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Improve type inference for types with same generic type alias

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This commit is contained in:
Anders Hejlsberg
2016-11-11 07:39:51 -08:00
parent 1c7ec6b8ce
commit 364142c062
1 changed files with 10 additions and 0 deletions
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src/compiler/checker.ts
+10
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@@ -8318,6 +8318,16 @@ namespace ts {
if (!couldContainTypeParameters(target)) {
return;
}
if (source.aliasSymbol && source.aliasTypeArguments && source.aliasSymbol === target.aliasSymbol) {
// Source and target are types originating in the same generic type alias declaration.
// Simply infer from source type arguments to target type arguments.
const sourceTypes = source.aliasTypeArguments;
const targetTypes = target.aliasTypeArguments;
for (let i = 0; i < sourceTypes.length; i++) {
inferFromTypes(sourceTypes[i], targetTypes[i]);
}
return;
}
if (source.flags & TypeFlags.Union && target.flags & TypeFlags.Union && !(source.flags & TypeFlags.Enum && target.flags & TypeFlags.Enum) ||
source.flags & TypeFlags.Intersection && target.flags & TypeFlags.Intersection) {
// Source and target are both unions or both intersections. If source and target