Correctly resolve declared type for late bound property symbols of function expressions

src/compiler/checker.ts

@@ -5526,6 +5526,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return getMergedSymbol(symbol.parent && getLateBoundSymbol(symbol.parent));
     }
 
+    function getFunctionExpressionParentSymbolOrSymbol(symbol: Symbol) {
+        return symbol.valueDeclaration?.kind === SyntaxKind.ArrowFunction || symbol.valueDeclaration?.kind === SyntaxKind.FunctionExpression
+            ? getSymbolOfNode(symbol.valueDeclaration.parent) || symbol
+            : symbol;
+    }
+
     function getAlternativeContainingModules(symbol: Symbol, enclosingDeclaration: Node): Symbol[] {
         const containingFile = getSourceFileOfNode(enclosingDeclaration);
         const id = getNodeId(containingFile);
@@ -11236,11 +11242,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
         }
         if (symbol.parent?.valueDeclaration) {
-            const typeNode = getEffectiveTypeAnnotationNode(symbol.parent.valueDeclaration);
-            if (typeNode) {
-                const annotationSymbol = getPropertyOfType(getTypeFromTypeNode(typeNode), symbol.escapedName);
-                if (annotationSymbol) {
-                    return getNonMissingTypeOfSymbol(annotationSymbol);
+            const possiblyAnnotatedSymbol = getFunctionExpressionParentSymbolOrSymbol(symbol.parent);
+            if (possiblyAnnotatedSymbol.valueDeclaration) {
+                const typeNode = getEffectiveTypeAnnotationNode(possiblyAnnotatedSymbol.valueDeclaration);
+                if (typeNode) {
+                    const annotationSymbol = getPropertyOfType(getTypeFromTypeNode(typeNode), symbol.escapedName);
+                    if (annotationSymbol) {
+                        return getNonMissingTypeOfSymbol(annotationSymbol);
+                    }
                 }
             }
         }
@@ -12932,9 +12941,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     }
                 }
             }
-            const assignments = (symbol.valueDeclaration?.kind === SyntaxKind.ArrowFunction || symbol.valueDeclaration?.kind === SyntaxKind.FunctionExpression) &&
-                    getSymbolOfNode(symbol.valueDeclaration.parent)?.assignmentDeclarationMembers ||
-                symbol.assignmentDeclarationMembers;
+            const assignments = getFunctionExpressionParentSymbolOrSymbol(symbol).assignmentDeclarationMembers;
 
             if (assignments) {
                 const decls = arrayFrom(assignments.values());

tests/baselines/reference/expandoFunctionExpressionsWithDynamicNames2.symbols

@@ -0,0 +1,42 @@
+//// [tests/cases/compiler/expandoFunctionExpressionsWithDynamicNames2.ts] ////
+
+=== expandoFunctionExpressionsWithDynamicNames2.ts ===
+const mySymbol = Symbol();
+>mySymbol : Symbol(mySymbol, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 0, 5))
+>Symbol : Symbol(Symbol, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2019.symbol.d.ts, --, --))
+
+interface Foo {
+>Foo : Symbol(Foo, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 0, 26))
+
+  (): void;
+  [mySymbol]: true;
+>[mySymbol] : Symbol(Foo[mySymbol], Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 2, 11))
+>mySymbol : Symbol(mySymbol, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 0, 5))
+}
+const foo: Foo = () => {};
+>foo : Symbol(foo, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 5, 5), Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 5, 26))
+>Foo : Symbol(Foo, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 0, 26))
+
+foo[mySymbol] = true;
+>foo : Symbol(foo, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 5, 5), Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 5, 26))
+>mySymbol : Symbol(mySymbol, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 0, 5))
+
+interface Bar {
+>Bar : Symbol(Bar, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 6, 21))
+
+  (): void;
+  test: true;
+>test : Symbol(Bar.test, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 9, 11))
+}
+const t = "test" as const;
+>t : Symbol(t, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 12, 5))
+>const : Symbol(const)
+
+const bar: Bar = () => {};
+>bar : Symbol(bar, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 13, 5), Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 13, 26))
+>Bar : Symbol(Bar, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 6, 21))
+
+bar[t] = true;
+>bar : Symbol(bar, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 13, 5), Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 13, 26))
+>t : Symbol(t, Decl(expandoFunctionExpressionsWithDynamicNames2.ts, 12, 5))
+

tests/baselines/reference/expandoFunctionExpressionsWithDynamicNames2.types

@@ -0,0 +1,48 @@
+//// [tests/cases/compiler/expandoFunctionExpressionsWithDynamicNames2.ts] ////
+
+=== expandoFunctionExpressionsWithDynamicNames2.ts ===
+const mySymbol = Symbol();
+>mySymbol : unique symbol
+>Symbol() : unique symbol
+>Symbol : SymbolConstructor
+
+interface Foo {
+  (): void;
+  [mySymbol]: true;
+>[mySymbol] : true
+>mySymbol : unique symbol
+>true : true
+}
+const foo: Foo = () => {};
+>foo : Foo
+>() => {} : { (): void; [mySymbol]: true; }
+
+foo[mySymbol] = true;
+>foo[mySymbol] = true : true
+>foo[mySymbol] : true
+>foo : Foo
+>mySymbol : unique symbol
+>true : true
+
+interface Bar {
+  (): void;
+  test: true;
+>test : true
+>true : true
+}
+const t = "test" as const;
+>t : "test"
+>"test" as const : "test"
+>"test" : "test"
+
+const bar: Bar = () => {};
+>bar : Bar
+>() => {} : { (): void; test: true; }
+
+bar[t] = true;
+>bar[t] = true : true
+>bar[t] : true
+>bar : Bar
+>t : "test"
+>true : true
+

tests/cases/compiler/expandoFunctionExpressionsWithDynamicNames2.ts

@@ -0,0 +1,19 @@
+// @strict: true
+// @lib: esnext
+// @noEmit: true
+
+const mySymbol = Symbol();
+interface Foo {
+  (): void;
+  [mySymbol]: true;
+}
+const foo: Foo = () => {};
+foo[mySymbol] = true;
+
+interface Bar {
+  (): void;
+  test: true;
+}
+const t = "test" as const;
+const bar: Bar = () => {};
+bar[t] = true;