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Allow non-unit types in union discriminants #27695

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Merged
ahejlsberg merged 5 commits into from
Oct 15, 2018
Merged

Allow non-unit types in union discriminants #27695

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d069875
Allow discriminant property to contain some non-unit types
ahejlsberg Oct 10, 2018
c110f57
Discriminant must include at least one unit type and no instantiable …
ahejlsberg Oct 10, 2018
7737cd5
Accept new baselines
ahejlsberg Oct 10, 2018
22907bf
Add tests
ahejlsberg Oct 10, 2018
6cdba6d
Accept new baselines
ahejlsberg Oct 10, 2018
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Allow discriminant property to contain some non-unit types
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@ahejlsberg
ahejlsberg committed Oct 10, 2018
commit d0698751ce06814d740b22511c363d2a88a4a1bc
6 changes: 5 additions & 1 deletion src/compiler/checker.ts
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Expand Up @@ -12919,6 +12919,10 @@ 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 :
Expand Down Expand Up @@ -14217,7 +14221,7 @@ namespace ts {
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) && maybeUnitType(getTypeOfSymbol(prop));
}
return !!(<TransientSymbol>prop).isDiscriminantProperty;
}
Expand Down