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Pick<T, K> and similar mapped types propagate modifiers from T

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This commit is contained in:
Anders Hejlsberg 2016-12-10 10:04:30 -08:00
parent 798d080df1
commit 33b512548e
2 changed files with 16 additions and 9 deletions
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24
src/compiler/checker.ts
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@ -4512,12 +4512,11 @@ namespace ts {
// Resolve upfront such that recursive references see an empty object type.
setStructuredTypeMembers(type, emptySymbols, emptyArray, emptyArray, undefined, undefined);
// In { [P in K]: T }, we refer to P as the type parameter type, K as the constraint type,
// and T as the template type. If K is of the form 'keyof S', the mapped type and S are
// homomorphic and we copy property modifiers from corresponding properties in S.
// and T as the template type.
const typeParameter = getTypeParameterFromMappedType(type);
const constraintType = getConstraintTypeFromMappedType(type);
const homomorphicType = getHomomorphicTypeFromMappedType(type);
const templateType = getTemplateTypeFromMappedType(type);
const modifiersType = getModifiersTypeFromMappedType(type);
const templateReadonly = !!type.declaration.readonlyToken;
const templateOptional = !!type.declaration.questionToken;
// First, if the constraint type is a type parameter, obtain the base constraint. Then,
@ -4536,11 +4535,11 @@ namespace ts {
// Otherwise, for type string create a string index signature.
if (t.flags & TypeFlags.StringLiteral) {
const propName = (<LiteralType>t).text;
const homomorphicProp = homomorphicType && getPropertyOfType(homomorphicType, propName);
const isOptional = templateOptional || !!(homomorphicProp && homomorphicProp.flags & SymbolFlags.Optional);
const modifiersProp = getPropertyOfType(modifiersType, propName);
const isOptional = templateOptional || !!(modifiersProp && modifiersProp.flags & SymbolFlags.Optional);
const prop = <TransientSymbol>createSymbol(SymbolFlags.Property | SymbolFlags.Transient | (isOptional ? SymbolFlags.Optional : 0), propName);
prop.type = propType;
prop.isReadonly = templateReadonly || homomorphicProp && isReadonlySymbol(homomorphicProp);
prop.isReadonly = templateReadonly || modifiersProp && isReadonlySymbol(modifiersProp);
members[propName] = prop;
}
else if (t.flags & TypeFlags.String) {
@ -4567,9 +4566,16 @@ namespace ts {
unknownType);
}
function getHomomorphicTypeFromMappedType(type: MappedType) {
const constraint = getConstraintDeclaration(getTypeParameterFromMappedType(type));
return constraint.kind === SyntaxKind.TypeOperator ? instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraint).type), type.mapper || identityMapper) : undefined;
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;
}
return type.modifiersType;
}
function getErasedTemplateTypeFromMappedType(type: MappedType) {

1
src/compiler/types.ts
View file

@ -2933,6 +2933,7 @@ namespace ts {
typeParameter?: TypeParameter;
constraintType?: Type;
templateType?: Type;
modifiersType?: Type;
mapper?: TypeMapper; // Instantiation mapper
}