Skip to content

Widen reverse mapped type properties to fix them being treated as EPC-valid sources #62722

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
jakebailey merged 4 commits into from
Dec 5, 2025
+610 −1
Merged

Widen reverse mapped type properties to fix them being treated as EPC-valid sources #62722

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
97a061d
Widen reverse mapped type properties to fix them being treated as EPC…
Andarist Nov 5, 2025
6fd5860
move the fix to `inferReverseMappedTypeWorker`
Andarist Nov 5, 2025
f395121
Merge remote-tracking branch 'origin/main' into fix/widen-reverse-map…
Andarist Dec 3, 2025
e2f42f5
add extra test
Andarist Dec 5, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion src/compiler/checker.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26436,7 +26436,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const templateType = getTemplateTypeFromMappedType(target);
const inference = createInferenceInfo(typeParameter);
inferTypes([inference], sourceType, templateType);
return getTypeFromInference(inference) || unknownType;
return getWidenedType(getTypeFromInference(inference) || unknownType);
}

function inferReverseMappedType(source: Type, target: MappedType, constraint: IndexType): Type | undefined {
Expand Down
181 changes: 181 additions & 0 deletions tests/baselines/reference/reverseMappedTypeInferenceWidening1.symbols
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,181 @@
//// [tests/cases/compiler/reverseMappedTypeInferenceWidening1.ts] ////

=== reverseMappedTypeInferenceWidening1.ts ===
// https://github.com/microsoft/TypeScript/issues/62720

type TypeFunction<ReturnType = unknown> = (...args: any[]) => ReturnType;
>TypeFunction : Symbol(TypeFunction, Decl(reverseMappedTypeInferenceWidening1.ts, 0, 0))
>ReturnType : Symbol(ReturnType, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 18))
>args : Symbol(args, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 43))
>ReturnType : Symbol(ReturnType, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 18))

type Flags = {
>Flags : Symbol(Flags, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 73))

[flagName: string]: {
>flagName : Symbol(flagName, Decl(reverseMappedTypeInferenceWidening1.ts, 4, 3))

type: TypeFunction;
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 4, 23))
>TypeFunction : Symbol(TypeFunction, Decl(reverseMappedTypeInferenceWidening1.ts, 0, 0))

default?: unknown;
>default : Symbol(default, Decl(reverseMappedTypeInferenceWidening1.ts, 5, 23))

};
};
type TypeFlag<Schemas extends Flags> = {
>TypeFlag : Symbol(TypeFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 8, 2))
>Schemas : Symbol(Schemas, Decl(reverseMappedTypeInferenceWidening1.ts, 9, 14))
>Flags : Symbol(Flags, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 73))

[flag in keyof Schemas]: Schemas[flag] extends { type: TypeFunction<infer T> }
>flag : Symbol(flag, Decl(reverseMappedTypeInferenceWidening1.ts, 10, 3))
>Schemas : Symbol(Schemas, Decl(reverseMappedTypeInferenceWidening1.ts, 9, 14))
>Schemas : Symbol(Schemas, Decl(reverseMappedTypeInferenceWidening1.ts, 9, 14))
>flag : Symbol(flag, Decl(reverseMappedTypeInferenceWidening1.ts, 10, 3))
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 10, 50))
>TypeFunction : Symbol(TypeFunction, Decl(reverseMappedTypeInferenceWidening1.ts, 0, 0))
>T : Symbol(T, Decl(reverseMappedTypeInferenceWidening1.ts, 10, 75))

? T
>T : Symbol(T, Decl(reverseMappedTypeInferenceWidening1.ts, 10, 75))

: never;
};

declare function fn1<Options extends Flags>(
>fn1 : Symbol(fn1, Decl(reverseMappedTypeInferenceWidening1.ts, 13, 2))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 15, 21))
>Flags : Symbol(Flags, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 73))

options: Options,
>options : Symbol(options, Decl(reverseMappedTypeInferenceWidening1.ts, 15, 44))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 15, 21))

): TypeFlag<Options>;
>TypeFlag : Symbol(TypeFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 8, 2))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 15, 21))

const result1 = fn1({
>result1 : Symbol(result1, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 5))
>fn1 : Symbol(fn1, Decl(reverseMappedTypeInferenceWidening1.ts, 13, 2))

booleanFlag: { type: Boolean },
>booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 21))
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 20, 16))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

booleanFlagDefault: {
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 20, 33))

type: Boolean,
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 21, 23))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

default: false,
>default : Symbol(default, Decl(reverseMappedTypeInferenceWidening1.ts, 22, 18))

},
});
result1.booleanFlag; // boolean
>result1.booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 21))
>result1 : Symbol(result1, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 5))
>booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 21))

result1.booleanFlagDefault; // boolean
>result1.booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 20, 33))
>result1 : Symbol(result1, Decl(reverseMappedTypeInferenceWidening1.ts, 19, 5))
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 20, 33))

declare function fn2<Options extends Flags>(
>fn2 : Symbol(fn2, Decl(reverseMappedTypeInferenceWidening1.ts, 27, 27))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 29, 21))
>Flags : Symbol(Flags, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 73))

options: Readonly<Options>,
>options : Symbol(options, Decl(reverseMappedTypeInferenceWidening1.ts, 29, 44))
>Readonly : Symbol(Readonly, Decl(lib.es5.d.ts, --, --))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 29, 21))

): TypeFlag<Options>;
>TypeFlag : Symbol(TypeFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 8, 2))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 29, 21))

const result2 = fn2({
>result2 : Symbol(result2, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 5))
>fn2 : Symbol(fn2, Decl(reverseMappedTypeInferenceWidening1.ts, 27, 27))

booleanFlag: { type: Boolean },
>booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 21))
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 34, 16))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

booleanFlagDefault: {
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 34, 33))

type: Boolean,
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 35, 23))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

default: false,
>default : Symbol(default, Decl(reverseMappedTypeInferenceWidening1.ts, 36, 18))

},
});
result2.booleanFlag; // boolean
>result2.booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 21))
>result2 : Symbol(result2, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 5))
>booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 21))

result2.booleanFlagDefault; // boolean
>result2.booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 34, 33))
>result2 : Symbol(result2, Decl(reverseMappedTypeInferenceWidening1.ts, 33, 5))
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 34, 33))

declare function fn3<Options extends Flags>(
>fn3 : Symbol(fn3, Decl(reverseMappedTypeInferenceWidening1.ts, 41, 27))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 43, 21))
>Flags : Symbol(Flags, Decl(reverseMappedTypeInferenceWidening1.ts, 2, 73))

options: Readonly<Options>,
>options : Symbol(options, Decl(reverseMappedTypeInferenceWidening1.ts, 43, 44))
>Readonly : Symbol(Readonly, Decl(lib.es5.d.ts, --, --))
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 43, 21))

): Options;
>Options : Symbol(Options, Decl(reverseMappedTypeInferenceWidening1.ts, 43, 21))

const result3 = fn3({
>result3 : Symbol(result3, Decl(reverseMappedTypeInferenceWidening1.ts, 47, 5))
>fn3 : Symbol(fn3, Decl(reverseMappedTypeInferenceWidening1.ts, 41, 27))

booleanFlag: { type: Boolean },
>booleanFlag : Symbol(booleanFlag, Decl(reverseMappedTypeInferenceWidening1.ts, 47, 21))
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 48, 16))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

booleanFlagDefault: {
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 48, 33))

type: Boolean,
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 49, 23))
>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

default: false, // no cursed EPC failure here
>default : Symbol(default, Decl(reverseMappedTypeInferenceWidening1.ts, 50, 18))

},
});

declare function takeType(arg: { type: unknown }): void;
>takeType : Symbol(takeType, Decl(reverseMappedTypeInferenceWidening1.ts, 53, 3))
>arg : Symbol(arg, Decl(reverseMappedTypeInferenceWidening1.ts, 55, 26))
>type : Symbol(type, Decl(reverseMappedTypeInferenceWidening1.ts, 55, 32))

takeType(result3.booleanFlagDefault);
>takeType : Symbol(takeType, Decl(reverseMappedTypeInferenceWidening1.ts, 53, 3))
>result3.booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 48, 33))
>result3 : Symbol(result3, Decl(reverseMappedTypeInferenceWidening1.ts, 47, 5))
>booleanFlagDefault : Symbol(booleanFlagDefault, Decl(reverseMappedTypeInferenceWidening1.ts, 48, 33))

Loading