maxmustermann/TypeScript
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

Only evaluate assigned type when declared type is a union type

Browse source
This commit is contained in:
Anders Hejlsberg 2016-04-18 16:37:58 -07:00
parent b5104cbe69
commit 87f55fa683
1 changed files with 10 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

14
src/compiler/checker.ts
View file

@ -7343,9 +7343,9 @@ namespace ts {
// Remove those constituent types of declaredType to which no constituent type of assignedType is assignable.
// For example, when a variable of type number | string | boolean is assigned a value of type number | boolean,
// we remove type string.
function getAssignmentReducedType(declaredType: Type, assignedType: Type) {
function getAssignmentReducedType(declaredType: UnionType, assignedType: Type) {
if (declaredType !== assignedType && declaredType.flags & TypeFlags.Union) {
const reducedTypes = filter((<UnionType>declaredType).types, t => typeMaybeAssignableTo(assignedType, t));
const reducedTypes = filter(declaredType.types, t => typeMaybeAssignableTo(assignedType, t));
if (reducedTypes.length) {
return reducedTypes.length === 1 ? reducedTypes[0] : getUnionType(reducedTypes);
}
@ -7573,16 +7573,22 @@ namespace ts {
function getTypeAtFlowAssignment(flow: FlowAssignment) {
const node = flow.node;
// Assignments only narrow the computed type if the declared type is a union type. Thus, we
// only need to evaluate the assigned type if the declared type is a union type.
if ((node.kind === SyntaxKind.VariableDeclaration || node.kind === SyntaxKind.BindingElement) &&
reference.kind === SyntaxKind.Identifier &&
getResolvedSymbol(<Identifier>reference) === getSymbolOfNode(node)) {
return getAssignmentReducedType(declaredType, getInitialType(<VariableDeclaration | BindingElement>node));
return declaredType.flags & TypeFlags.Union ?
getAssignmentReducedType(<UnionType>declaredType, getInitialType(<VariableDeclaration | BindingElement>node)) :
declaredType;
}
// If the node is not a variable declaration or binding element, it is an identifier
// or a dotted name that is the target of an assignment. If we have a match, reduce
// the declared type by the assigned type.
if (isMatchingReference(reference, node)) {
return getAssignmentReducedType(declaredType, getAssignedType(<Expression>node));
return declaredType.flags & TypeFlags.Union ?
getAssignmentReducedType(<UnionType>declaredType, getAssignedType(<Expression>node)) :
declaredType;
}
// We didn't have a direct match. However, if the reference is a dotted name, this
// may be an assignment to a left hand part of the reference. For example, for a