StructuredOrInstantiable";
         /* @internal */
-        TypeFlags[TypeFlags["ObjectFlagsType"] = 3768320] = "ObjectFlagsType";
+        TypeFlags[TypeFlags["ObjectFlagsType"] = 3899392] = "ObjectFlagsType";
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         TypeFlags[TypeFlags["Narrowable"] = 133970943] = "Narrowable";
@@ -3538,7 +3538,7 @@ var ts;
         /* @internal */
         ObjectFlags[ObjectFlags["ContainsObjectLiteral"] = 262144] = "ContainsObjectLiteral";
         /* @internal */
-        ObjectFlags[ObjectFlags["ContainsAnyFunctionType"] = 524288] = "ContainsAnyFunctionType";
+        ObjectFlags[ObjectFlags["NonInferrableType"] = 524288] = "NonInferrableType";
         ObjectFlags[ObjectFlags["ClassOrInterface"] = 3] = "ClassOrInterface";
         /* @internal */
         ObjectFlags[ObjectFlags["RequiresWidening"] = 393216] = "RequiresWidening";
@@ -12614,7 +12614,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 /* ObjectFlagsType */ ? type.objectFlags : 0;
+        return type.flags & 3899392 /* ObjectFlagsType */ ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -31471,10 +31471,10 @@ var ts;
         var wildcardType = createIntrinsicType(1 /* Any */, "any");
         var errorType = createIntrinsicType(1 /* Any */, "error");
         var unknownType = createIntrinsicType(2 /* Unknown */, "unknown");
-        var undefinedType = createNullableType(32768 /* Undefined */, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
-        var nullType = createNullableType(65536 /* Null */, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
+        var undefinedType = createIntrinsicType(32768 /* Undefined */, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
+        var nullType = createIntrinsicType(65536 /* Null */, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
         var stringType = createIntrinsicType(4 /* String */, "string");
         var numberType = createIntrinsicType(8 /* Number */, "number");
         var bigintType = createIntrinsicType(64 /* BigInt */, "bigint");
@@ -31500,6 +31500,7 @@ var ts;
         var voidType = createIntrinsicType(16384 /* Void */, "void");
         var neverType = createIntrinsicType(131072 /* Never */, "never");
         var silentNeverType = createIntrinsicType(131072 /* Never */, "never");
+        var nonInferrableType = createIntrinsicType(131072 /* Never */, "never", 524288 /* NonInferrableType */);
         var implicitNeverType = createIntrinsicType(131072 /* Never */, "never");
         var nonPrimitiveType = createIntrinsicType(67108864 /* NonPrimitive */, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -31516,7 +31517,7 @@ var ts;
         var anyFunctionType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+        anyFunctionType.objectFlags |= 524288 /* NonInferrableType */;
         var noConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var circularConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var resolvingDefaultType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
@@ -33618,13 +33619,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -40457,7 +40455,7 @@ var ts;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 /* Never */ && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 /* Any */ || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -40465,7 +40463,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 /* Never */ && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1 /* Any */) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }
@@ -44212,7 +44210,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0 /* String */);
             var numberIndexInfo = getIndexInfoOfType(type, 1 /* Number */);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384 /* JSLiteral */); // Retain js literal flag through widening
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 /* JSLiteral */ | 524288 /* NonInferrableType */)); // Retain js literal flag through widening
             return result;
         }
         function getWidenedType(type) {
@@ -44513,17 +44511,10 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288 /* ContainsAnyFunctionType */) {
-                    return undefined;
-                }
+            if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -44555,16 +44546,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 /* Intersection */ ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3 /*break*/, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3 /*break*/, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216 /* Optional */))) return [3 /*break*/, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3 /*break*/, 3];
@@ -44688,7 +44679,7 @@ var ts;
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
+                    if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     var inference = getInferenceInfoForType(target);
@@ -44788,24 +44779,40 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728 /* UnionOrIntersection */) {
+                    // We infer from types that are not naked type variables first so that inferences we
+                    // make from nested naked type variables and given slightly higher priority by virtue
+                    // of being first in the candidates array.
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
-                        // Inferences directly to naked type variables are given lower priority as they are
-                        // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
-                        // we want to infer string for T, not Promise<string> | string.
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1 /* NakedTypeVariable */;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    // Inferences directly to naked type variables are given lower priority as they are
+                    // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
+                    // we want to infer string for T, not Promise<string> | string. For intersection types
+                    // we only infer to single naked type variables.
+                    if (target.flags & 1048576 /* Union */ ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1 /* NakedTypeVariable */;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576 /* Union */) {
                     // Source is a union or intersection type, infer from each constituent type
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -44984,8 +44991,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -44998,7 +45005,7 @@ var ts;
                 var sourceLen = sourceSignatures.length;
                 var targetLen = targetSignatures.length;
                 var len = sourceLen < targetLen ? sourceLen : targetLen;
-                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */);
+                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* NonInferrableType */);
                 for (var i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -50158,7 +50165,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -50579,7 +50586,7 @@ var ts;
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & 8 /* SkipGenericFunctions */ && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -51002,8 +51009,8 @@ var ts;
             var signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
             if (node.expression.kind === 98 /* SuperKeyword */) {
                 return voidType;
@@ -51742,7 +51749,7 @@ var ts;
                     var returnType = getReturnTypeFromBody(node, checkMode);
                     var returnOnlySignature = createSignature(undefined, undefined, undefined, ts.emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     var returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], ts.emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+                    returnOnlyType.objectFlags |= 524288 /* NonInferrableType */;
                     return links_1.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;
@@ -52124,8 +52131,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -56483,8 +56490,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -58931,7 +58938,7 @@ var ts;
                 // autoArrayType is used as a marker, so even if global Array type is not defined, it needs to be a unique type
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", /*arity*/ 1);
             if (augmentations) {
@@ -63754,7 +63761,7 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, 
                 /*asteriskToken*/ undefined, 
@@ -63765,7 +63772,7 @@ var ts;
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, 
@@ -63777,15 +63784,15 @@ var ts;
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), 
             /*typeArguments*/ undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), 
             /*location*/ firstAccessor);
             return ts.aggregateTransformFlags(expression);
@@ -68269,8 +68276,8 @@ var ts;
          * @param receiver The receiver on which each property should be assigned.
          */
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -68286,8 +68293,8 @@ var ts;
          */
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));
diff --git a/lib/tsserverlibrary.js b/lib/tsserverlibrary.js
index 9506319a806..54c3e4a50d1 100644
--- a/lib/tsserverlibrary.js
+++ b/lib/tsserverlibrary.js
@@ -84,7 +84,7 @@ var ts;
     // If changing the text in this section, be sure to test `configureNightly` too.
     ts.versionMajorMinor = "3.4";
     /** The version of the TypeScript compiler release */
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     /* @internal */
@@ -3489,7 +3489,7 @@ var ts;
         TypeFlags[TypeFlags["Instantiable"] = 63176704] = "Instantiable";
         TypeFlags[TypeFlags["StructuredOrInstantiable"] = 66846720] = "StructuredOrInstantiable";
         /* @internal */
-        TypeFlags[TypeFlags["ObjectFlagsType"] = 3768320] = "ObjectFlagsType";
+        TypeFlags[TypeFlags["ObjectFlagsType"] = 3899392] = "ObjectFlagsType";
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         TypeFlags[TypeFlags["Narrowable"] = 133970943] = "Narrowable";
@@ -3537,7 +3537,7 @@ var ts;
         /* @internal */
         ObjectFlags[ObjectFlags["ContainsObjectLiteral"] = 262144] = "ContainsObjectLiteral";
         /* @internal */
-        ObjectFlags[ObjectFlags["ContainsAnyFunctionType"] = 524288] = "ContainsAnyFunctionType";
+        ObjectFlags[ObjectFlags["NonInferrableType"] = 524288] = "NonInferrableType";
         ObjectFlags[ObjectFlags["ClassOrInterface"] = 3] = "ClassOrInterface";
         /* @internal */
         ObjectFlags[ObjectFlags["RequiresWidening"] = 393216] = "RequiresWidening";
@@ -12613,7 +12613,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 /* ObjectFlagsType */ ? type.objectFlags : 0;
+        return type.flags & 3899392 /* ObjectFlagsType */ ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -31470,10 +31470,10 @@ var ts;
         var wildcardType = createIntrinsicType(1 /* Any */, "any");
         var errorType = createIntrinsicType(1 /* Any */, "error");
         var unknownType = createIntrinsicType(2 /* Unknown */, "unknown");
-        var undefinedType = createNullableType(32768 /* Undefined */, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
-        var nullType = createNullableType(65536 /* Null */, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
+        var undefinedType = createIntrinsicType(32768 /* Undefined */, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
+        var nullType = createIntrinsicType(65536 /* Null */, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
         var stringType = createIntrinsicType(4 /* String */, "string");
         var numberType = createIntrinsicType(8 /* Number */, "number");
         var bigintType = createIntrinsicType(64 /* BigInt */, "bigint");
@@ -31499,6 +31499,7 @@ var ts;
         var voidType = createIntrinsicType(16384 /* Void */, "void");
         var neverType = createIntrinsicType(131072 /* Never */, "never");
         var silentNeverType = createIntrinsicType(131072 /* Never */, "never");
+        var nonInferrableType = createIntrinsicType(131072 /* Never */, "never", 524288 /* NonInferrableType */);
         var implicitNeverType = createIntrinsicType(131072 /* Never */, "never");
         var nonPrimitiveType = createIntrinsicType(67108864 /* NonPrimitive */, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -31515,7 +31516,7 @@ var ts;
         var anyFunctionType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+        anyFunctionType.objectFlags |= 524288 /* NonInferrableType */;
         var noConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var circularConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var resolvingDefaultType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
@@ -33617,13 +33618,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -40456,7 +40454,7 @@ var ts;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 /* Never */ && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 /* Any */ || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -40464,7 +40462,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 /* Never */ && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1 /* Any */) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }
@@ -44211,7 +44209,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0 /* String */);
             var numberIndexInfo = getIndexInfoOfType(type, 1 /* Number */);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384 /* JSLiteral */); // Retain js literal flag through widening
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 /* JSLiteral */ | 524288 /* NonInferrableType */)); // Retain js literal flag through widening
             return result;
         }
         function getWidenedType(type) {
@@ -44512,17 +44510,10 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288 /* ContainsAnyFunctionType */) {
-                    return undefined;
-                }
+            if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -44554,16 +44545,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 /* Intersection */ ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3 /*break*/, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3 /*break*/, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216 /* Optional */))) return [3 /*break*/, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3 /*break*/, 3];
@@ -44687,7 +44678,7 @@ var ts;
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
+                    if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     var inference = getInferenceInfoForType(target);
@@ -44787,24 +44778,40 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728 /* UnionOrIntersection */) {
+                    // We infer from types that are not naked type variables first so that inferences we
+                    // make from nested naked type variables and given slightly higher priority by virtue
+                    // of being first in the candidates array.
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
-                        // Inferences directly to naked type variables are given lower priority as they are
-                        // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
-                        // we want to infer string for T, not Promise<string> | string.
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1 /* NakedTypeVariable */;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    // Inferences directly to naked type variables are given lower priority as they are
+                    // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
+                    // we want to infer string for T, not Promise<string> | string. For intersection types
+                    // we only infer to single naked type variables.
+                    if (target.flags & 1048576 /* Union */ ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1 /* NakedTypeVariable */;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576 /* Union */) {
                     // Source is a union or intersection type, infer from each constituent type
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -44983,8 +44990,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -44997,7 +45004,7 @@ var ts;
                 var sourceLen = sourceSignatures.length;
                 var targetLen = targetSignatures.length;
                 var len = sourceLen < targetLen ? sourceLen : targetLen;
-                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */);
+                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* NonInferrableType */);
                 for (var i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -50157,7 +50164,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -50578,7 +50585,7 @@ var ts;
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & 8 /* SkipGenericFunctions */ && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -51001,8 +51008,8 @@ var ts;
             var signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
             if (node.expression.kind === 98 /* SuperKeyword */) {
                 return voidType;
@@ -51741,7 +51748,7 @@ var ts;
                     var returnType = getReturnTypeFromBody(node, checkMode);
                     var returnOnlySignature = createSignature(undefined, undefined, undefined, ts.emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     var returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], ts.emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+                    returnOnlyType.objectFlags |= 524288 /* NonInferrableType */;
                     return links_1.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;
@@ -52123,8 +52130,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -56482,8 +56489,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -58930,7 +58937,7 @@ var ts;
                 // autoArrayType is used as a marker, so even if global Array type is not defined, it needs to be a unique type
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", /*arity*/ 1);
             if (augmentations) {
@@ -63753,7 +63760,7 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, 
                 /*asteriskToken*/ undefined, 
@@ -63764,7 +63771,7 @@ var ts;
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, 
@@ -63776,15 +63783,15 @@ var ts;
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), 
             /*typeArguments*/ undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), 
             /*location*/ firstAccessor);
             return ts.aggregateTransformFlags(expression);
@@ -68268,8 +68275,8 @@ var ts;
          * @param receiver The receiver on which each property should be assigned.
          */
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -68285,8 +68292,8 @@ var ts;
          */
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));
diff --git a/lib/typescript.js b/lib/typescript.js
index da4767072f7..1e462e60447 100644
--- a/lib/typescript.js
+++ b/lib/typescript.js
@@ -75,7 +75,7 @@ var ts;
     // If changing the text in this section, be sure to test `configureNightly` too.
     ts.versionMajorMinor = "3.4";
     /** The version of the TypeScript compiler release */
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     /* @internal */
@@ -3480,7 +3480,7 @@ var ts;
         TypeFlags[TypeFlags["Instantiable"] = 63176704] = "Instantiable";
         TypeFlags[TypeFlags["StructuredOrInstantiable"] = 66846720] = "StructuredOrInstantiable";
         /* @internal */
-        TypeFlags[TypeFlags["ObjectFlagsType"] = 3768320] = "ObjectFlagsType";
+        TypeFlags[TypeFlags["ObjectFlagsType"] = 3899392] = "ObjectFlagsType";
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         TypeFlags[TypeFlags["Narrowable"] = 133970943] = "Narrowable";
@@ -3528,7 +3528,7 @@ var ts;
         /* @internal */
         ObjectFlags[ObjectFlags["ContainsObjectLiteral"] = 262144] = "ContainsObjectLiteral";
         /* @internal */
-        ObjectFlags[ObjectFlags["ContainsAnyFunctionType"] = 524288] = "ContainsAnyFunctionType";
+        ObjectFlags[ObjectFlags["NonInferrableType"] = 524288] = "NonInferrableType";
         ObjectFlags[ObjectFlags["ClassOrInterface"] = 3] = "ClassOrInterface";
         /* @internal */
         ObjectFlags[ObjectFlags["RequiresWidening"] = 393216] = "RequiresWidening";
@@ -12604,7 +12604,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 /* ObjectFlagsType */ ? type.objectFlags : 0;
+        return type.flags & 3899392 /* ObjectFlagsType */ ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -31461,10 +31461,10 @@ var ts;
         var wildcardType = createIntrinsicType(1 /* Any */, "any");
         var errorType = createIntrinsicType(1 /* Any */, "error");
         var unknownType = createIntrinsicType(2 /* Unknown */, "unknown");
-        var undefinedType = createNullableType(32768 /* Undefined */, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
-        var nullType = createNullableType(65536 /* Null */, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
+        var undefinedType = createIntrinsicType(32768 /* Undefined */, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
+        var nullType = createIntrinsicType(65536 /* Null */, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
         var stringType = createIntrinsicType(4 /* String */, "string");
         var numberType = createIntrinsicType(8 /* Number */, "number");
         var bigintType = createIntrinsicType(64 /* BigInt */, "bigint");
@@ -31490,6 +31490,7 @@ var ts;
         var voidType = createIntrinsicType(16384 /* Void */, "void");
         var neverType = createIntrinsicType(131072 /* Never */, "never");
         var silentNeverType = createIntrinsicType(131072 /* Never */, "never");
+        var nonInferrableType = createIntrinsicType(131072 /* Never */, "never", 524288 /* NonInferrableType */);
         var implicitNeverType = createIntrinsicType(131072 /* Never */, "never");
         var nonPrimitiveType = createIntrinsicType(67108864 /* NonPrimitive */, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -31506,7 +31507,7 @@ var ts;
         var anyFunctionType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+        anyFunctionType.objectFlags |= 524288 /* NonInferrableType */;
         var noConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var circularConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var resolvingDefaultType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
@@ -33608,13 +33609,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -40447,7 +40445,7 @@ var ts;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 /* Never */ && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 /* Any */ || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -40455,7 +40453,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 /* Never */ && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1 /* Any */) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }
@@ -44202,7 +44200,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0 /* String */);
             var numberIndexInfo = getIndexInfoOfType(type, 1 /* Number */);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384 /* JSLiteral */); // Retain js literal flag through widening
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 /* JSLiteral */ | 524288 /* NonInferrableType */)); // Retain js literal flag through widening
             return result;
         }
         function getWidenedType(type) {
@@ -44503,17 +44501,10 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288 /* ContainsAnyFunctionType */) {
-                    return undefined;
-                }
+            if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -44545,16 +44536,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 /* Intersection */ ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3 /*break*/, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3 /*break*/, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216 /* Optional */))) return [3 /*break*/, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3 /*break*/, 3];
@@ -44678,7 +44669,7 @@ var ts;
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
+                    if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     var inference = getInferenceInfoForType(target);
@@ -44778,24 +44769,40 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728 /* UnionOrIntersection */) {
+                    // We infer from types that are not naked type variables first so that inferences we
+                    // make from nested naked type variables and given slightly higher priority by virtue
+                    // of being first in the candidates array.
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
-                        // Inferences directly to naked type variables are given lower priority as they are
-                        // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
-                        // we want to infer string for T, not Promise<string> | string.
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1 /* NakedTypeVariable */;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    // Inferences directly to naked type variables are given lower priority as they are
+                    // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
+                    // we want to infer string for T, not Promise<string> | string. For intersection types
+                    // we only infer to single naked type variables.
+                    if (target.flags & 1048576 /* Union */ ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1 /* NakedTypeVariable */;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576 /* Union */) {
                     // Source is a union or intersection type, infer from each constituent type
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -44974,8 +44981,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -44988,7 +44995,7 @@ var ts;
                 var sourceLen = sourceSignatures.length;
                 var targetLen = targetSignatures.length;
                 var len = sourceLen < targetLen ? sourceLen : targetLen;
-                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */);
+                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* NonInferrableType */);
                 for (var i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -50148,7 +50155,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -50569,7 +50576,7 @@ var ts;
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & 8 /* SkipGenericFunctions */ && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -50992,8 +50999,8 @@ var ts;
             var signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
             if (node.expression.kind === 98 /* SuperKeyword */) {
                 return voidType;
@@ -51732,7 +51739,7 @@ var ts;
                     var returnType = getReturnTypeFromBody(node, checkMode);
                     var returnOnlySignature = createSignature(undefined, undefined, undefined, ts.emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     var returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], ts.emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+                    returnOnlyType.objectFlags |= 524288 /* NonInferrableType */;
                     return links_1.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;
@@ -52114,8 +52121,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -56473,8 +56480,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -58921,7 +58928,7 @@ var ts;
                 // autoArrayType is used as a marker, so even if global Array type is not defined, it needs to be a unique type
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", /*arity*/ 1);
             if (augmentations) {
@@ -63744,7 +63751,7 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, 
                 /*asteriskToken*/ undefined, 
@@ -63755,7 +63762,7 @@ var ts;
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, 
@@ -63767,15 +63774,15 @@ var ts;
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), 
             /*typeArguments*/ undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), 
             /*location*/ firstAccessor);
             return ts.aggregateTransformFlags(expression);
@@ -68259,8 +68266,8 @@ var ts;
          * @param receiver The receiver on which each property should be assigned.
          */
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -68276,8 +68283,8 @@ var ts;
          */
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));
diff --git a/lib/typescriptServices.js b/lib/typescriptServices.js
index 6da9625d975..696cb602012 100644
--- a/lib/typescriptServices.js
+++ b/lib/typescriptServices.js
@@ -75,7 +75,7 @@ var ts;
     // If changing the text in this section, be sure to test `configureNightly` too.
     ts.versionMajorMinor = "3.4";
     /** The version of the TypeScript compiler release */
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     /* @internal */
@@ -3480,7 +3480,7 @@ var ts;
         TypeFlags[TypeFlags["Instantiable"] = 63176704] = "Instantiable";
         TypeFlags[TypeFlags["StructuredOrInstantiable"] = 66846720] = "StructuredOrInstantiable";
         /* @internal */
-        TypeFlags[TypeFlags["ObjectFlagsType"] = 3768320] = "ObjectFlagsType";
+        TypeFlags[TypeFlags["ObjectFlagsType"] = 3899392] = "ObjectFlagsType";
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         TypeFlags[TypeFlags["Narrowable"] = 133970943] = "Narrowable";
@@ -3528,7 +3528,7 @@ var ts;
         /* @internal */
         ObjectFlags[ObjectFlags["ContainsObjectLiteral"] = 262144] = "ContainsObjectLiteral";
         /* @internal */
-        ObjectFlags[ObjectFlags["ContainsAnyFunctionType"] = 524288] = "ContainsAnyFunctionType";
+        ObjectFlags[ObjectFlags["NonInferrableType"] = 524288] = "NonInferrableType";
         ObjectFlags[ObjectFlags["ClassOrInterface"] = 3] = "ClassOrInterface";
         /* @internal */
         ObjectFlags[ObjectFlags["RequiresWidening"] = 393216] = "RequiresWidening";
@@ -12604,7 +12604,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 /* ObjectFlagsType */ ? type.objectFlags : 0;
+        return type.flags & 3899392 /* ObjectFlagsType */ ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -31461,10 +31461,10 @@ var ts;
         var wildcardType = createIntrinsicType(1 /* Any */, "any");
         var errorType = createIntrinsicType(1 /* Any */, "error");
         var unknownType = createIntrinsicType(2 /* Unknown */, "unknown");
-        var undefinedType = createNullableType(32768 /* Undefined */, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
-        var nullType = createNullableType(65536 /* Null */, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
+        var undefinedType = createIntrinsicType(32768 /* Undefined */, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
+        var nullType = createIntrinsicType(65536 /* Null */, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
         var stringType = createIntrinsicType(4 /* String */, "string");
         var numberType = createIntrinsicType(8 /* Number */, "number");
         var bigintType = createIntrinsicType(64 /* BigInt */, "bigint");
@@ -31490,6 +31490,7 @@ var ts;
         var voidType = createIntrinsicType(16384 /* Void */, "void");
         var neverType = createIntrinsicType(131072 /* Never */, "never");
         var silentNeverType = createIntrinsicType(131072 /* Never */, "never");
+        var nonInferrableType = createIntrinsicType(131072 /* Never */, "never", 524288 /* NonInferrableType */);
         var implicitNeverType = createIntrinsicType(131072 /* Never */, "never");
         var nonPrimitiveType = createIntrinsicType(67108864 /* NonPrimitive */, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -31506,7 +31507,7 @@ var ts;
         var anyFunctionType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+        anyFunctionType.objectFlags |= 524288 /* NonInferrableType */;
         var noConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var circularConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var resolvingDefaultType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
@@ -33608,13 +33609,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -40447,7 +40445,7 @@ var ts;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 /* Never */ && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 /* Any */ || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -40455,7 +40453,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 /* Never */ && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1 /* Any */) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }
@@ -44202,7 +44200,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0 /* String */);
             var numberIndexInfo = getIndexInfoOfType(type, 1 /* Number */);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384 /* JSLiteral */); // Retain js literal flag through widening
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 /* JSLiteral */ | 524288 /* NonInferrableType */)); // Retain js literal flag through widening
             return result;
         }
         function getWidenedType(type) {
@@ -44503,17 +44501,10 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288 /* ContainsAnyFunctionType */) {
-                    return undefined;
-                }
+            if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -44545,16 +44536,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 /* Intersection */ ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3 /*break*/, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3 /*break*/, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216 /* Optional */))) return [3 /*break*/, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3 /*break*/, 3];
@@ -44678,7 +44669,7 @@ var ts;
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
+                    if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     var inference = getInferenceInfoForType(target);
@@ -44778,24 +44769,40 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728 /* UnionOrIntersection */) {
+                    // We infer from types that are not naked type variables first so that inferences we
+                    // make from nested naked type variables and given slightly higher priority by virtue
+                    // of being first in the candidates array.
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
-                        // Inferences directly to naked type variables are given lower priority as they are
-                        // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
-                        // we want to infer string for T, not Promise<string> | string.
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1 /* NakedTypeVariable */;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    // Inferences directly to naked type variables are given lower priority as they are
+                    // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
+                    // we want to infer string for T, not Promise<string> | string. For intersection types
+                    // we only infer to single naked type variables.
+                    if (target.flags & 1048576 /* Union */ ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1 /* NakedTypeVariable */;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576 /* Union */) {
                     // Source is a union or intersection type, infer from each constituent type
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -44974,8 +44981,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -44988,7 +44995,7 @@ var ts;
                 var sourceLen = sourceSignatures.length;
                 var targetLen = targetSignatures.length;
                 var len = sourceLen < targetLen ? sourceLen : targetLen;
-                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */);
+                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* NonInferrableType */);
                 for (var i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -50148,7 +50155,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -50569,7 +50576,7 @@ var ts;
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & 8 /* SkipGenericFunctions */ && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -50992,8 +50999,8 @@ var ts;
             var signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
             if (node.expression.kind === 98 /* SuperKeyword */) {
                 return voidType;
@@ -51732,7 +51739,7 @@ var ts;
                     var returnType = getReturnTypeFromBody(node, checkMode);
                     var returnOnlySignature = createSignature(undefined, undefined, undefined, ts.emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     var returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], ts.emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+                    returnOnlyType.objectFlags |= 524288 /* NonInferrableType */;
                     return links_1.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;
@@ -52114,8 +52121,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -56473,8 +56480,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -58921,7 +58928,7 @@ var ts;
                 // autoArrayType is used as a marker, so even if global Array type is not defined, it needs to be a unique type
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", /*arity*/ 1);
             if (augmentations) {
@@ -63744,7 +63751,7 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, 
                 /*asteriskToken*/ undefined, 
@@ -63755,7 +63762,7 @@ var ts;
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, 
@@ -63767,15 +63774,15 @@ var ts;
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), 
             /*typeArguments*/ undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), 
             /*location*/ firstAccessor);
             return ts.aggregateTransformFlags(expression);
@@ -68259,8 +68266,8 @@ var ts;
          * @param receiver The receiver on which each property should be assigned.
          */
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -68276,8 +68283,8 @@ var ts;
          */
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));
diff --git a/lib/typingsInstaller.js b/lib/typingsInstaller.js
index d7fd676a74f..779668a162a 100644
--- a/lib/typingsInstaller.js
+++ b/lib/typingsInstaller.js
@@ -76,7 +76,7 @@ var ts;
     // If changing the text in this section, be sure to test `configureNightly` too.
     ts.versionMajorMinor = "3.4";
     /** The version of the TypeScript compiler release */
-    ts.version = ts.versionMajorMinor + ".3";
+    ts.version = ts.versionMajorMinor + ".4";
 })(ts || (ts = {}));
 (function (ts) {
     /* @internal */
@@ -3481,7 +3481,7 @@ var ts;
         TypeFlags[TypeFlags["Instantiable"] = 63176704] = "Instantiable";
         TypeFlags[TypeFlags["StructuredOrInstantiable"] = 66846720] = "StructuredOrInstantiable";
         /* @internal */
-        TypeFlags[TypeFlags["ObjectFlagsType"] = 3768320] = "ObjectFlagsType";
+        TypeFlags[TypeFlags["ObjectFlagsType"] = 3899392] = "ObjectFlagsType";
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         TypeFlags[TypeFlags["Narrowable"] = 133970943] = "Narrowable";
@@ -3529,7 +3529,7 @@ var ts;
         /* @internal */
         ObjectFlags[ObjectFlags["ContainsObjectLiteral"] = 262144] = "ContainsObjectLiteral";
         /* @internal */
-        ObjectFlags[ObjectFlags["ContainsAnyFunctionType"] = 524288] = "ContainsAnyFunctionType";
+        ObjectFlags[ObjectFlags["NonInferrableType"] = 524288] = "NonInferrableType";
         ObjectFlags[ObjectFlags["ClassOrInterface"] = 3] = "ClassOrInterface";
         /* @internal */
         ObjectFlags[ObjectFlags["RequiresWidening"] = 393216] = "RequiresWidening";
@@ -12605,7 +12605,7 @@ var ts;
     }
     ts.getClassLikeDeclarationOfSymbol = getClassLikeDeclarationOfSymbol;
     function getObjectFlags(type) {
-        return type.flags & 3768320 /* ObjectFlagsType */ ? type.objectFlags : 0;
+        return type.flags & 3899392 /* ObjectFlagsType */ ? type.objectFlags : 0;
     }
     ts.getObjectFlags = getObjectFlags;
     function typeHasCallOrConstructSignatures(type, checker) {
@@ -31462,10 +31462,10 @@ var ts;
         var wildcardType = createIntrinsicType(1 /* Any */, "any");
         var errorType = createIntrinsicType(1 /* Any */, "error");
         var unknownType = createIntrinsicType(2 /* Unknown */, "unknown");
-        var undefinedType = createNullableType(32768 /* Undefined */, "undefined", 0);
-        var undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
-        var nullType = createNullableType(65536 /* Null */, "null", 0);
-        var nullWideningType = strictNullChecks ? nullType : createNullableType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
+        var undefinedType = createIntrinsicType(32768 /* Undefined */, "undefined");
+        var undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(32768 /* Undefined */, "undefined", 131072 /* ContainsWideningType */);
+        var nullType = createIntrinsicType(65536 /* Null */, "null");
+        var nullWideningType = strictNullChecks ? nullType : createIntrinsicType(65536 /* Null */, "null", 131072 /* ContainsWideningType */);
         var stringType = createIntrinsicType(4 /* String */, "string");
         var numberType = createIntrinsicType(8 /* Number */, "number");
         var bigintType = createIntrinsicType(64 /* BigInt */, "bigint");
@@ -31491,6 +31491,7 @@ var ts;
         var voidType = createIntrinsicType(16384 /* Void */, "void");
         var neverType = createIntrinsicType(131072 /* Never */, "never");
         var silentNeverType = createIntrinsicType(131072 /* Never */, "never");
+        var nonInferrableType = createIntrinsicType(131072 /* Never */, "never", 524288 /* NonInferrableType */);
         var implicitNeverType = createIntrinsicType(131072 /* Never */, "never");
         var nonPrimitiveType = createIntrinsicType(67108864 /* NonPrimitive */, "object");
         var stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -31507,7 +31508,7 @@ var ts;
         var anyFunctionType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+        anyFunctionType.objectFlags |= 524288 /* NonInferrableType */;
         var noConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var circularConstraintType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
         var resolvingDefaultType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
@@ -33609,13 +33610,10 @@ var ts;
             result.id = typeCount;
             return result;
         }
-        function createIntrinsicType(kind, intrinsicName) {
+        function createIntrinsicType(kind, intrinsicName, objectFlags) {
+            if (objectFlags === void 0) { objectFlags = 0; }
             var type = createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-        function createNullableType(kind, intrinsicName, objectFlags) {
-            var type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -40448,7 +40446,7 @@ var ts;
         }
         function getConditionalTypeWorker(root, mapper, checkType, extendsType, trueType, falseType) {
             // Simplifications for types of the form `T extends U ? T : never` and `T extends U ? never : T`.
-            if (falseType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(trueType), getActualTypeVariable(checkType))) {
+            if (falseType.flags & 131072 /* Never */ && getActualTypeVariable(trueType) === getActualTypeVariable(checkType)) {
                 if (checkType.flags & 1 /* Any */ || isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return trueType;
                 }
@@ -40456,7 +40454,7 @@ var ts;
                     return neverType;
                 }
             }
-            else if (trueType.flags & 131072 /* Never */ && isTypeIdenticalTo(getActualTypeVariable(falseType), getActualTypeVariable(checkType))) {
+            else if (trueType.flags & 131072 /* Never */ && getActualTypeVariable(falseType) === getActualTypeVariable(checkType)) {
                 if (!(checkType.flags & 1 /* Any */) && isTypeAssignableTo(getRestrictiveInstantiation(checkType), getRestrictiveInstantiation(extendsType))) { // Always true
                     return neverType;
                 }
@@ -44203,7 +44201,7 @@ var ts;
             var stringIndexInfo = getIndexInfoOfType(type, 0 /* String */);
             var numberIndexInfo = getIndexInfoOfType(type, 1 /* Number */);
             var result = createAnonymousType(type.symbol, members, ts.emptyArray, ts.emptyArray, stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly), numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
-            result.objectFlags |= (ts.getObjectFlags(type) & 16384 /* JSLiteral */); // Retain js literal flag through widening
+            result.objectFlags |= (ts.getObjectFlags(type) & (16384 /* JSLiteral */ | 524288 /* NonInferrableType */)); // Retain js literal flag through widening
             return result;
         }
         function getWidenedType(type) {
@@ -44504,17 +44502,10 @@ var ts;
             return type;
         }
         function createReverseMappedType(source, target, constraint) {
-            var properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (var _i = 0, properties_3 = properties; _i < properties_3.length; _i++) {
-                var prop = properties_3[_i];
-                if (ts.getObjectFlags(getTypeOfSymbol(prop)) & 524288 /* ContainsAnyFunctionType */) {
-                    return undefined;
-                }
+            if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, 0 /* String */)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -44546,16 +44537,16 @@ var ts;
             return getTypeFromInference(inference);
         }
         function getUnmatchedProperties(source, target, requireOptionalProperties, matchDiscriminantProperties) {
-            var properties, _i, properties_4, targetProp, sourceProp, targetType, sourceType;
+            var properties, _i, properties_3, targetProp, sourceProp, targetType, sourceType;
             return __generator(this, function (_a) {
                 switch (_a.label) {
                     case 0:
                         properties = target.flags & 2097152 /* Intersection */ ? getPropertiesOfUnionOrIntersectionType(target) : getPropertiesOfObjectType(target);
-                        _i = 0, properties_4 = properties;
+                        _i = 0, properties_3 = properties;
                         _a.label = 1;
                     case 1:
-                        if (!(_i < properties_4.length)) return [3 /*break*/, 6];
-                        targetProp = properties_4[_i];
+                        if (!(_i < properties_3.length)) return [3 /*break*/, 6];
+                        targetProp = properties_3[_i];
                         if (!(requireOptionalProperties || !(targetProp.flags & 16777216 /* Optional */))) return [3 /*break*/, 5];
                         sourceProp = getPropertyOfType(source, targetProp.escapedName);
                         if (!!sourceProp) return [3 /*break*/, 3];
@@ -44679,7 +44670,7 @@ var ts;
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
+                    if (ts.getObjectFlags(source) & 524288 /* NonInferrableType */ || source === silentNeverType || (priority & 8 /* ReturnType */ && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     var inference = getInferenceInfoForType(target);
@@ -44779,24 +44770,40 @@ var ts;
                     inferFromTypes(source, target.falseType);
                 }
                 else if (target.flags & 3145728 /* UnionOrIntersection */) {
+                    // We infer from types that are not naked type variables first so that inferences we
+                    // make from nested naked type variables and given slightly higher priority by virtue
+                    // of being first in the candidates array.
+                    var typeVariableCount = 0;
                     for (var _d = 0, _e = target.types; _d < _e.length; _d++) {
                         var t = _e[_d];
-                        var savePriority = priority;
-                        // Inferences directly to naked type variables are given lower priority as they are
-                        // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
-                        // we want to infer string for T, not Promise<string> | string.
                         if (getInferenceInfoForType(t)) {
-                            priority |= 1 /* NakedTypeVariable */;
+                            typeVariableCount++;
+                        }
+                        else {
+                            inferFromTypes(source, t);
+                        }
+                    }
+                    // Inferences directly to naked type variables are given lower priority as they are
+                    // less specific. For example, when inferring from Promise<string> to T | Promise<T>,
+                    // we want to infer string for T, not Promise<string> | string. For intersection types
+                    // we only infer to single naked type variables.
+                    if (target.flags & 1048576 /* Union */ ? typeVariableCount !== 0 : typeVariableCount === 1) {
+                        var savePriority = priority;
+                        priority |= 1 /* NakedTypeVariable */;
+                        for (var _f = 0, _g = target.types; _f < _g.length; _f++) {
+                            var t = _g[_f];
+                            if (getInferenceInfoForType(t)) {
+                                inferFromTypes(source, t);
+                            }
                         }
-                        inferFromTypes(source, t);
                         priority = savePriority;
                     }
                 }
                 else if (source.flags & 1048576 /* Union */) {
                     // Source is a union or intersection type, infer from each constituent type
                     var sourceTypes = source.types;
-                    for (var _f = 0, sourceTypes_3 = sourceTypes; _f < sourceTypes_3.length; _f++) {
-                        var sourceType = sourceTypes_3[_f];
+                    for (var _h = 0, sourceTypes_3 = sourceTypes; _h < sourceTypes_3.length; _h++) {
+                        var sourceType = sourceTypes_3[_h];
                         inferFromTypes(sourceType, target);
                     }
                 }
@@ -44975,8 +44982,8 @@ var ts;
                     }
                 }
                 var properties = getPropertiesOfObjectType(target);
-                for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
-                    var targetProp = properties_5[_i];
+                for (var _i = 0, properties_4 = properties; _i < properties_4.length; _i++) {
+                    var targetProp = properties_4[_i];
                     var sourceProp = getPropertyOfType(source, targetProp.escapedName);
                     if (sourceProp) {
                         inferFromTypes(getTypeOfSymbol(sourceProp), getTypeOfSymbol(targetProp));
@@ -44989,7 +44996,7 @@ var ts;
                 var sourceLen = sourceSignatures.length;
                 var targetLen = targetSignatures.length;
                 var len = sourceLen < targetLen ? sourceLen : targetLen;
-                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* ContainsAnyFunctionType */);
+                var skipParameters = !!(ts.getObjectFlags(source) & 524288 /* NonInferrableType */);
                 for (var i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -50149,7 +50156,7 @@ var ts;
                 spanArray = ts.createNodeArray(args);
                 if (hasSpreadArgument && argCount) {
                     var nextArg = ts.elementAt(args, getSpreadArgumentIndex(args) + 1) || undefined;
-                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : max));
+                    spanArray = ts.createNodeArray(args.slice(max > argCount && nextArg ? args.indexOf(nextArg) : Math.min(max, args.length - 1)));
                 }
             }
             else {
@@ -50570,7 +50577,7 @@ var ts;
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & 8 /* SkipGenericFunctions */ && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -50993,8 +51000,8 @@ var ts;
             var signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
             if (node.expression.kind === 98 /* SuperKeyword */) {
                 return voidType;
@@ -51733,7 +51740,7 @@ var ts;
                     var returnType = getReturnTypeFromBody(node, checkMode);
                     var returnOnlySignature = createSignature(undefined, undefined, undefined, ts.emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     var returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], ts.emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= 524288 /* ContainsAnyFunctionType */;
+                    returnOnlyType.objectFlags |= 524288 /* NonInferrableType */;
                     return links_1.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;
@@ -52115,8 +52122,8 @@ var ts;
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (var _i = 0, properties_6 = properties; _i < properties_6.length; _i++) {
-                var p = properties_6[_i];
+            for (var _i = 0, properties_5 = properties; _i < properties_5.length; _i++) {
+                var p = properties_5[_i];
                 checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
             }
             return sourceType;
@@ -56474,8 +56481,8 @@ var ts;
             for (var _i = 0, baseTypes_2 = baseTypes; _i < baseTypes_2.length; _i++) {
                 var base = baseTypes_2[_i];
                 var properties = getPropertiesOfType(getTypeWithThisArgument(base, type.thisType));
-                for (var _a = 0, properties_7 = properties; _a < properties_7.length; _a++) {
-                    var prop = properties_7[_a];
+                for (var _a = 0, properties_6 = properties; _a < properties_6.length; _a++) {
+                    var prop = properties_6[_a];
                     var existing = seen.get(prop.escapedName);
                     if (!existing) {
                         seen.set(prop.escapedName, { prop: prop, containingType: base });
@@ -58922,7 +58929,7 @@ var ts;
                 // autoArrayType is used as a marker, so even if global Array type is not defined, it needs to be a unique type
                 autoArrayType = createAnonymousType(undefined, emptySymbols, ts.emptyArray, ts.emptyArray, undefined, undefined);
             }
-            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1);
+            globalReadonlyArrayType = getGlobalTypeOrUndefined("ReadonlyArray", /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = getGlobalTypeOrUndefined("ThisType", /*arity*/ 1);
             if (augmentations) {
@@ -63745,7 +63752,7 @@ var ts;
     function createExpressionForAccessorDeclaration(properties, property, receiver, multiLine) {
         var _a = ts.getAllAccessorDeclarations(properties, property), firstAccessor = _a.firstAccessor, getAccessor = _a.getAccessor, setAccessor = _a.setAccessor;
         if (property === firstAccessor) {
-            var properties_8 = [];
+            var properties_7 = [];
             if (getAccessor) {
                 var getterFunction = ts.createFunctionExpression(getAccessor.modifiers, 
                 /*asteriskToken*/ undefined, 
@@ -63756,7 +63763,7 @@ var ts;
                 ts.setTextRange(getterFunction, getAccessor);
                 ts.setOriginalNode(getterFunction, getAccessor);
                 var getter = ts.createPropertyAssignment("get", getterFunction);
-                properties_8.push(getter);
+                properties_7.push(getter);
             }
             if (setAccessor) {
                 var setterFunction = ts.createFunctionExpression(setAccessor.modifiers, 
@@ -63768,15 +63775,15 @@ var ts;
                 ts.setTextRange(setterFunction, setAccessor);
                 ts.setOriginalNode(setterFunction, setAccessor);
                 var setter = ts.createPropertyAssignment("set", setterFunction);
-                properties_8.push(setter);
+                properties_7.push(setter);
             }
-            properties_8.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
-            properties_8.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("enumerable", ts.createTrue()));
+            properties_7.push(ts.createPropertyAssignment("configurable", ts.createTrue()));
             var expression = ts.setTextRange(ts.createCall(ts.createPropertyAccess(ts.createIdentifier("Object"), "defineProperty"), 
             /*typeArguments*/ undefined, [
                 receiver,
                 createExpressionForPropertyName(property.name),
-                ts.createObjectLiteral(properties_8, multiLine)
+                ts.createObjectLiteral(properties_7, multiLine)
             ]), 
             /*location*/ firstAccessor);
             return ts.aggregateTransformFlags(expression);
@@ -68260,8 +68267,8 @@ var ts;
          * @param receiver The receiver on which each property should be assigned.
          */
         function addInitializedPropertyStatements(statements, properties, receiver) {
-            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
-                var property = properties_9[_i];
+            for (var _i = 0, properties_8 = properties; _i < properties_8.length; _i++) {
+                var property = properties_8[_i];
                 var statement = ts.createExpressionStatement(transformInitializedProperty(property, receiver));
                 ts.setSourceMapRange(statement, ts.moveRangePastModifiers(property));
                 ts.setCommentRange(statement, property);
@@ -68277,8 +68284,8 @@ var ts;
          */
         function generateInitializedPropertyExpressions(properties, receiver) {
             var expressions = [];
-            for (var _i = 0, properties_10 = properties; _i < properties_10.length; _i++) {
-                var property = properties_10[_i];
+            for (var _i = 0, properties_9 = properties; _i < properties_9.length; _i++) {
+                var property = properties_9[_i];
                 var expression = transformInitializedProperty(property, receiver);
                 ts.startOnNewLine(expression);
                 ts.setSourceMapRange(expression, ts.moveRangePastModifiers(property));