Pick<T, K> and similar mapped types propagate modifiers from T
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@ -4512,12 +4512,11 @@ namespace ts {
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// Resolve upfront such that recursive references see an empty object type.
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setStructuredTypeMembers(type, emptySymbols, emptyArray, emptyArray, undefined, undefined);
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// In { [P in K]: T }, we refer to P as the type parameter type, K as the constraint type,
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// and T as the template type. If K is of the form 'keyof S', the mapped type and S are
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// homomorphic and we copy property modifiers from corresponding properties in S.
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// and T as the template type.
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const typeParameter = getTypeParameterFromMappedType(type);
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const constraintType = getConstraintTypeFromMappedType(type);
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const homomorphicType = getHomomorphicTypeFromMappedType(type);
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const templateType = getTemplateTypeFromMappedType(type);
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const modifiersType = getModifiersTypeFromMappedType(type);
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const templateReadonly = !!type.declaration.readonlyToken;
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const templateOptional = !!type.declaration.questionToken;
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// First, if the constraint type is a type parameter, obtain the base constraint. Then,
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@ -4536,11 +4535,11 @@ namespace ts {
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// Otherwise, for type string create a string index signature.
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if (t.flags & TypeFlags.StringLiteral) {
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const propName = (<LiteralType>t).text;
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const homomorphicProp = homomorphicType && getPropertyOfType(homomorphicType, propName);
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const isOptional = templateOptional || !!(homomorphicProp && homomorphicProp.flags & SymbolFlags.Optional);
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const modifiersProp = getPropertyOfType(modifiersType, propName);
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const isOptional = templateOptional || !!(modifiersProp && modifiersProp.flags & SymbolFlags.Optional);
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const prop = <TransientSymbol>createSymbol(SymbolFlags.Property | SymbolFlags.Transient | (isOptional ? SymbolFlags.Optional : 0), propName);
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prop.type = propType;
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prop.isReadonly = templateReadonly || homomorphicProp && isReadonlySymbol(homomorphicProp);
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prop.isReadonly = templateReadonly || modifiersProp && isReadonlySymbol(modifiersProp);
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members[propName] = prop;
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}
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else if (t.flags & TypeFlags.String) {
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@ -4567,9 +4566,16 @@ namespace ts {
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unknownType);
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}
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function getHomomorphicTypeFromMappedType(type: MappedType) {
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const constraint = getConstraintDeclaration(getTypeParameterFromMappedType(type));
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return constraint.kind === SyntaxKind.TypeOperator ? instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraint).type), type.mapper || identityMapper) : undefined;
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function getModifiersTypeFromMappedType(type: MappedType) {
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if (!type.modifiersType) {
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// If the mapped type was declared as { [P in keyof T]: X } or as { [P in K]: X }, where
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// K is constrained to 'K extends keyof T', then we will copy property modifiers from T.
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const declaredType = <MappedType>getTypeFromMappedTypeNode(type.declaration);
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const constraint = getConstraintTypeFromMappedType(declaredType);
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const extendedConstraint = constraint.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>constraint) : constraint;
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type.modifiersType = extendedConstraint.flags & TypeFlags.Index ? instantiateType((<IndexType>extendedConstraint).type, type.mapper || identityMapper) : emptyObjectType;
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}
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return type.modifiersType;
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}
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function getErasedTemplateTypeFromMappedType(type: MappedType) {
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@ -2933,6 +2933,7 @@ namespace ts {
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typeParameter?: TypeParameter;
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constraintType?: Type;
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templateType?: Type;
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modifiersType?: Type;
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mapper?: TypeMapper; // Instantiation mapper
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}
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