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Narrowing doesn't require switch expression to be unit type

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This commit is contained in:
Anders Hejlsberg 2016-07-06 19:50:44 -07:00
parent 5225997c8c
commit 280b27e263
1 changed files with 4 additions and 6 deletions
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10
src/compiler/checker.ts
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@ -6946,12 +6946,12 @@ namespace ts {
}
function isUnitType(type: Type): boolean {
return type.flags & (TypeFlags.Literal | TypeFlags.Void | TypeFlags.Undefined | TypeFlags.Null) ||
return type.flags & (TypeFlags.Literal | TypeFlags.Undefined | TypeFlags.Null) ||
type.flags & TypeFlags.Enum && type.symbol.flags & SymbolFlags.EnumMember ? true : false;
}
function isUnitUnionType(type: Type): boolean {
return type.flags & TypeFlags.Union ? forEach((<UnionType>type).types, isUnitType) : isUnitType(type);
return type.flags & TypeFlags.Union ? !forEach((<UnionType>type).types, t => !isUnitType(t)) : isUnitType(type);
}
function getBaseTypeOfUnitType(type: Type): Type {
@ -8209,9 +8209,7 @@ namespace ts {
}
function narrowTypeBySwitchOnDiscriminant(type: Type, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number) {
if (!isUnitUnionType(type)) {
return type;
}
// We only narrow if all case expressions specify values with unit types
const switchTypes = getSwitchClauseTypes(switchStatement);
if (!switchTypes.length) {
return type;
@ -8223,7 +8221,7 @@ namespace ts {
if (!hasDefaultClause) {
return caseType;
}
const defaultType = filterType(type, t => !eachTypeContainedIn(t, switchTypes));
const defaultType = filterType(type, t => !(isUnitType(t) && contains(switchTypes, t)));
return caseType === neverType ? defaultType : getUnionType([caseType, defaultType]);
}