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Permit type alias variance annotations only for certain object types (#48589)

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* Permit type alias variance annotations only for certain object types

* Accept new baselines
This commit is contained in:
Anders Hejlsberg
2022-04-06 14:04:42 -07:00
committed by GitHub
parent 3fd8a6e443
commit 8f6e626d1c
4 changed files with 54 additions and 16 deletions
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19
src/compiler/checker.ts
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@@ -34795,14 +34795,19 @@ namespace ts {
}
if (node.parent.kind === SyntaxKind.InterfaceDeclaration || node.parent.kind === SyntaxKind.ClassDeclaration || node.parent.kind === SyntaxKind.TypeAliasDeclaration) {
const modifiers = getVarianceModifiers(typeParameter);
if (modifiers === ModifierFlags.In || modifiers === ModifierFlags.Out) {
if (modifiers) {
const symbol = getSymbolOfNode(node.parent);
const source = createMarkerType(symbol, typeParameter, modifiers === ModifierFlags.Out ? markerSubType : markerSuperType);
const target = createMarkerType(symbol, typeParameter, modifiers === ModifierFlags.Out ? markerSuperType : markerSubType);
const saveVarianceTypeParameter = typeParameter;
varianceTypeParameter = typeParameter;
checkTypeAssignableTo(source, target, node, Diagnostics.Type_0_is_not_assignable_to_type_1_as_implied_by_variance_annotation);
varianceTypeParameter = saveVarianceTypeParameter;
if (node.parent.kind === SyntaxKind.TypeAliasDeclaration && !(getObjectFlags(getDeclaredTypeOfSymbol(symbol)) & (ObjectFlags.Anonymous | ObjectFlags.Mapped))) {
error(node, Diagnostics.Variance_annotations_are_only_supported_in_type_aliases_for_object_function_constructor_and_mapped_types);
}
else if (modifiers === ModifierFlags.In || modifiers === ModifierFlags.Out) {
const source = createMarkerType(symbol, typeParameter, modifiers === ModifierFlags.Out ? markerSubType : markerSuperType);
const target = createMarkerType(symbol, typeParameter, modifiers === ModifierFlags.Out ? markerSuperType : markerSubType);
const saveVarianceTypeParameter = typeParameter;
varianceTypeParameter = typeParameter;
checkTypeAssignableTo(source, target, node, Diagnostics.Type_0_is_not_assignable_to_type_1_as_implied_by_variance_annotation);
varianceTypeParameter = saveVarianceTypeParameter;
}
}
}
addLazyDiagnostic(() => checkTypeNameIsReserved(node.name, Diagnostics.Type_parameter_name_cannot_be_0));

4
src/compiler/diagnosticMessages.json
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@@ -2743,6 +2743,10 @@
"category": "Error",
"code": 2636
},
"Variance annotations are only supported in type aliases for object, function, constructor, and mapped types.": {
"category": "Error",
"code": 2637
},
"Cannot augment module '{0}' with value exports because it resolves to a non-module entity.": {
"category": "Error",