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Fixed an issue with string mappings over generic intersections not being deferred in conditional types #55856

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Merged
sandersn merged 5 commits into from
Oct 26, 2023
Merged

Fixed an issue with string mappings over generic intersections not being deferred in conditional types #55856

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5c9a5a7
Fixed an issue with string mappings over generic intersections not be…
Andarist Sep 25, 2023
9f56c7f
add extra test cases
Andarist Sep 25, 2023
f063271
Fixed an extra test case
Andarist Sep 27, 2023
a678738
Simplify the fix
Andarist Sep 29, 2023
5d29c23
remove redundant passthrough function
Andarist Sep 29, 2023
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2 changes: 1 addition & 1 deletion src/compiler/checker.ts
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Expand Up @@ -17908,7 +17908,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {

function isPatternLiteralPlaceholderType(type: Type): boolean {
if (type.flags & TypeFlags.Intersection) {
return some((type as IntersectionType).types, t => !!(t.flags & (TypeFlags.Literal | TypeFlags.Null | TypeFlags.Undefined)) || isPatternLiteralPlaceholderType(t));
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@ahejlsberg ahejlsberg Sep 29, 2023

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I think this entire fix can be simplified to simply adding a check that the type isn't generic:

return !isGenericType(type) && some(...);

Generic types should never be classified as placeholders since upon instantiation they may become something completely different.

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@Andarist Andarist Sep 29, 2023

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Oh, that's cool! Thanks for the tip. I was worried that addSpans would fail if I did something like this. It seems that (somewhat confusingly) isGenericIndexType already returns true for an intersection like this so addSpans is covered.

return !isGenericType(type) && some((type as IntersectionType).types, t => !!(t.flags & (TypeFlags.Literal | TypeFlags.Nullable)) || isPatternLiteralPlaceholderType(t));
}
return !!(type.flags & (TypeFlags.Any | TypeFlags.String | TypeFlags.Number | TypeFlags.BigInt)) || isPatternLiteralType(type);
}
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68 changes: 68 additions & 0 deletions tests/baselines/reference/stringMappingDeferralInConditionalTypes.symbols
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@@ -0,0 +1,68 @@
//// [tests/cases/conformance/types/literal/stringMappingDeferralInConditionalTypes.ts] ////

=== stringMappingDeferralInConditionalTypes.ts ===
// https://github.com/microsoft/TypeScript/issues/55847

type A<S> = Lowercase<S & string> extends "foo" ? 1 : 0;
>A : Symbol(A, Decl(stringMappingDeferralInConditionalTypes.ts, 0, 0))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 2, 7))
>Lowercase : Symbol(Lowercase, Decl(lib.es5.d.ts, --, --))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 2, 7))

let x1: A<"foo"> = 1; // ok
>x1 : Symbol(x1, Decl(stringMappingDeferralInConditionalTypes.ts, 3, 3))
>A : Symbol(A, Decl(stringMappingDeferralInConditionalTypes.ts, 0, 0))

type B<S> = Lowercase<S & string> extends `f${string}` ? 1 : 0;
>B : Symbol(B, Decl(stringMappingDeferralInConditionalTypes.ts, 3, 21))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 5, 7))
>Lowercase : Symbol(Lowercase, Decl(lib.es5.d.ts, --, --))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 5, 7))

let x2: B<"foo"> = 1; // ok
>x2 : Symbol(x2, Decl(stringMappingDeferralInConditionalTypes.ts, 6, 3))
>B : Symbol(B, Decl(stringMappingDeferralInConditionalTypes.ts, 3, 21))

type C<S> = Capitalize<Lowercase<S & string>> extends "Foo" ? 1 : 0;
>C : Symbol(C, Decl(stringMappingDeferralInConditionalTypes.ts, 6, 21))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 8, 7))
>Capitalize : Symbol(Capitalize, Decl(lib.es5.d.ts, --, --))
>Lowercase : Symbol(Lowercase, Decl(lib.es5.d.ts, --, --))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 8, 7))

let x3: C<"foo"> = 1; // ok
>x3 : Symbol(x3, Decl(stringMappingDeferralInConditionalTypes.ts, 9, 3))
>C : Symbol(C, Decl(stringMappingDeferralInConditionalTypes.ts, 6, 21))

type D<S extends string> = Capitalize<Lowercase<S>> extends "Foo" ? 1 : 0;
>D : Symbol(D, Decl(stringMappingDeferralInConditionalTypes.ts, 9, 21))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 11, 7))
>Capitalize : Symbol(Capitalize, Decl(lib.es5.d.ts, --, --))
>Lowercase : Symbol(Lowercase, Decl(lib.es5.d.ts, --, --))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 11, 7))

let x4: D<"foo"> = 1; // ok
>x4 : Symbol(x4, Decl(stringMappingDeferralInConditionalTypes.ts, 12, 3))
>D : Symbol(D, Decl(stringMappingDeferralInConditionalTypes.ts, 9, 21))

type E<S> = Lowercase<`f${S & string}` & `${S & string}f`>;
>E : Symbol(E, Decl(stringMappingDeferralInConditionalTypes.ts, 12, 21))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 14, 7))
>Lowercase : Symbol(Lowercase, Decl(lib.es5.d.ts, --, --))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 14, 7))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 14, 7))

type F = E<""> extends "f" ? 1 : 0; // 1
>F : Symbol(F, Decl(stringMappingDeferralInConditionalTypes.ts, 14, 59))
>E : Symbol(E, Decl(stringMappingDeferralInConditionalTypes.ts, 12, 21))

type G<S> = E<S> extends "f" ? 1 : 0;
>G : Symbol(G, Decl(stringMappingDeferralInConditionalTypes.ts, 15, 35))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 16, 7))
>E : Symbol(E, Decl(stringMappingDeferralInConditionalTypes.ts, 12, 21))
>S : Symbol(S, Decl(stringMappingDeferralInConditionalTypes.ts, 16, 7))

let x5: G<""> = 1; // ok
>x5 : Symbol(x5, Decl(stringMappingDeferralInConditionalTypes.ts, 17, 3))
>G : Symbol(G, Decl(stringMappingDeferralInConditionalTypes.ts, 15, 35))

46 changes: 46 additions & 0 deletions tests/baselines/reference/stringMappingDeferralInConditionalTypes.types
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//// [tests/cases/conformance/types/literal/stringMappingDeferralInConditionalTypes.ts] ////

=== stringMappingDeferralInConditionalTypes.ts ===
// https://github.com/microsoft/TypeScript/issues/55847

type A<S> = Lowercase<S & string> extends "foo" ? 1 : 0;
>A : A<S>

let x1: A<"foo"> = 1; // ok
>x1 : 1
>1 : 1

type B<S> = Lowercase<S & string> extends `f${string}` ? 1 : 0;
>B : B<S>

let x2: B<"foo"> = 1; // ok
>x2 : 1
>1 : 1

type C<S> = Capitalize<Lowercase<S & string>> extends "Foo" ? 1 : 0;
>C : C<S>

let x3: C<"foo"> = 1; // ok
>x3 : 1
>1 : 1

type D<S extends string> = Capitalize<Lowercase<S>> extends "Foo" ? 1 : 0;
>D : D<S>

let x4: D<"foo"> = 1; // ok
>x4 : 1
>1 : 1

type E<S> = Lowercase<`f${S & string}` & `${S & string}f`>;
>E : Lowercase<`f${S & string}` & `${S & string}f`>

type F = E<""> extends "f" ? 1 : 0; // 1
>F : 1

type G<S> = E<S> extends "f" ? 1 : 0;
>G : G<S>

let x5: G<""> = 1; // ok
>x5 : 1
>1 : 1

21 changes: 21 additions & 0 deletions tests/cases/conformance/types/literal/stringMappingDeferralInConditionalTypes.ts
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// @strict: true
// @noEmit: true

// https://github.com/microsoft/TypeScript/issues/55847

type A<S> = Lowercase<S & string> extends "foo" ? 1 : 0;
let x1: A<"foo"> = 1; // ok

type B<S> = Lowercase<S & string> extends `f${string}` ? 1 : 0;
let x2: B<"foo"> = 1; // ok

type C<S> = Capitalize<Lowercase<S & string>> extends "Foo" ? 1 : 0;
let x3: C<"foo"> = 1; // ok

type D<S extends string> = Capitalize<Lowercase<S>> extends "Foo" ? 1 : 0;
let x4: D<"foo"> = 1; // ok

type E<S> = Lowercase<`f${S & string}` & `${S & string}f`>;
type F = E<""> extends "f" ? 1 : 0; // 1
type G<S> = E<S> extends "f" ? 1 : 0;
let x5: G<""> = 1; // ok