fix(core): generic inference for signal inputs may break with `--stri…

…ctFunctionTypes` (angular#54652)

This commit fixes that the generic inference for signal inputs may break
with `--strictFunctionTypes`.

We are not using --strictFunctionTypes` in all tests, so function parameters are always
checked bivariantly- while in 1P function parameters are checked contravariantly. This
breaks sub-typing and e.g. `InputSignal<number>` is not a subtype of `InputSignalWithTransform<unknown, number>`.

Root cause is that the input signal captures the equality function that
is exclusively concerned with the `ReadT`. And `ReadT` is never equal, or a
supertype of unknown.

https://www.typescriptlang.org/play?#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-H3G6PZ5vL40KYJZhg59DeOS4tQxBw5hI9HYz2XQaJS2yQWi9YS1xNY9o7r9ZKU2gnc0AEwzDTZVgAUSaABF7wAFe8ZF8ZXJZDJwAAGhSFFwMByNgMAAGKEuBCCxGKfb-nA6C0JglArqugpaEAA

PR Close angular#54652

packages/compiler-cli/src/ngtsc/testing/fake_core/index.ts

@@ -189,7 +189,7 @@ export interface InputFunction {
 export const input: InputFunction = null!;
 
 export type ɵUnwrapInputSignalWriteType<Field> =
-    Field extends InputSignalWithTransform<unknown, infer WriteT>? WriteT : never;
+    Field extends InputSignalWithTransform<any, infer WriteT>? WriteT : never;
 export type ɵUnwrapDirectiveSignalInputs<Dir, Fields extends keyof Dir> = {
   [P in Fields]: ɵUnwrapInputSignalWriteType<Dir[P]>
 };

packages/compiler-cli/src/ngtsc/typecheck/test/test_case_helper.ts

@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import ts from 'typescript';
+
 import {TypeCheckingConfig} from '../api';
 import {diagnose} from '../testing';
 
@@ -54,7 +56,7 @@ export interface TestCase {
  * Diagnoses the given test case, by constructing the test TypeScript file
  * and running the type checker on it.
  */
-export function typeCheckDiagnose(c: TestCase) {
+export function typeCheckDiagnose(c: TestCase, compilerOptions?: ts.CompilerOptions) {
   const inputs = c.inputs ?? {};
   const outputs = c.outputs ?? {};
 
@@ -124,7 +126,7 @@ export function typeCheckDiagnose(c: TestCase) {
                                      .map(([name]) => name),
         },
       ],
-      undefined, c.options);
+      undefined, c.options, compilerOptions);
 
   expect(messages).toEqual(c.expected);
 }
@@ -136,4 +138,12 @@ export function generateDiagnoseJasmineSpecs(cases: TestCase[]): void {
       typeCheckDiagnose(c);
     });
   }
+
+  describe('with `--strict`', () => {
+    for (const c of cases) {
+      (c.focus ? fit : it)(c.id, () => {
+        typeCheckDiagnose(c, {strict: true});
+      });
+    }
+  });
 }

packages/core/src/authoring/input/input_type_checking.ts

@@ -10,7 +10,7 @@ import {InputSignalWithTransform} from './input_signal';
 
 /** Retrieves the `WriteT` of an `InputSignal` and `InputSignalWithTransform`. */
 export type ɵUnwrapInputSignalWriteType<Field> =
-    Field extends InputSignalWithTransform<unknown, infer WriteT>? WriteT : never;
+    Field extends InputSignalWithTransform<any, infer WriteT>? WriteT : never;
 
 /**
  * Unwraps all `InputSignal`/`InputSignalWithTransform` class fields of