refactor: simplify/improve effect types

I will refer to all of `create(Computed|RenderEffect|Effect|Memo)` as `createEffect` for brevity.
- Simplified `createEffect` such that it no longer needs the use of rest params.
- Added test cases for effect functions failing partial generic inference (not supported by typescript)

packages/solid/src/reactive/signal.ts

@@ -213,16 +213,16 @@ export type EffectFunction<Prev, Next extends Prev = Prev> = (v: Prev) => Next;
  *
  * @description https://www.solidjs.com/docs/latest/api#createcomputed
  */
+export function createComputed<Next>(
+  fn: EffectFunction<undefined | NoInfer<Next>, Next>,
+  value?: undefined,
+  options?: EffectOptions
+): void;
 export function createComputed<Next, Init = Next>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
   options?: EffectOptions
 ): void;
-export function createComputed<Next, Init = undefined>(
-  ..._: undefined extends Init
-    ? [fn: EffectFunction<Init | Next, Next>, value?: Init, options?: EffectOptions]
-    : [fn: EffectFunction<Init | Next, Next>, value: Init, options?: EffectOptions]
-): void;
 export function createComputed<Next, Init>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
@@ -248,16 +248,16 @@ export function createComputed<Next, Init>(
  *
  * @description https://www.solidjs.com/docs/latest/api#createrendereffect
  */
+export function createRenderEffect<Next>(
+  fn: EffectFunction<undefined | NoInfer<Next>, Next>,
+  value?: undefined,
+  options?: EffectOptions
+): void;
 export function createRenderEffect<Next, Init = Next>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
   options?: EffectOptions
 ): void;
-export function createRenderEffect<Next, Init = undefined>(
-  ..._: undefined extends Init
-    ? [fn: EffectFunction<Init | Next, Next>, value?: Init, options?: EffectOptions]
-    : [fn: EffectFunction<Init | Next, Next>, value: Init, options?: EffectOptions]
-): void;
 export function createRenderEffect<Next, Init>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
@@ -283,17 +283,17 @@ export function createRenderEffect<Next, Init>(
  *
  * @description https://www.solidjs.com/docs/latest/api#createeffect
  */
+export function createEffect<Next>(
+  fn: EffectFunction<undefined | NoInfer<Next>, Next>,
+  value?: undefined,
+  options?: EffectOptions
+): void;
 export function createEffect<Next, Init = Next>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
   options?: EffectOptions
 ): void;
-export function createEffect<Next, Init = undefined>(
-  ..._: undefined extends Init
-    ? [fn: EffectFunction<Init | Next, Next>, value?: Init, options?: EffectOptions]
-    : [fn: EffectFunction<Init | Next, Next>, value: Init, options?: EffectOptions]
-): void;
-export function createEffect<Next, Init = Next>(
+export function createEffect<Next, Init>(
   fn: EffectFunction<Init | Next, Next>,
   value: Init,
   options?: EffectOptions
@@ -366,16 +366,16 @@ export interface MemoOptions<T> extends EffectOptions {
 // The extra _Next generic parameter separates inference of the effect input
 // parameter type from inference of the effect return type, so that the effect
 // return type is always used as the memo Accessor's return type.
+export function createMemo<Next extends _Next, _Next = Next>(
+  fn: EffectFunction<undefined | NoInfer<_Next>, Next>,
+  value?: undefined,
+  options?: MemoOptions<Next>
+): Accessor<Next>;
 export function createMemo<Next extends _Next, Init = Next, _Next = Next>(
   fn: EffectFunction<Init | _Next, Next>,
   value: Init,
   options?: MemoOptions<Next>
 ): Accessor<Next>;
-export function createMemo<Next extends _Next, Init = undefined, _Next = Next>(
-  ..._: undefined extends Init
-    ? [fn: EffectFunction<Init | _Next, Next>, value?: Init, options?: MemoOptions<Next>]
-    : [fn: EffectFunction<Init | _Next, Next>, value: Init, options?: MemoOptions<Next>]
-): Accessor<Next>;
 export function createMemo<Next extends _Next, Init, _Next>(
   fn: EffectFunction<Init | _Next, Next>,
   value: Init,

packages/solid/test/signals.type-tests.ts

@@ -580,6 +580,7 @@ const m2: Accessor<number | undefined> = createMemo(() => 123);
 const m3: //
 Accessor<undefined> = createMemo(() => {});
 const m4: Accessor<void> = createMemo(() => {});
+// @ts-expect-error memo type is determined by the return type, not parameters
 const m5: Accessor<number | undefined> = createMemo(
   // @ts-expect-error void can't be assigned to anything!
   (v?: number) => {}
@@ -602,6 +603,7 @@ const m11: Accessor<number | undefined> = createMemo<number | undefined>(
   v => {},
   123
 );
+// @ts-expect-error memo type is determined by the return type, not parameters
 const m12: Accessor<number | undefined> = createMemo(
   // @ts-expect-error void can't be assigned to anything!
   (v?: number) => {},
@@ -625,7 +627,6 @@ const m18: Accessor<number> =
 const m19: Accessor<number> =
   // @ts-expect-error undefined initial value is not assignable to the number parameter
   createMemo((v: number | string): number => 123);
-// @ts-expect-error because the number return cannot be assigned to the boolean|string parameter
 const m20: Accessor<number> =
   // @ts-expect-error because the number return cannot be assigned to the boolean|string parameter
   createMemo((v: boolean | string): number => 123);
@@ -919,3 +920,13 @@ createRenderEffect<number | boolean>(
     // @ts-expect-error string return is not assignable to number|boolean
     "foo"
 );
+
+// FIXME cases failing due to partial generic inference not being implemented
+// @ts-expect-error second generic is not inferred and remains as number
+const a7: Accessor<number> = createMemo<number>((v: number | string) => 123, "asd");
+// @ts-expect-error second generic is not inferred and remains as number
+createEffect<number>((v: number | string) => 123, "asd");
+// @ts-expect-error second generic is not inferred and remains as number
+createComputed<number>((v: number | string) => 123, "asd");
+// @ts-expect-error second generic is not inferred and remains as number
+createRenderEffect<number>((v: number | string) => 123, "asd");