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When inferring from XXX to T | XXX make no inferece for T (instead of never)

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Anders Hejlsberg 2019-07-23 06:38:49 -07:00
parent b822def6ef
commit 3206f5fb94
1 changed files with 7 additions and 5 deletions
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12
src/compiler/checker.ts
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@ -15515,16 +15515,18 @@ namespace ts {
// removing the identically matched constituents. For example, when inferring from // removing the identically matched constituents. For example, when inferring from
// 'string | string[]' to 'string | T' we reduce the types to 'string[]' and 'T'. // 'string | string[]' to 'string | T' we reduce the types to 'string[]' and 'T'.
if (matchingTypes) { if (matchingTypes) {
source = removeTypesFromUnionOrIntersection(<UnionOrIntersectionType>source, matchingTypes); const s = removeTypesFromUnionOrIntersection(<UnionOrIntersectionType>source, matchingTypes);
target = removeTypesFromUnionOrIntersection(<UnionOrIntersectionType>target, matchingTypes); const t = removeTypesFromUnionOrIntersection(<UnionOrIntersectionType>target, matchingTypes);
if (!(s && t)) return;
source = s;
target = t;
} }
} }
else if (target.flags & TypeFlags.Union && !(target.flags & TypeFlags.EnumLiteral) || target.flags & TypeFlags.Intersection) { else if (target.flags & TypeFlags.Union && !(target.flags & TypeFlags.EnumLiteral) || target.flags & TypeFlags.Intersection) {
const matched = findMatchedType(source, <UnionOrIntersectionType>target); const matched = findMatchedType(source, <UnionOrIntersectionType>target);
if (matched) { if (matched) {
inferFromTypes(matched, matched); inferFromTypes(matched, matched);
source = target.flags & TypeFlags.Union ? neverType : unknownType; return;
target = removeTypesFromUnionOrIntersection(<UnionOrIntersectionType>target, [matched]);
} }
} }
else if (target.flags & (TypeFlags.IndexedAccess | TypeFlags.Substitution)) { else if (target.flags & (TypeFlags.IndexedAccess | TypeFlags.Substitution)) {
@ -15993,7 +15995,7 @@ namespace ts {
reducedTypes.push(t); reducedTypes.push(t);
} }
} }
return type.flags & TypeFlags.Union ? getUnionType(reducedTypes) : getIntersectionType(reducedTypes); return reducedTypes.length ? type.flags & TypeFlags.Union ? getUnionType(reducedTypes) : getIntersectionType(reducedTypes) : undefined;
} }
function hasPrimitiveConstraint(type: TypeParameter): boolean { function hasPrimitiveConstraint(type: TypeParameter): boolean {