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Additional tweak to mapped type property modifier propagation

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This commit is contained in:
Anders Hejlsberg
2016-12-11 17:43:46 -08:00
parent 7c5c664a1c
commit 52291762d7
1 changed files with 16 additions and 6 deletions
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22
src/compiler/checker.ts
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@@ -4577,12 +4577,22 @@ namespace ts {
function getModifiersTypeFromMappedType(type: MappedType) {
if (!type.modifiersType) {
// If the mapped type was declared as { [P in keyof T]: X } or as { [P in K]: X }, where
// K is constrained to 'K extends keyof T', then we will copy property modifiers from T.
const declaredType = <MappedType>getTypeFromMappedTypeNode(type.declaration);
const constraint = getConstraintTypeFromMappedType(declaredType);
const extendedConstraint = constraint.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>constraint) : constraint;
type.modifiersType = extendedConstraint.flags & TypeFlags.Index ? instantiateType((<IndexType>extendedConstraint).type, type.mapper || identityMapper) : emptyObjectType;
const constraintDeclaration = type.declaration.typeParameter.constraint;
if (constraintDeclaration.kind === SyntaxKind.TypeOperator) {
// If the constraint declaration is a 'keyof T' node, the modifiers type is T. We check
// AST nodes here because, when T is a non-generic type, the logic below eagerly resolves
// 'keyof T' to a literal union type and we can't recover T from that type.
type.modifiersType = instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraintDeclaration).type), type.mapper || identityMapper);
}
else {
// Otherwise, get the declared constraint type, and if the constraint type is a type parameter,
// get the constraint of that type parameter. If the resulting type is an indexed type 'keyof T',
// the modifiers type is T. Otherwise, the modifiers type is {}.
const declaredType = <MappedType>getTypeFromMappedTypeNode(type.declaration);
const constraint = getConstraintTypeFromMappedType(declaredType);
const extendedConstraint = constraint.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>constraint) : constraint;
type.modifiersType = extendedConstraint.flags & TypeFlags.Index ? instantiateType((<IndexType>extendedConstraint).type, type.mapper || identityMapper) : emptyObjectType;
}
}
return type.modifiersType;
}