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Preserve modifiers in isomorphic mapped types

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This commit is contained in:
Anders Hejlsberg 2016-11-29 12:48:41 -08:00
parent e313fef683
commit f55b3ef87a
1 changed files with 17 additions and 9 deletions
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26
src/compiler/checker.ts
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@ -4497,12 +4497,14 @@ 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.
// and T as the template type. If K is of the form 'keyof S', the mapped type and S are
// isomorphic and we copy property modifiers from corresponding properties in S.
const typeParameter = getTypeParameterFromMappedType(type);
const constraintType = getConstraintTypeFromMappedType(type);
const isomorphicType = getIsomorphicTypeFromMappedType(type);
const templateType = getTemplateTypeFromMappedType(type);
const isReadonly = !!type.declaration.readonlyToken;
const isOptional = !!type.declaration.questionToken;
const templateReadonly = !!type.declaration.readonlyToken;
const templateOptional = !!type.declaration.questionToken;
// First, if the constraint type is a type parameter, obtain the base constraint. Then,
// if the key type is a 'keyof X', obtain 'keyof C' where C is the base constraint of X.
// Finally, iterate over the constituents of the resulting iteration type.
@ -4515,18 +4517,19 @@ namespace ts {
const iterationMapper = createUnaryTypeMapper(typeParameter, t);
const templateMapper = type.mapper ? combineTypeMappers(type.mapper, iterationMapper) : iterationMapper;
const propType = instantiateType(templateType, templateMapper);
// If the current iteration type constituent is a literal type, create a property.
// Otherwise, for type string create a string index signature and for type number
// create a numeric index signature.
if (t.flags & (TypeFlags.StringLiteral | TypeFlags.NumberLiteral | TypeFlags.EnumLiteral)) {
// If the current iteration type constituent is a string literal type, create a property.
// Otherwise, for type string create a string index signature.
if (t.flags & TypeFlags.StringLiteral) {
const propName = (<LiteralType>t).text;
const isomorphicProp = isomorphicType && getPropertyOfType(isomorphicType, propName);
const isOptional = templateOptional || !!(isomorphicProp && isomorphicProp.flags & SymbolFlags.Optional);
const prop = <TransientSymbol>createSymbol(SymbolFlags.Property | SymbolFlags.Transient | (isOptional ? SymbolFlags.Optional : 0), propName);
prop.type = addOptionality(propType, isOptional);
prop.isReadonly = isReadonly;
prop.isReadonly = templateReadonly || isomorphicProp && isReadonlySymbol(isomorphicProp);
members[propName] = prop;
}
else if (t.flags & TypeFlags.String) {
stringIndexInfo = createIndexInfo(propType, isReadonly);
stringIndexInfo = createIndexInfo(propType, templateReadonly);
}
});
setStructuredTypeMembers(type, members, emptyArray, emptyArray, stringIndexInfo, undefined);
@ -4549,6 +4552,11 @@ namespace ts {
unknownType);
}
function getIsomorphicTypeFromMappedType(type: MappedType) {
const constraint = getConstraintDeclaration(getTypeParameterFromMappedType(type));
return constraint.kind === SyntaxKind.TypeOperator ? instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraint).type), type.mapper || identityMapper) : undefined;
}
function getErasedTemplateTypeFromMappedType(type: MappedType) {
return instantiateType(getTemplateTypeFromMappedType(type), createUnaryTypeMapper(getTypeParameterFromMappedType(type), anyType));
}