ReadonlyDeep/WritableDeep: Fix TypeScript 5.4 compatibility (#839)

package.json

@@ -41,7 +41,7 @@
  "devDependencies": {
  "expect-type": "^0.15.0",
  "npm-run-all2": "^6.1.2",
- "tsd": "^0.29.0",
+ "tsd": "^0.31.0",
  "typescript": "~5.4.3",
  "xo": "^0.58.0"
  },

source/internal.d.ts

@@ -416,9 +416,11 @@ Multiple call signatures cannot currently be supported due to a TypeScript limit
 @see https://github.com/microsoft/TypeScript/issues/29732
 */
 export type HasMultipleCallSignatures<T extends (...arguments_: any[]) => unknown> =
- T extends {(...arguments_: infer A): unknown; (...arguments_: any[]): unknown}
- ? unknown[] extends A
- ? false
+ T extends {(...arguments_: infer A): unknown; (...arguments_: infer B): unknown}
+ ? B extends A
+ ? A extends B
+ ? false
+ : true
  : true
  : false;
 

test-d/internal/has-multiple-call-signatures.ts

@@ -0,0 +1,22 @@
+import {expectType} from 'tsd';
+import type {HasMultipleCallSignatures} from '../../source/internal';
+
+type Overloaded = {
+ (foo: number): string;
+ (foo: string, bar: number): number;
+};
+
+type Overloaded2 = {
+ (foo: number | undefined): string;
+ // eslint-disable-next-line @typescript-eslint/unified-signatures
+ (foo: number): string;
+};
+
+type Namespace = {
+ (foo: number): string;
+ baz: boolean[];
+};
+
+expectType<true>({} as HasMultipleCallSignatures<Overloaded>);
+expectType<true>({} as HasMultipleCallSignatures<Overloaded2>);
+expectType<false>({} as HasMultipleCallSignatures<Namespace>);

test-d/readonly-deep.ts

@@ -123,3 +123,18 @@ type VoidTypeExpected = {
 };
 declare const voidType: ReadonlyDeep<VoidType>;
 expectType<VoidTypeExpected>(voidType);
+
+// Standalone tests
+
+// eslint-disable-next-line @typescript-eslint/consistent-type-assertions
+const readonlyNamespace = {} as ReadonlyDeep<{
+ (foo: number): string;
+ baz: boolean[];
+}>;
+expectType<((foo: number) => string) & {
+ readonly baz: readonly boolean[];
+}>(readonlyNamespace);
+expectAssignable<{
+ (foo: number): string;
+ readonly baz: readonly boolean[];
+}>(readonlyNamespace);

test-d/writable-deep.ts

@@ -121,3 +121,18 @@ const fullyWritableData = {
  },
 };
 expectAssignable<WritableDeep<ReadonlyDeep<typeof fullyWritableData>>>(fullyWritableData);
+
+// Standalone tests
+
+// eslint-disable-next-line @typescript-eslint/consistent-type-assertions
+const writableNamespace = {} as WritableDeep<{
+ (foo: number): string;
+ readonly baz: readonly boolean[];
+}>;
+expectType<((foo: number) => string) & {
+ baz: boolean[];
+}>(writableNamespace);
+expectAssignable<{
+ (foo: number): string;
+ baz: boolean[];
+}>(writableNamespace);

tsconfig.json

@@ -25,9 +25,5 @@
  // "noUncheckedIndexedAccess": true, // TODO: Enable.
  "noPropertyAccessFromIndexSignature": true,
  "useDefineForClassFields": true,
- },
- "exclude": [
- // Ignore `WriteableDeep` error temporarily, remove when #833 are fixed.
- "test-d/writable-deep.ts",
- ]
+ }
 }