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Properly discriminate by pattern literal types in isTypeInvalidDueToUnionDiscriminant #61350

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Properly discriminate by pattern literal types in isTypeInvalidDueToUnionDiscriminant #61350

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2 changes: 1 addition & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14453,7 +14453,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
const nameType = property.name && (isJsxNamespacedName(property.name) ? getStringLiteralType(getTextOfJsxAttributeName(property.name)) : getLiteralTypeFromPropertyName(property.name));
const name = nameType && isTypeUsableAsPropertyName(nameType) ? getPropertyNameFromType(nameType) : undefined;
const expected = name === undefined ? undefined : getTypeOfPropertyOfType(contextualType, name);
return !!expected && isLiteralType(expected) && !isTypeAssignableTo(getTypeOfNode(property), expected);
return !!expected && (isLiteralType(expected) || isPatternLiteralType(expected)) && !isTypeAssignableTo(getTypeOfNode(property), expected);
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This matches the logic in createUnionOrIntersectionProperty here. This HasLiteralType is required for Discriminant:

TypeScript/src/compiler/types.ts

Line 6074 in c85e626

Discriminant = HasNonUniformType | HasLiteralType,

});
}

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19 changes: 19 additions & 0 deletions tests/cases/fourslash/completionsDiscriminatedUnion2.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
/// <reference path="fourslash.ts" />

// @strict: true

//// type A = {
//// id: `A:${string}`;
//// a: number;
//// };
////
//// type B = {
//// id: `B:${string}`;
//// b: number;
//// };
////
//// function foo<T extends A | B>(item: T): void {}
////
//// foo({ id: "B:", /**/ });

verify.completions({ marker: "", exact: ["b"] });