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Properly check relationships for intersections with union constraints

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This commit is contained in:
Anders Hejlsberg 2018-04-24 14:57:27 -07:00
parent 5d67f8ef68
commit ef8d5094b4
1 changed files with 35 additions and 0 deletions
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35
src/compiler/checker.ts
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@ -6428,6 +6428,26 @@ namespace ts {
return getConstraintOfDistributiveConditionalType(type) || getDefaultConstraintOfConditionalType(type);
}
function getUnionConstraintOfIntersection(type: IntersectionType) {
let constraints: Type[];
for (const t of type.types) {
if (t.flags & TypeFlags.Instantiable) {
const baseConstraint = getBaseConstraintOfType(t);
if (!(baseConstraint.flags & TypeFlags.Union)) {
return undefined;
}
constraints = append(constraints, baseConstraint);
}
}
if (constraints) {
const constraint = getIntersectionType(constraints);
if (constraint.flags & TypeFlags.Union) {
return constraint;
}
}
return undefined;
}
function getBaseConstraintOfInstantiableNonPrimitiveUnionOrIntersection(type: Type) {
if (type.flags & (TypeFlags.InstantiableNonPrimitive | TypeFlags.UnionOrIntersection)) {
const constraint = getResolvedBaseConstraint(<InstantiableType | UnionOrIntersectionType>type);
@ -10125,6 +10145,21 @@ namespace ts {
errorInfo = saveErrorInfo;
}
}
if (!result && source.flags & TypeFlags.Intersection && target.flags & TypeFlags.Union) {
// The combined constraint of an intersection type is the intersection of the constraints of
// the constituents. Since we break down union types before intersection types, if the target
// type is a union type and the source type is an intersection type with a combined constraint
// that is a union type, we need an extra check to see if the combined constraint is related to
// the target. For example, given two type variables T and U, each with the constraint
// 'string | number', the combined constraint of 'T & U' is 'string | number' and we need to
// check this constraint against the union on the target side.
const constraint = getUnionConstraintOfIntersection(<IntersectionType>source);
if (constraint) {
if (result = isRelatedTo(constraint, target, reportErrors)) {
errorInfo = saveErrorInfo;
}
}
}
}
isIntersectionConstituent = saveIsIntersectionConstituent;