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Discriminant must include at least one unit type and no instantiable types

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This commit is contained in:
Anders Hejlsberg 2018-10-10 15:11:35 -07:00
parent d0698751ce
commit c110f57deb
1 changed files with 15 additions and 5 deletions
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20
src/compiler/checker.ts
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@ -12919,10 +12919,6 @@ namespace ts {
isUnitType(type);
}
function maybeUnitType(type: Type): boolean {
return type.flags & TypeFlags.Union ? some((<UnionType>type).types, isUnitType) : isUnitType(type);
}
function getBaseTypeOfLiteralType(type: Type): Type {
return type.flags & TypeFlags.EnumLiteral ? getBaseTypeOfEnumLiteralType(<LiteralType>type) :
type.flags & TypeFlags.StringLiteral ? stringType :
@ -14216,12 +14212,26 @@ 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) && maybeUnitType(getTypeOfSymbol(prop));
(<TransientSymbol>prop).isDiscriminantProperty = !!((<TransientSymbol>prop).checkFlags & CheckFlags.HasNonUniformType) && isDiscriminantType(getTypeOfSymbol(prop));
}
return !!(<TransientSymbol>prop).isDiscriminantProperty;
}