Filter out non-array types when contextually typing union members

Author: Andarist

src/compiler/checker.ts

@@ -28838,8 +28838,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     // it is the type of the numeric index signature in T. Otherwise, in ES6 and higher, the contextual type is the iterated
     // type of T.
     function getContextualTypeForElementExpression(arrayContextualType: Type | undefined, index: number): Type | undefined {
+        const hasIterable = getGlobalIterableType(/* reportErrors */ false) !== emptyGenericType;
         return arrayContextualType && (
-            getTypeOfPropertyOfContextualType(arrayContextualType, "" + index as __String)
+            getTypeOfPropertyOfContextualType(filterType(arrayContextualType, t => isArrayOrTupleLikeType(t) || !!getIndexTypeOfType(t, numberType) || hasIterable && isTypeAssignableTo(t, createIterableType(anyType))), "" + index as __String)
             || mapType(
                 arrayContextualType,
                 t => getIteratedTypeOrElementType(IterationUse.Element, t, undefinedType, /*errorNode*/ undefined, /*checkAssignability*/ false),

tests/baselines/reference/contextualSignatureInArrayElementPrefersArrayUnionMember.symbols

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/contextualSignatureInArrayElementPrefersArrayUnionMember.ts ===
+// repro from #52588
+
+declare function test(
+>test : Symbol(test, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 0, 0))
+
+  arg: Record<string, (arg: string) => void> | Array<(arg: number) => void>
+>arg : Symbol(arg, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 2, 22))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>arg : Symbol(arg, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 3, 23))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>arg : Symbol(arg, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 3, 54))
+
+): void;
+
+test([
+>test : Symbol(test, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 0, 0))
+
+  (arg) => {
+>arg : Symbol(arg, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 7, 3))
+
+    arg; // number
+>arg : Symbol(arg, Decl(contextualSignatureInArrayElementPrefersArrayUnionMember.ts, 7, 3))
+
+  },
+]);
+

tests/baselines/reference/contextualSignatureInArrayElementPrefersArrayUnionMember.types

@@ -0,0 +1,28 @@
+=== tests/cases/compiler/contextualSignatureInArrayElementPrefersArrayUnionMember.ts ===
+// repro from #52588
+
+declare function test(
+>test : (arg: Record<string, (arg: string) => void> | ((arg: number) => void)[]) => void
+
+  arg: Record<string, (arg: string) => void> | Array<(arg: number) => void>
+>arg : Record<string, (arg: string) => void> | ((arg: number) => void)[]
+>arg : string
+>arg : number
+
+): void;
+
+test([
+>test([  (arg) => {    arg; // number  },]) : void
+>test : (arg: Record<string, (arg: string) => void> | ((arg: number) => void)[]) => void
+>[  (arg) => {    arg; // number  },] : ((arg: number) => void)[]
+
+  (arg) => {
+>(arg) => {    arg; // number  } : (arg: number) => void
+>arg : number
+
+    arg; // number
+>arg : number
+
+  },
+]);
+

tests/cases/compiler/contextualSignatureInArrayElementPrefersArrayUnionMember.ts

@@ -0,0 +1,14 @@
+// @strict: true
+// @noEmit: true
+
+// repro from #52588
+
+declare function test(
+  arg: Record<string, (arg: string) => void> | Array<(arg: number) => void>
+): void;
+
+test([
+  (arg) => {
+    arg; // number
+  },
+]);