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

Merge pull request #23794 from Microsoft/fixDiscriminatedContextualType

Browse source 
Fix discriminant checking in contextual types
This commit is contained in:
Anders Hejlsberg 2018-05-22 10:35:29 -07:00 committed by GitHub
parent 9d57903630 acee628a31
commit a5029e3d4e
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
1 changed files with 22 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

24
src/compiler/checker.ts
View file

@ -15307,6 +15307,26 @@ namespace ts {
}
}
// Return true if the given expression is possibly a discriminant value. We limit the kinds of
// expressions we check to those that don't depend on their contextual type in order not to cause
// recursive (and possibly infinite) invocations of getContextualType.
function isPossiblyDiscriminantValue(node: Expression): boolean {
switch (node.kind) {
case SyntaxKind.StringLiteral:
case SyntaxKind.NumericLiteral:
case SyntaxKind.NoSubstitutionTemplateLiteral:
case SyntaxKind.TrueKeyword:
case SyntaxKind.FalseKeyword:
case SyntaxKind.NullKeyword:
case SyntaxKind.Identifier:
return true;
case SyntaxKind.PropertyAccessExpression:
case SyntaxKind.ParenthesizedExpression:
return isPossiblyDiscriminantValue((<PropertyAccessExpression | ParenthesizedExpression>node).expression);
}
return false;
}
// Return the contextual type for a given expression node. During overload resolution, a contextual type may temporarily
// be "pushed" onto a node using the contextualType property.
function getApparentTypeOfContextualType(node: Expression): Type {
@ -15320,8 +15340,8 @@ namespace ts {
propLoop: for (const prop of node.properties) {
if (!prop.symbol) continue;
if (prop.kind !== SyntaxKind.PropertyAssignment) continue;
if (isDiscriminantProperty(contextualType, prop.symbol.escapedName)) {
const discriminatingType = getTypeOfNode(prop.initializer);
if (isPossiblyDiscriminantValue(prop.initializer) && isDiscriminantProperty(contextualType, prop.symbol.escapedName)) {
const discriminatingType = checkExpression(prop.initializer);
for (const type of (contextualType as UnionType).types) {
const targetType = getTypeOfPropertyOfType(type, prop.symbol.escapedName);
if (targetType && checkTypeAssignableTo(discriminatingType, targetType, /*errorNode*/ undefined)) {