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Merge pull request #27695 from Microsoft/mixedDiscriminantTypes

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Allow non-unit types in union discriminants
This commit is contained in:
Anders Hejlsberg
2018-10-15 13:10:27 -07:00
committed by GitHub
parent c184184713 6cdba6d351
commit 9767522ca0
7 changed files with 775 additions and 7 deletions
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16
src/compiler/checker.ts
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@@ -14233,12 +14233,26 @@ namespace ts {
return undefined;
}
function isDiscriminantType(type: Type): boolean {
if (type.flags & TypeFlags.Union) {
if (type.flags & (TypeFlags.Boolean | TypeFlags.EnumLiteral)) {
return true;
}
let combined = 0;
for (const t of (<UnionType>type).types) combined |= t.flags;
if (combined & TypeFlags.Unit && !(combined & TypeFlags.Instantiable)) {
return true;
}
}
return false;
}
function isDiscriminantProperty(type: Type | undefined, name: __String) {
if (type && type.flags & TypeFlags.Union) {
const prop = getUnionOrIntersectionProperty(<UnionType>type, name);
if (prop && getCheckFlags(prop) & CheckFlags.SyntheticProperty) {
if ((<TransientSymbol>prop).isDiscriminantProperty === undefined) {
(<TransientSymbol>prop).isDiscriminantProperty = !!((<TransientSymbol>prop).checkFlags & CheckFlags.HasNonUniformType) && isLiteralType(getTypeOfSymbol(prop));
(<TransientSymbol>prop).isDiscriminantProperty = !!((<TransientSymbol>prop).checkFlags & CheckFlags.HasNonUniformType) && isDiscriminantType(getTypeOfSymbol(prop));
}
return !!(<TransientSymbol>prop).isDiscriminantProperty;
}