Merge pull request #29192 from Microsoft/initializerWidening

Fix initializer widening

Author: ahejlsberg

src/compiler/checker.ts

@@ -4919,7 +4919,7 @@ namespace ts {
             if (strictNullChecks && declaration.initializer && !(getFalsyFlags(checkDeclarationInitializer(declaration)) & TypeFlags.Undefined)) {
                 type = getTypeWithFacts(type, TypeFacts.NEUndefined);
             }
-            return declaration.initializer && !getContextualTypeForVariableLikeDeclaration(walkUpBindingElementsAndPatterns(declaration)) ?
+            return declaration.initializer && !getEffectiveTypeAnnotationNode(walkUpBindingElementsAndPatterns(declaration)) ?
                 getUnionType([type, checkDeclarationInitializer(declaration)], UnionReduction.Subtype) :
                 type;
         }
@@ -22810,7 +22810,8 @@ namespace ts {
             const type = getTypeOfExpression(initializer, /*cache*/ true);
             const widened = getCombinedNodeFlags(declaration) & NodeFlags.Const ||
                 isDeclarationReadonly(declaration) ||
-                isTypeAssertion(initializer) ? type : getWidenedLiteralType(type);
+                isTypeAssertion(initializer) ||
+                isLiteralOfContextualType(type, getContextualType(initializer)) ? type : getWidenedLiteralType(type);
             if (isInJSFile(declaration)) {
                 if (widened.flags & TypeFlags.Nullable) {
                     reportImplicitAny(declaration, anyType);

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment3.types

@@ -45,8 +45,8 @@ const [f, g = f, h = i, i = f] = [1]; // error for h = i
 >c : number
 >d : number
 >c : number
->e : number
->e : number
+>e : any
+>e : any
 
 })([1]);
 >[1] : number[]

tests/baselines/reference/destructuringInitializerContextualTypeFromContext.js

@@ -17,9 +17,16 @@ const Child: SFC<Props> = ({
     children,
     name = "Artemis",
     ...props
-}) => `name: ${name} props: ${JSON.stringify(props)}`;
+}) => `name: ${name} props: ${JSON.stringify(props)}`;
+
+// Repro from #29189
+
+declare function f(g: (as: string[]) => void): void
+f(([_1, _2 = undefined]) => undefined)
+
 
 //// [destructuringInitializerContextualTypeFromContext.js]
+"use strict";
 var __assign = (this && this.__assign) || function () {
     __assign = Object.assign || function(t) {
         for (var s, i = 1, n = arguments.length; i < n; i++) {
@@ -48,3 +55,7 @@ var Child = function (_a) {
     var children = _a.children, _b = _a.name, name = _b === void 0 ? "Artemis" : _b, props = __rest(_a, ["children", "name"]);
     return "name: " + name + " props: " + JSON.stringify(props);
 };
+f(function (_a) {
+    var _1 = _a[0], _b = _a[1], _2 = _b === void 0 ? undefined : _b;
+    return undefined;
+});

tests/baselines/reference/destructuringInitializerContextualTypeFromContext.symbols

@@ -56,3 +56,17 @@ const Child: SFC<Props> = ({
 >stringify : Symbol(JSON.stringify, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 >props : Symbol(props, Decl(destructuringInitializerContextualTypeFromContext.ts, 16, 21))
 
+// Repro from #29189
+
+declare function f(g: (as: string[]) => void): void
+>f : Symbol(f, Decl(destructuringInitializerContextualTypeFromContext.ts, 18, 54))
+>g : Symbol(g, Decl(destructuringInitializerContextualTypeFromContext.ts, 22, 19))
+>as : Symbol(as, Decl(destructuringInitializerContextualTypeFromContext.ts, 22, 23))
+
+f(([_1, _2 = undefined]) => undefined)
+>f : Symbol(f, Decl(destructuringInitializerContextualTypeFromContext.ts, 18, 54))
+>_1 : Symbol(_1, Decl(destructuringInitializerContextualTypeFromContext.ts, 23, 4))
+>_2 : Symbol(_2, Decl(destructuringInitializerContextualTypeFromContext.ts, 23, 7))
+>undefined : Symbol(undefined)
+>undefined : Symbol(undefined)
+

tests/baselines/reference/destructuringInitializerContextualTypeFromContext.types

@@ -50,8 +50,24 @@ const Child: SFC<Props> = ({
 >`name: ${name} props: ${JSON.stringify(props)}` : string
 >name : "Apollo" | "Artemis" | "Dionysus" | "Persephone"
 >JSON.stringify(props) : string
->JSON.stringify : { (value: any, replacer?: (key: string, value: any) => any, space?: string | number): string; (value: any, replacer?: (string | number)[], space?: string | number): string; }
+>JSON.stringify : { (value: any, replacer?: ((key: string, value: any) => any) | undefined, space?: string | number | undefined): string; (value: any, replacer?: (string | number)[] | null | undefined, space?: string | number | undefined): string; }
 >JSON : JSON
->stringify : { (value: any, replacer?: (key: string, value: any) => any, space?: string | number): string; (value: any, replacer?: (string | number)[], space?: string | number): string; }
+>stringify : { (value: any, replacer?: ((key: string, value: any) => any) | undefined, space?: string | number | undefined): string; (value: any, replacer?: (string | number)[] | null | undefined, space?: string | number | undefined): string; }
 >props : {}
 
+// Repro from #29189
+
+declare function f(g: (as: string[]) => void): void
+>f : (g: (as: string[]) => void) => void
+>g : (as: string[]) => void
+>as : string[]
+
+f(([_1, _2 = undefined]) => undefined)
+>f(([_1, _2 = undefined]) => undefined) : void
+>f : (g: (as: string[]) => void) => void
+>([_1, _2 = undefined]) => undefined : ([_1, _2]: string[]) => undefined
+>_1 : string
+>_2 : string | undefined
+>undefined : undefined
+>undefined : undefined
+

tests/cases/compiler/destructuringInitializerContextualTypeFromContext.ts

@@ -1,3 +1,5 @@
+// @strict: true
+
 interface SFC<P = {}> {
     (props: P & { children?: any }): any | null;
 }
@@ -16,4 +18,9 @@ const Child: SFC<Props> = ({
     children,
     name = "Artemis",
     ...props
-}) => `name: ${name} props: ${JSON.stringify(props)}`;
+}) => `name: ${name} props: ${JSON.stringify(props)}`;
+
+// Repro from #29189
+
+declare function f(g: (as: string[]) => void): void
+f(([_1, _2 = undefined]) => undefined)