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Refrain from attempting to perform parameter fixing on a generic signature multiple times #43835

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Merged
merged 2 commits into from
Apr 27, 2021
Merged

Refrain from attempting to perform parameter fixing on a generic signature multiple times #43835

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95a89b2
Refrain from attempting to perform parameter fixing on a generic sign…
weswigham Apr 26, 2021
d849c11
Remove assertion
weswigham Apr 27, 2021
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9 changes: 8 additions & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -30345,7 +30345,14 @@ namespace ts {
}

function assignContextualParameterTypes(signature: Signature, context: Signature) {
signature.typeParameters = context.typeParameters;
if (context.typeParameters) {
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Is context.typeParameters ever undefined? Was that the bug here?

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I mean, I don't want to overwrite a signature's type parameters with undefined, and there's no reason to do anything if they're both undefined.

if (!signature.typeParameters) {
signature.typeParameters = context.typeParameters;
}
else {
return; // This signature has already has a contextual inference performed and cached on it!
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Double-checking my understanding; is this correct?: it's enough to bail after seeing that typeParameters is set, because a normal run of this function sets both typeParameters and parameters. So you don't have to check parameters as well.

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Aye. Moreover, if a function somehow has type parameters set already, but not parameters, fixing parameters which contain a separate set of type parameters would be bad, too. (It'd be like the inverse of the original issue that caused the report)

}
}
if (context.thisParameter) {
const parameter = signature.thisParameter;
if (!parameter || parameter.valueDeclaration && !(<ParameterDeclaration>parameter.valueDeclaration).type) {
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10 changes: 10 additions & 0 deletions tests/baselines/reference/contextuallyTypedGenericAssignment.js
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@@ -0,0 +1,10 @@
//// [contextuallyTypedGenericAssignment.ts]
function foo<A extends any[]>(
arg: <T extends { a: number }>(t: T, ...rest: A) => number
) { }

foo((t, u: number) => t.a)

//// [contextuallyTypedGenericAssignment.js]
function foo(arg) { }
foo(function (t, u) { return t.a; });
24 changes: 24 additions & 0 deletions tests/baselines/reference/contextuallyTypedGenericAssignment.symbols
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@@ -0,0 +1,24 @@
=== tests/cases/compiler/contextuallyTypedGenericAssignment.ts ===
function foo<A extends any[]>(
>foo : Symbol(foo, Decl(contextuallyTypedGenericAssignment.ts, 0, 0))
>A : Symbol(A, Decl(contextuallyTypedGenericAssignment.ts, 0, 13))

arg: <T extends { a: number }>(t: T, ...rest: A) => number
>arg : Symbol(arg, Decl(contextuallyTypedGenericAssignment.ts, 0, 30))
>T : Symbol(T, Decl(contextuallyTypedGenericAssignment.ts, 1, 10))
>a : Symbol(a, Decl(contextuallyTypedGenericAssignment.ts, 1, 21))
>t : Symbol(t, Decl(contextuallyTypedGenericAssignment.ts, 1, 35))
>T : Symbol(T, Decl(contextuallyTypedGenericAssignment.ts, 1, 10))
>rest : Symbol(rest, Decl(contextuallyTypedGenericAssignment.ts, 1, 40))
>A : Symbol(A, Decl(contextuallyTypedGenericAssignment.ts, 0, 13))

) { }

foo((t, u: number) => t.a)
>foo : Symbol(foo, Decl(contextuallyTypedGenericAssignment.ts, 0, 0))
>t : Symbol(t, Decl(contextuallyTypedGenericAssignment.ts, 4, 5))
>u : Symbol(u, Decl(contextuallyTypedGenericAssignment.ts, 4, 7))
>t.a : Symbol(a, Decl(contextuallyTypedGenericAssignment.ts, 1, 21))
>t : Symbol(t, Decl(contextuallyTypedGenericAssignment.ts, 4, 5))
>a : Symbol(a, Decl(contextuallyTypedGenericAssignment.ts, 1, 21))

22 changes: 22 additions & 0 deletions tests/baselines/reference/contextuallyTypedGenericAssignment.types
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@@ -0,0 +1,22 @@
=== tests/cases/compiler/contextuallyTypedGenericAssignment.ts ===
function foo<A extends any[]>(
>foo : <A extends any[]>(arg: <T extends { a: number; }>(t: T, ...rest: A) => number) => void

arg: <T extends { a: number }>(t: T, ...rest: A) => number
>arg : <T extends { a: number; }>(t: T, ...rest: A) => number
>a : number
>t : T
>rest : A

) { }

foo((t, u: number) => t.a)
>foo((t, u: number) => t.a) : void
>foo : <A extends any[]>(arg: <T extends { a: number; }>(t: T, ...rest: A) => number) => void
>(t, u: number) => t.a : <T extends { a: number; }>(t: T, u: number) => number
>t : T
>u : number
>t.a : number
>t : T
>a : number

5 changes: 5 additions & 0 deletions tests/cases/compiler/contextuallyTypedGenericAssignment.ts
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@@ -0,0 +1,5 @@
function foo<A extends any[]>(
arg: <T extends { a: number }>(t: T, ...rest: A) => number
) { }

foo((t, u: number) => t.a)