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Merge pull request #25287 from Microsoft/skipToNonNullTargets

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Skip to non null targets in error messages
This commit is contained in:
Daniel Rosenwasser
2018-06-28 22:26:36 -07:00
committed by GitHub
parent 2a19580144 584e923f42
commit f23c180a38
7 changed files with 119 additions and 11 deletions
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19
src/compiler/checker.ts
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@@ -10631,6 +10631,23 @@ namespace ts {
target = getSimplifiedType(target);
}
// Try to see if we're relating something like `Foo` -> `Bar | null | undefined`.
// If so, reporting the `null` and `undefined` in the type is hardly useful.
// First, see if we're even relating an object type to a union.
// Then see if the target is stripped down to a single non-union type.
// Note
// * We actually want to remove null and undefined naively here (rather than using getNonNullableType),
// since we don't want to end up with a worse error like "`Foo` is not assignable to `NonNullable<T>`"
// when dealing with generics.
// * We also don't deal with primitive source types, since we already halt elaboration below.
if (target.flags & TypeFlags.Union && source.flags & TypeFlags.Object &&
(target as UnionType).types.length <= 3 && maybeTypeOfKind(target, TypeFlags.Nullable)) {
const nullStrippedTarget = extractTypesOfKind(target, ~TypeFlags.Nullable);
if (!(nullStrippedTarget.flags & (TypeFlags.Union | TypeFlags.Never))) {
target = nullStrippedTarget;
}
}
// both types are the same - covers 'they are the same primitive type or both are Any' or the same type parameter cases
if (source === target) return Ternary.True;
@@ -12223,7 +12240,7 @@ namespace ts {
if (deferredGlobalNonNullableTypeAlias !== unknownSymbol) {
return getTypeAliasInstantiation(deferredGlobalNonNullableTypeAlias, [type]);
}
return getTypeWithFacts(type, TypeFacts.NEUndefinedOrNull); // Type alias unavailable, fall back to non-higherorder behavior
return getTypeWithFacts(type, TypeFacts.NEUndefinedOrNull); // Type alias unavailable, fall back to non-higher-order behavior
}
function getNonNullableType(type: Type): Type {