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Always report unmeasurable variance for mapped types #49894

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Always report unmeasurable variance for mapped types #49894

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33d819f
Always report unmeasurable variance for mapped types
ahejlsberg Jul 13, 2022
e9b71d0
Accept new baselines
ahejlsberg Jul 13, 2022
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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 @@ -19978,7 +19978,7 @@ namespace ts {
if (modifiersRelated) {
let result: Ternary;
const targetConstraint = getConstraintTypeFromMappedType(target);
const sourceConstraint = instantiateType(getConstraintTypeFromMappedType(source), getCombinedMappedTypeOptionality(source) < 0 ? reportUnmeasurableMapper : reportUnreliableMapper);
const sourceConstraint = instantiateType(getConstraintTypeFromMappedType(source), reportUnmeasurableMapper);
if (result = isRelatedTo(targetConstraint, sourceConstraint, RecursionFlags.Both, reportErrors)) {
const mapper = createTypeMapper([getTypeParameterFromMappedType(source)], [getTypeParameterFromMappedType(target)]);
if (instantiateType(getNameTypeFromMappedType(source), mapper) === instantiateType(getNameTypeFromMappedType(target), mapper)) {
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14 changes: 13 additions & 1 deletion tests/baselines/reference/consistentAliasVsNonAliasRecordBehavior.errors.txt
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Original file line number Diff line number Diff line change
@@ -1,10 +1,14 @@
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(10,5): error TS2741: Property 'a' is missing in type 'Record<string, string>' but required in type 'Record<"a", string>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(14,5): error TS2741: Property 'a' is missing in type 'Record2<string, string>' but required in type 'Record2<"a", string>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(18,5): error TS2741: Property 'a' is missing in type 'Record<string, string>' but required in type 'Record2<"a", string>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(22,5): error TS2741: Property 'a' is missing in type 'Record2<string, string>' but required in type 'Record<"a", string>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(26,5): error TS2741: Property 'a' is missing in type 'Record<string, T>' but required in type 'Record<"a", T>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(30,5): error TS2741: Property 'a' is missing in type 'Record2<string, T>' but required in type 'Record2<"a", T>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(34,5): error TS2741: Property 'a' is missing in type 'Record<string, T>' but required in type 'Record2<"a", T>'.
tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(38,5): error TS2741: Property 'a' is missing in type 'Record2<string, T>' but required in type 'Record<"a", T>'.


==== tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts (4 errors) ====
==== tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts (8 errors) ====
// TODO: FIXME: All the below cases labeled `no error` _should be an error_, and are only prevented from so being
// by incorrect variance-based relationships
// Ref: https://github.com/Microsoft/TypeScript/issues/29698
Expand All @@ -15,10 +19,14 @@ tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(38,5): error TS2

function defaultRecord(x: Record<'a', string>, y: Record<string, string>) {
x = y; // no error, but error expected.
~
!!! error TS2741: Property 'a' is missing in type 'Record<string, string>' but required in type 'Record<"a", string>'.
}

function customRecord(x: Record2<'a', string>, y: Record2<string, string>) {
x = y; // no error, but error expected.
~
!!! error TS2741: Property 'a' is missing in type 'Record2<string, string>' but required in type 'Record2<"a", string>'.
}

function mixed1(x: Record2<'a', string>, y: Record<string, string>) {
Expand All @@ -35,10 +43,14 @@ tests/cases/compiler/consistentAliasVsNonAliasRecordBehavior.ts(38,5): error TS2

function defaultRecord2<T>(x: Record<'a', T>, y: Record<string, T>) {
x = y; // no error, but error expected.
~
!!! error TS2741: Property 'a' is missing in type 'Record<string, T>' but required in type 'Record<"a", T>'.
}

function customRecord2<T>(x: Record2<'a', T>, y: Record2<string, T>) {
x = y; // no error, but error expected.
~
!!! error TS2741: Property 'a' is missing in type 'Record2<string, T>' but required in type 'Record2<"a", T>'.
}

function mixed3<T>(x: Record2<'a', T>, y: Record<string, T>) {
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