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Add infer T constraint inference rule matching up mapped type templates across check/extends types (#43649)

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Wesley Wigham 2021-04-21 12:49:02 -07:00 committed by GitHub
parent a433c3c0ce
commit 8ea4ec9496
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5 changed files with 110 additions and 0 deletions
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13
src/compiler/checker.ts
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@ -12613,6 +12613,19 @@ namespace ts {
else if (grandParent.kind === SyntaxKind.TypeParameter && grandParent.parent.kind === SyntaxKind.MappedType) {
inferences = append(inferences, keyofConstraintType);
}
// When an 'infer T' declaration is the template of a mapped type, and that mapped type if the extends
// clause of a conditional whose check type is also a mapped type, give it the constraint of the template
// of the check type's mapped type
else if (grandParent.kind === SyntaxKind.MappedType && (grandParent as MappedTypeNode).type &&
skipParentheses((grandParent as MappedTypeNode).type!) === declaration.parent && grandParent.parent.kind === SyntaxKind.ConditionalType &&
(grandParent.parent as ConditionalTypeNode).extendsType === grandParent && (grandParent.parent as ConditionalTypeNode).checkType.kind === SyntaxKind.MappedType &&
((grandParent.parent as ConditionalTypeNode).checkType as MappedTypeNode).type) {
const checkMappedType = (grandParent.parent as ConditionalTypeNode).checkType as MappedTypeNode;
const nodeType = getTypeFromTypeNode(checkMappedType.type!);
inferences = append(inferences, instantiateType(nodeType,
makeUnaryTypeMapper(getDeclaredTypeOfTypeParameter(getSymbolOfNode(checkMappedType.typeParameter)), checkMappedType.typeParameter.constraint ? getTypeFromTypeNode(checkMappedType.typeParameter.constraint) : keyofConstraintType)
));
}
}
}
}

21
tests/baselines/reference/inferConditionalConstraintMappedMember.js Normal file
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@ -0,0 +1,21 @@
//// [inferConditionalConstraintMappedMember.ts]
// Return keyof type without string index signature
type KeysWithoutStringIndex<T> =
{ [K in keyof T]: string extends K ? never : K } extends { [_ in keyof T]: infer U }
? U
: never
// Only "foo" | "bar" as expected, [string] index signature removed
type test = KeysWithoutStringIndex<{ [index: string]: string; foo: string; bar: 'baz' }>
// KeysWithoutStringIndex<T> will always be a subset of keyof T, but is reported as unassignable
export type RemoveIdxSgn<T> = Pick<T, KeysWithoutStringIndex<T>>
// ERROR:
// Type 'KeysWithoutStringIndex<T>' does not satisfy the constraint 'keyof T'.
// Type 'unknown' is not assignable to type 'keyof T'.(2344)
//// [inferConditionalConstraintMappedMember.js]
"use strict";
exports.__esModule = true;
// ERROR:
// Type 'KeysWithoutStringIndex<T>' does not satisfy the constraint 'keyof T'.
// Type 'unknown' is not assignable to type 'keyof T'.(2344)

40
tests/baselines/reference/inferConditionalConstraintMappedMember.symbols Normal file
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@ -0,0 +1,40 @@
=== tests/cases/compiler/inferConditionalConstraintMappedMember.ts ===
// Return keyof type without string index signature
type KeysWithoutStringIndex<T> =
>KeysWithoutStringIndex : Symbol(KeysWithoutStringIndex, Decl(inferConditionalConstraintMappedMember.ts, 0, 0))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 1, 28))
{ [K in keyof T]: string extends K ? never : K } extends { [_ in keyof T]: infer U }
>K : Symbol(K, Decl(inferConditionalConstraintMappedMember.ts, 2, 7))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 1, 28))
>K : Symbol(K, Decl(inferConditionalConstraintMappedMember.ts, 2, 7))
>K : Symbol(K, Decl(inferConditionalConstraintMappedMember.ts, 2, 7))
>_ : Symbol(_, Decl(inferConditionalConstraintMappedMember.ts, 2, 64))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 1, 28))
>U : Symbol(U, Decl(inferConditionalConstraintMappedMember.ts, 2, 84))
? U
>U : Symbol(U, Decl(inferConditionalConstraintMappedMember.ts, 2, 84))
: never
// Only "foo" | "bar" as expected, [string] index signature removed
type test = KeysWithoutStringIndex<{ [index: string]: string; foo: string; bar: 'baz' }>
>test : Symbol(test, Decl(inferConditionalConstraintMappedMember.ts, 4, 11))
>KeysWithoutStringIndex : Symbol(KeysWithoutStringIndex, Decl(inferConditionalConstraintMappedMember.ts, 0, 0))
>index : Symbol(index, Decl(inferConditionalConstraintMappedMember.ts, 7, 38))
>foo : Symbol(foo, Decl(inferConditionalConstraintMappedMember.ts, 7, 61))
>bar : Symbol(bar, Decl(inferConditionalConstraintMappedMember.ts, 7, 74))
// KeysWithoutStringIndex<T> will always be a subset of keyof T, but is reported as unassignable
export type RemoveIdxSgn<T> = Pick<T, KeysWithoutStringIndex<T>>
>RemoveIdxSgn : Symbol(RemoveIdxSgn, Decl(inferConditionalConstraintMappedMember.ts, 7, 88))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 9, 25))
>Pick : Symbol(Pick, Decl(lib.es5.d.ts, --, --))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 9, 25))
>KeysWithoutStringIndex : Symbol(KeysWithoutStringIndex, Decl(inferConditionalConstraintMappedMember.ts, 0, 0))
>T : Symbol(T, Decl(inferConditionalConstraintMappedMember.ts, 9, 25))
// ERROR:
// Type 'KeysWithoutStringIndex<T>' does not satisfy the constraint 'keyof T'.
// Type 'unknown' is not assignable to type 'keyof T'.(2344)

23
tests/baselines/reference/inferConditionalConstraintMappedMember.types Normal file
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@ -0,0 +1,23 @@
=== tests/cases/compiler/inferConditionalConstraintMappedMember.ts ===
// Return keyof type without string index signature
type KeysWithoutStringIndex<T> =
>KeysWithoutStringIndex : KeysWithoutStringIndex<T>
{ [K in keyof T]: string extends K ? never : K } extends { [_ in keyof T]: infer U }
? U
: never
// Only "foo" | "bar" as expected, [string] index signature removed
type test = KeysWithoutStringIndex<{ [index: string]: string; foo: string; bar: 'baz' }>
>test : never
>index : string
>foo : string
>bar : "baz"
// KeysWithoutStringIndex<T> will always be a subset of keyof T, but is reported as unassignable
export type RemoveIdxSgn<T> = Pick<T, KeysWithoutStringIndex<T>>
>RemoveIdxSgn : RemoveIdxSgn<T>
// ERROR:
// Type 'KeysWithoutStringIndex<T>' does not satisfy the constraint 'keyof T'.
// Type 'unknown' is not assignable to type 'keyof T'.(2344)

13
tests/cases/compiler/inferConditionalConstraintMappedMember.ts Normal file
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@ -0,0 +1,13 @@
// Return keyof type without string index signature
type KeysWithoutStringIndex<T> =
{ [K in keyof T]: string extends K ? never : K } extends { [_ in keyof T]: infer U }
? U
: never
// Only "foo" | "bar" as expected, [string] index signature removed
type test = KeysWithoutStringIndex<{ [index: string]: string; foo: string; bar: 'baz' }>
// KeysWithoutStringIndex<T> will always be a subset of keyof T, but is reported as unassignable
export type RemoveIdxSgn<T> = Pick<T, KeysWithoutStringIndex<T>>
// ERROR:
// Type 'KeysWithoutStringIndex<T>' does not satisfy the constraint 'keyof T'.
// Type 'unknown' is not assignable to type 'keyof T'.(2344)