Relax requirements on index signatures to 'any' when a type also contains a string index signature to 'any'

src/compiler/checker.ts

@@ -18948,10 +18948,18 @@ namespace ts {
  return indexTypesIdenticalTo(source, target, kind);
  }
  const targetType = getIndexTypeOfType(target, kind);
- if (!targetType || targetType.flags & TypeFlags.Any && !sourceIsPrimitive && kind === IndexKind.String) {
- // Index signature of type any permits assignment from everything but primitives
+ if (!targetType) {
  return Ternary.True;
  }
+ if (targetType.flags & TypeFlags.Any && !sourceIsPrimitive) {
+ // An index signature of type `any` permits assignment from everything but primitives,
+ // provided that there is also a `string` index signature of type `any`.
+ const stringIndexType = kind === IndexKind.String ? targetType : getIndexTypeOfType(target, IndexKind.String);
+ if (stringIndexType && stringIndexType.flags & TypeFlags.Any) {
+ return Ternary.True;
+ }
+
+ }
  if (isGenericMappedType(source)) {
  // A generic mapped type { [P in K]: T } is related to a type with an index signature
  // { [x: string]: U }, and optionally with an index signature { [x: number]: V },

tests/baselines/reference/objectTypeWithStringAndNumberIndexSignatureToAny.errors.txt

@@ -0,0 +1,145 @@
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(43,5): error TS2322: Type 'Obj' is not assignable to type 'NumberTo<any>'.
+ Index signature is missing in type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(49,5): error TS2739: Type 'StringTo<any>' is missing the following properties from type 'Obj': hello, world
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(50,5): error TS2739: Type 'NumberTo<any>' is missing the following properties from type 'Obj': hello, world
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(51,5): error TS2739: Type 'StringAndNumberTo<any>' is missing the following properties from type 'Obj': hello, world
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(61,5): error TS2322: Type 'Obj' is not assignable to type 'NumberTo<any>'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(65,5): error TS2322: Type 'Obj' is not assignable to type 'StringTo<any> & NumberTo<any>'.
+ Type 'Obj' is not assignable to type 'NumberTo<any>'.
+ Index signature is missing in type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(67,5): error TS2322: Type 'StringTo<any>' is not assignable to type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(68,5): error TS2322: Type 'NumberTo<any>' is not assignable to type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(69,5): error TS2739: Type 'StringTo<any> & NumberTo<any>' is missing the following properties from type 'Obj': hello, world
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(84,5): error TS2322: Type 'Obj' is not assignable to type 'NumberToNumber'.
+ Index signature is missing in type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(88,5): error TS2322: Type 'Obj' is not assignable to type 'StringToAnyNumberToNumber'.
+ Index signature is missing in type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(90,5): error TS2322: Type 'StringTo<any>' is not assignable to type 'Obj'.
+tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts(91,5): error TS2739: Type 'NumberTo<number>' is missing the following properties from type 'Obj': hello, world
+
+
+==== tests/cases/conformance/types/members/objectTypeWithStringAndNumberIndexSignatureToAny.ts (13 errors) ====
+ // When checking compatibility between two types,
+ // TypeScript should not require an index signature if
+ // the target side index signature maps to `any` *and*
+ // the target side has *any* string index signature to `any`.
+ //
+ // So an index signature like in
+ //
+ // { [x: number]: any }
+ //
+ // is still required of a source type, but neither index signature in
+ //
+ // { [x: number]: any, [x: string]: any; }
+ //
+ // should be required; *however*, the number index signature in
+ //
+ // { [x: number]: number, [x: string]: any; }
+ //
+ // should always be required.
+
+ interface StringTo<T> {
+ [x: string]: T;
+ }
+
+ interface NumberTo<T> {
+ [x: number]: T;
+ }
+
+ interface StringAndNumberTo<T> extends StringTo<T>, NumberTo<T> {
+ }
+
+ interface Obj {
+ hello: string;
+ world: number;
+ }
+
+ function f1(sToAny: StringTo<any>, nToAny: NumberTo<any>, bothToAny: StringAndNumberTo<any>, someObj: Obj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+ ~~~~~~
+!!! error TS2322: Type 'Obj' is not assignable to type 'NumberTo<any>'.
+!!! error TS2322: Index signature is missing in type 'Obj'.
+
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+
+ someObj = sToAny;
+ ~~~~~~~
+!!! error TS2739: Type 'StringTo<any>' is missing the following properties from type 'Obj': hello, world
+ someObj = nToAny;
+ ~~~~~~~
+!!! error TS2739: Type 'NumberTo<any>' is missing the following properties from type 'Obj': hello, world
+ someObj = bothToAny;
+ ~~~~~~~
+!!! error TS2739: Type 'StringAndNumberTo<any>' is missing the following properties from type 'Obj': hello, world
+ }
+
+ function f2(sToAny: StringTo<any>, nToAny: NumberTo<any>, bothToAny: StringTo<any> & NumberTo<any>, someObj: Obj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+ ~~~~~~
+!!! error TS2322: Type 'Obj' is not assignable to type 'NumberTo<any>'.
+
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+ ~~~~~~~~~
+!!! error TS2322: Type 'Obj' is not assignable to type 'StringTo<any> & NumberTo<any>'.
+!!! error TS2322: Type 'Obj' is not assignable to type 'NumberTo<any>'.
+!!! error TS2322: Index signature is missing in type 'Obj'.
+
+ someObj = sToAny;
+ ~~~~~~~
+!!! error TS2322: Type 'StringTo<any>' is not assignable to type 'Obj'.
+ someObj = nToAny;
+ ~~~~~~~
+!!! error TS2322: Type 'NumberTo<any>' is not assignable to type 'Obj'.
+ someObj = bothToAny;
+ ~~~~~~~
+!!! error TS2739: Type 'StringTo<any> & NumberTo<any>' is missing the following properties from type 'Obj': hello, world
+ }
+
+ type NumberToNumber = NumberTo<number>;
+
+ interface StringToAnyNumberToNumber extends StringTo<any>, NumberToNumber {
+ }
+
+ function f3(sToAny: StringTo<any>, nToNumber: NumberToNumber, strToAnyNumToNum: StringToAnyNumberToNumber, someObj: Obj) {
+ sToAny = nToNumber;
+ sToAny = strToAnyNumToNum;
+ sToAny = someObj;
+
+ nToNumber = sToAny;
+ nToNumber = strToAnyNumToNum;
+ nToNumber = someObj;
+ ~~~~~~~~~
+!!! error TS2322: Type 'Obj' is not assignable to type 'NumberToNumber'.
+!!! error TS2322: Index signature is missing in type 'Obj'.
+
+ strToAnyNumToNum = sToAny;
+ strToAnyNumToNum = nToNumber;
+ strToAnyNumToNum = someObj;
+ ~~~~~~~~~~~~~~~~
+!!! error TS2322: Type 'Obj' is not assignable to type 'StringToAnyNumberToNumber'.
+!!! error TS2322: Index signature is missing in type 'Obj'.
+
+ someObj = sToAny;
+ ~~~~~~~
+!!! error TS2322: Type 'StringTo<any>' is not assignable to type 'Obj'.
+ someObj = nToNumber;
+ ~~~~~~~
+!!! error TS2739: Type 'NumberTo<number>' is missing the following properties from type 'Obj': hello, world
+ someObj = someObj;
+ }

tests/baselines/reference/objectTypeWithStringAndNumberIndexSignatureToAny.js

@@ -0,0 +1,157 @@
+//// [objectTypeWithStringAndNumberIndexSignatureToAny.ts]
+// When checking compatibility between two types,
+// TypeScript should not require an index signature if
+// the target side index signature maps to `any` *and*
+// the target side has *any* string index signature to `any`.
+//
+// So an index signature like in
+//
+// { [x: number]: any }
+//
+// is still required of a source type, but neither index signature in
+//
+// { [x: number]: any, [x: string]: any; }
+//
+// should be required; *however*, the number index signature in
+//
+// { [x: number]: number, [x: string]: any; }
+//
+// should always be required.
+
+interface StringTo<T> {
+ [x: string]: T;
+}
+
+interface NumberTo<T> {
+ [x: number]: T;
+}
+
+interface StringAndNumberTo<T> extends StringTo<T>, NumberTo<T> {
+}
+
+interface Obj {
+ hello: string;
+ world: number;
+}
+
+function f1(sToAny: StringTo<any>, nToAny: NumberTo<any>, bothToAny: StringAndNumberTo<any>, someObj: Obj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+
+ someObj = sToAny;
+ someObj = nToAny;
+ someObj = bothToAny;
+}
+
+function f2(sToAny: StringTo<any>, nToAny: NumberTo<any>, bothToAny: StringTo<any> & NumberTo<any>, someObj: Obj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+
+ someObj = sToAny;
+ someObj = nToAny;
+ someObj = bothToAny;
+}
+
+type NumberToNumber = NumberTo<number>;
+
+interface StringToAnyNumberToNumber extends StringTo<any>, NumberToNumber {
+}
+
+function f3(sToAny: StringTo<any>, nToNumber: NumberToNumber, strToAnyNumToNum: StringToAnyNumberToNumber, someObj: Obj) {
+ sToAny = nToNumber;
+ sToAny = strToAnyNumToNum;
+ sToAny = someObj;
+
+ nToNumber = sToAny;
+ nToNumber = strToAnyNumToNum;
+ nToNumber = someObj;
+
+ strToAnyNumToNum = sToAny;
+ strToAnyNumToNum = nToNumber;
+ strToAnyNumToNum = someObj;
+
+ someObj = sToAny;
+ someObj = nToNumber;
+ someObj = someObj;
+}
+
+//// [objectTypeWithStringAndNumberIndexSignatureToAny.js]
+"use strict";
+// When checking compatibility between two types,
+// TypeScript should not require an index signature if
+// the target side index signature maps to `any` *and*
+// the target side has *any* string index signature to `any`.
+//
+// So an index signature like in
+//
+// { [x: number]: any }
+//
+// is still required of a source type, but neither index signature in
+//
+// { [x: number]: any, [x: string]: any; }
+//
+// should be required; *however*, the number index signature in
+//
+// { [x: number]: number, [x: string]: any; }
+//
+// should always be required.
+function f1(sToAny, nToAny, bothToAny, someObj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+ someObj = sToAny;
+ someObj = nToAny;
+ someObj = bothToAny;
+}
+function f2(sToAny, nToAny, bothToAny, someObj) {
+ sToAny = nToAny;
+ sToAny = bothToAny;
+ sToAny = someObj;
+ nToAny = sToAny;
+ nToAny = bothToAny;
+ nToAny = someObj;
+ bothToAny = sToAny;
+ bothToAny = nToAny;
+ bothToAny = someObj;
+ someObj = sToAny;
+ someObj = nToAny;
+ someObj = bothToAny;
+}
+function f3(sToAny, nToNumber, strToAnyNumToNum, someObj) {
+ sToAny = nToNumber;
+ sToAny = strToAnyNumToNum;
+ sToAny = someObj;
+ nToNumber = sToAny;
+ nToNumber = strToAnyNumToNum;
+ nToNumber = someObj;
+ strToAnyNumToNum = sToAny;
+ strToAnyNumToNum = nToNumber;
+ strToAnyNumToNum = someObj;
+ someObj = sToAny;
+ someObj = nToNumber;
+ someObj = someObj;
+}