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Capture compatible contextual types for unions containing string literals.

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This commit is contained in:
Daniel Rosenwasser
2015-10-02 15:41:12 -07:00
parent 87f2957e4d
commit f721971063
1 changed files with 24 additions and 1 deletions
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25
src/compiler/checker.ts
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@@ -10103,6 +10103,28 @@ namespace ts {
return getUnionType([type1, type2]);
}
function checkStringLiteralExpression(node: LiteralExpression) {
// TODO (drosen): Do we want to apply the same approach to no-sub template literals?
let contextualType = getContextualType(node);
if (contextualType) {
if (contextualType.flags & TypeFlags.Union) {
for (const type of (<UnionType>contextualType).types) {
if (type.flags & TypeFlags.StringLiteral && (<StringLiteralType>type).text === node.text) {
return contextualType;
}
}
}
else if (contextualType.flags & TypeFlags.StringLiteral && (<StringLiteralType>contextualType).text === node.text) {
// NOTE: This doesn't work because the contextual type of a string literal
// always gets its apparent type.
// Thus you'll always end up with 'String' instead of the literal.
return contextualType;
}
}
return stringType;
}
function checkTemplateExpression(node: TemplateExpression): Type {
// We just want to check each expressions, but we are unconcerned with
// the type of each expression, as any value may be coerced into a string.
@@ -10233,8 +10255,9 @@ namespace ts {
case SyntaxKind.TemplateExpression:
return checkTemplateExpression(<TemplateExpression>node);
case SyntaxKind.StringLiteral:
return checkStringLiteralExpression(<LiteralExpression>node);
case SyntaxKind.NoSubstitutionTemplateLiteral:
return stringType;
return stringType
case SyntaxKind.RegularExpressionLiteral:
return globalRegExpType;
case SyntaxKind.ArrayLiteralExpression: