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Commit9f33bf1

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TypeScript Botahejlsberg
TypeScript Bot
andauthored
🤖 Pick PR#58098 (Fix constraints of nested homomorph...) into release-5.4 (#58118)
Co-authored-by: Anders Hejlsberg <andersh@microsoft.com>
1 parent71b2f84 commit9f33bf1

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4 files changed

+103
-7
lines changed

4 files changed

+103
-7
lines changed

‎src/compiler/checker.ts‎

Lines changed: 11 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -14552,16 +14552,20 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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return type.resolvedApparentType || (type.resolvedApparentType = getResolvedApparentTypeOfMappedType(type));
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}
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14555-
function getResolvedApparentTypeOfMappedType(type: MappedType) {
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function getResolvedApparentTypeOfMappedType(type: MappedType): Type {
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const target = (type.target ?? type) as MappedType;
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const typeVariable = getHomomorphicTypeVariable(target);
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if (typeVariable && !target.declaration.nameType) {
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const constraint = getConstraintTypeFromMappedType(type);
14560-
if (constraint.flags & TypeFlags.Index) {
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const baseConstraint = getBaseConstraintOfType((constraint as IndexType).type);
14562-
if (baseConstraint && everyType(baseConstraint, t => isArrayOrTupleType(t) || isArrayOrTupleOrIntersection(t))) {
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return instantiateType(target, prependTypeMapping(typeVariable, baseConstraint, type.mapper));
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}
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// We have a homomorphic mapped type or an instantiation of a homomorphic mapped type, i.e. a type
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// of the form { [P in keyof T]: X }. Obtain the modifiers type (the T of the keyof T), and if it is
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// another generic mapped type, recursively obtain its apparent type. Otherwise, obtain its base
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// constraint. Then, if every constituent of the base constraint is an array or tuple type, apply
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// this mapped type to the base constraint. It is safe to recurse when the modifiers type is a
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// mapped type because we protect again circular constraints in getTypeFromMappedTypeNode.
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const modifiersType = getModifiersTypeFromMappedType(type);
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const baseConstraint = isGenericMappedType(modifiersType) ? getApparentTypeOfMappedType(modifiersType) : getBaseConstraintOfType(modifiersType);
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if (baseConstraint && everyType(baseConstraint, t => isArrayOrTupleType(t) || isArrayOrTupleOrIntersection(t))) {
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return instantiateType(target, prependTypeMapping(typeVariable, baseConstraint, type.mapper));
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}
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}
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return type;
Lines changed: 51 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,51 @@
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//// [tests/cases/compiler/homomorphicMappedTypeNesting.ts] ////
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=== homomorphicMappedTypeNesting.ts ===
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// Repro from #58060
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type Box<T extends string> = { v: T };
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>Box : Symbol(Box, Decl(homomorphicMappedTypeNesting.ts, 0, 0))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 2, 9))
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>v : Symbol(v, Decl(homomorphicMappedTypeNesting.ts, 2, 30))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 2, 9))
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type Test<T extends string[]> = T
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>Test : Symbol(Test, Decl(homomorphicMappedTypeNesting.ts, 2, 38))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 4, 10))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 4, 10))
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type UnboxArray<T> = {
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>UnboxArray : Symbol(UnboxArray, Decl(homomorphicMappedTypeNesting.ts, 4, 33))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 6, 16))
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[K in keyof T]: T[K] extends Box<infer R> ? R : never;
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>K : Symbol(K, Decl(homomorphicMappedTypeNesting.ts, 7, 5))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 6, 16))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 6, 16))
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>K : Symbol(K, Decl(homomorphicMappedTypeNesting.ts, 7, 5))
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>Box : Symbol(Box, Decl(homomorphicMappedTypeNesting.ts, 0, 0))
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>R : Symbol(R, Decl(homomorphicMappedTypeNesting.ts, 7, 42))
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>R : Symbol(R, Decl(homomorphicMappedTypeNesting.ts, 7, 42))
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};
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type Identity<T> = { [K in keyof T]: T[K] };
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>Identity : Symbol(Identity, Decl(homomorphicMappedTypeNesting.ts, 8, 2))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 10, 14))
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>K : Symbol(K, Decl(homomorphicMappedTypeNesting.ts, 10, 22))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 10, 14))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 10, 14))
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>K : Symbol(K, Decl(homomorphicMappedTypeNesting.ts, 10, 22))
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declare function fnBad<T extends Array<Box<string>>>(...args: T): Test<Identity<UnboxArray<T>>>;
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>fnBad : Symbol(fnBad, Decl(homomorphicMappedTypeNesting.ts, 10, 44))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 12, 23))
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>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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>Box : Symbol(Box, Decl(homomorphicMappedTypeNesting.ts, 0, 0))
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>args : Symbol(args, Decl(homomorphicMappedTypeNesting.ts, 12, 53))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 12, 23))
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>Test : Symbol(Test, Decl(homomorphicMappedTypeNesting.ts, 2, 38))
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>Identity : Symbol(Identity, Decl(homomorphicMappedTypeNesting.ts, 8, 2))
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>UnboxArray : Symbol(UnboxArray, Decl(homomorphicMappedTypeNesting.ts, 4, 33))
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>T : Symbol(T, Decl(homomorphicMappedTypeNesting.ts, 12, 23))
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Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
1+
//// [tests/cases/compiler/homomorphicMappedTypeNesting.ts] ////
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=== homomorphicMappedTypeNesting.ts ===
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// Repro from #58060
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type Box<T extends string> = { v: T };
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>Box : Box<T>
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>v : T
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type Test<T extends string[]> = T
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>Test : T
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type UnboxArray<T> = {
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>UnboxArray : UnboxArray<T>
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[K in keyof T]: T[K] extends Box<infer R> ? R : never;
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};
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type Identity<T> = { [K in keyof T]: T[K] };
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>Identity : Identity<T>
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declare function fnBad<T extends Array<Box<string>>>(...args: T): Test<Identity<UnboxArray<T>>>;
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>fnBad : <T extends Box<string>[]>(...args: T) => Test<Identity<UnboxArray<T>>>
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>args : T
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Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
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//@strict: true
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//@noEmit: true
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// Repro from #58060
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typeBox<Textendsstring>={v:T};
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typeTest<Textendsstring[]>=T
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typeUnboxArray<T>={
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[KinkeyofT]:T[K]extendsBox<inferR> ?R :never;
12+
};
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typeIdentity<T>={[KinkeyofT]:T[K]};
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declarefunctionfnBad<TextendsArray<Box<string>>>(...args:T):Test<Identity<UnboxArray<T>>>;

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