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Infer from union combined single signatures #58482

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18 changes: 12 additions & 6 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -25695,10 +25695,16 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
inferToMultipleTypes(source, (target as UnionOrIntersectionType).types, target.flags);
}
else if (source.flags & TypeFlags.Union) {
// Source is a union or intersection type, infer from each constituent type
const sourceTypes = (source as UnionOrIntersectionType).types;
for (const sourceType of sourceTypes) {
inferFromTypes(sourceType, target);
const singleSignature = getSingleCallOrConstructSignature(source);
if (singleSignature) {
inferFromTypes(getOrCreateTypeFromSignature(singleSignature), target);
}
else {
// Source is a union type, infer from each constituent type
const sourceTypes = (source as UnionType).types;
for (const sourceType of sourceTypes) {
inferFromTypes(sourceType, target);
}
}
}
else if (target.flags & TypeFlags.TemplateLiteral) {
Expand Down Expand Up @@ -33946,8 +33952,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}

function getSingleSignature(type: Type, kind: SignatureKind, allowMembers: boolean): Signature | undefined {
if (type.flags & TypeFlags.Object) {
const resolved = resolveStructuredTypeMembers(type as ObjectType);
if (type.flags & TypeFlags.StructuredType) {
const resolved = resolveStructuredTypeMembers(type as StructuredType);
if (allowMembers || resolved.properties.length === 0 && resolved.indexInfos.length === 0) {
if (kind === SignatureKind.Call && resolved.callSignatures.length === 1 && resolved.constructSignatures.length === 0) {
return resolved.callSignatures[0];
Expand Down
29 changes: 29 additions & 0 deletions tests/baselines/reference/inferenceFromUnionCombinedSingleSignature1.symbols
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Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
//// [tests/cases/compiler/inferenceFromUnionCombinedSingleSignature1.ts] ////

=== inferenceFromUnionCombinedSingleSignature1.ts ===
// https://github.com/microsoft/TypeScript/issues/58468

declare const fn: (() => void) | ((a: number) => void);
>fn : Symbol(fn, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 2, 13))
>a : Symbol(a, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 2, 35))

declare const x: number;
>x : Symbol(x, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 4, 13))

declare const y: any;
>y : Symbol(y, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 5, 13))

fn.call(null, x);
>fn.call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
>fn : Symbol(fn, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 2, 13))
>call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
>x : Symbol(x, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 4, 13))

fn.call(null, y);
>fn.call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
>fn : Symbol(fn, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 2, 13))
>call : Symbol(CallableFunction.call, Decl(lib.es5.d.ts, --, --))
>y : Symbol(y, Decl(inferenceFromUnionCombinedSingleSignature1.ts, 5, 13))

export {};

43 changes: 43 additions & 0 deletions tests/baselines/reference/inferenceFromUnionCombinedSingleSignature1.types
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@@ -0,0 +1,43 @@
//// [tests/cases/compiler/inferenceFromUnionCombinedSingleSignature1.ts] ////

=== inferenceFromUnionCombinedSingleSignature1.ts ===
// https://github.com/microsoft/TypeScript/issues/58468

declare const fn: (() => void) | ((a: number) => void);
>fn : (() => void) | ((a: number) => void)
> : ^^^^^^^ ^^^^^^ ^^ ^^^^^ ^
>a : number
> : ^^^^^^

declare const x: number;
>x : number
> : ^^^^^^

declare const y: any;
>y : any

fn.call(null, x);
>fn.call(null, x) : void
> : ^^^^
>fn.call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
> : ^ ^^ ^^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^ ^^^^^ ^^ ^^^^^^
>fn : (() => void) | ((a: number) => void)
> : ^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^
>call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
> : ^ ^^ ^^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^ ^^^^^ ^^ ^^^^^^
>x : number
> : ^^^^^^

fn.call(null, y);
>fn.call(null, y) : void
> : ^^^^
>fn.call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
> : ^ ^^ ^^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^ ^^^^^ ^^ ^^^^^^
>fn : (() => void) | ((a: number) => void)
> : ^^^^^^^^^^^^^^^^^ ^^ ^^^^^^^^^^
>call : <T, A extends any[], R>(this: (this: T, ...args: A) => R, thisArg: T, ...args: A) => R
> : ^ ^^ ^^^^^^^^^^^^^^^^ ^^ ^^ ^^ ^^ ^^^^^ ^^ ^^^^^^
>y : any

export {};

2 changes: 1 addition & 1 deletion tests/baselines/reference/jsDeclarationsGetterSetter.js
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Expand Up @@ -280,5 +280,5 @@ export class L {
set x(value: any);
}
export class M {
set x(value: any);
set x(value: boolean);
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This comes from:

/**
 * @param {number | boolean} v
 */
const mSetter1 = (v) => {}
/**
 * @param {string | boolean} v
 */
const mSetter2 = (v) => {}
export class M {}
Object.defineProperty(M.prototype, "x", {
    set: Math.random() ? mSetter1 : mSetter2
});

This feels like an improvement, those setter functions can be combined safely to a single signature with a boolean parameter

}
4 changes: 2 additions & 2 deletions tests/baselines/reference/neverIntersectionNotCallable.types
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Expand Up @@ -12,8 +12,8 @@ declare const f: { (x: string): number, a: "" } & { a: number }
> : ^^^^^^

f()
>f() : any
> : ^^^
>f() : number
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The function itself is still not callable here but that erroneous call shows a better return type now. This is caused by getSingleSignature handling structured types now (an intersection in this very case)

> : ^^^^^^
>f : never
> : ^^^^^

14 changes: 14 additions & 0 deletions tests/cases/compiler/inferenceFromUnionCombinedSingleSignature1.ts
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@@ -0,0 +1,14 @@
// @strict: true
// @noEmit: true

// https://github.com/microsoft/TypeScript/issues/58468

declare const fn: (() => void) | ((a: number) => void);

declare const x: number;
declare const y: any;

fn.call(null, x);
fn.call(null, y);

export {};