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Fix discriminant checking in contextual types to avoid infinite recursion

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This commit is contained in:
Anders Hejlsberg 2018-04-30 15:42:52 -07:00
parent 83bc70dd63
commit acee628a31
1 changed files with 22 additions and 2 deletions
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24
src/compiler/checker.ts
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@ -15036,6 +15036,26 @@ 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 {
@ -15049,8 +15069,8 @@ 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)) {