Merge pull request microsoft#8387 from Microsoft/controlFlowDestructuringParameter

Fix control flow analysis for destructuring parameters

Author: ahejlsberg

src/compiler/checker.ts

@@ -7959,7 +7959,7 @@ namespace ts {
             }
             const declaration = localOrExportSymbol.valueDeclaration;
             const defaultsToDeclaredType = !strictNullChecks || type.flags & TypeFlags.Any || !declaration ||
-                declaration.kind === SyntaxKind.Parameter || isInAmbientContext(declaration) ||
+                getRootDeclaration(declaration).kind === SyntaxKind.Parameter || isInAmbientContext(declaration) ||
                 getContainingFunctionOrModule(declaration) !== getContainingFunctionOrModule(node);
             const flowType = getFlowTypeOfReference(node, type, defaultsToDeclaredType ? type : undefinedType);
             if (strictNullChecks && !(type.flags & TypeFlags.Any) && !(getNullableKind(type) & TypeFlags.Undefined) && getNullableKind(flowType) & TypeFlags.Undefined) {

tests/baselines/reference/controlFlowDestructuringParameters.js

@@ -0,0 +1,15 @@
+//// [controlFlowDestructuringParameters.ts]
+// Repro for #8376
+
+
+[{ x: 1 }].map(
+  ({ x }) => x
+);
+
+
+//// [controlFlowDestructuringParameters.js]
+// Repro for #8376
+[{ x: 1 }].map(function (_a) {
+    var x = _a.x;
+    return x;
+});

tests/baselines/reference/controlFlowDestructuringParameters.symbols

@@ -0,0 +1,15 @@
+=== tests/cases/compiler/controlFlowDestructuringParameters.ts ===
+// Repro for #8376
+
+
+[{ x: 1 }].map(
+>[{ x: 1 }].map : Symbol(Array.map, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(controlFlowDestructuringParameters.ts, 3, 2))
+>map : Symbol(Array.map, Decl(lib.d.ts, --, --))
+
+  ({ x }) => x
+>x : Symbol(x, Decl(controlFlowDestructuringParameters.ts, 4, 4))
+>x : Symbol(x, Decl(controlFlowDestructuringParameters.ts, 4, 4))
+
+);
+

tests/baselines/reference/controlFlowDestructuringParameters.types

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/controlFlowDestructuringParameters.ts ===
+// Repro for #8376
+
+
+[{ x: 1 }].map(
+>[{ x: 1 }].map(  ({ x }) => x) : number[]
+>[{ x: 1 }].map : <U>(callbackfn: (value: { x: number; }, index: number, array: { x: number; }[]) => U, thisArg?: any) => U[]
+>[{ x: 1 }] : { x: number; }[]
+>{ x: 1 } : { x: number; }
+>x : number
+>1 : number
+>map : <U>(callbackfn: (value: { x: number; }, index: number, array: { x: number; }[]) => U, thisArg?: any) => U[]
+
+  ({ x }) => x
+>({ x }) => x : ({x}: { x: number; }) => number
+>x : number
+>x : number
+
+);
+

tests/cases/compiler/controlFlowDestructuringParameters.ts

@@ -0,0 +1,7 @@
+// Repro for #8376
+
+// @strictNullChecks: true
+
+[{ x: 1 }].map(
+  ({ x }) => x
+);