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Only get apparent type when constraint includes nullable types

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This commit is contained in:
Anders Hejlsberg
2017-05-04 10:20:04 -07:00
parent 238067eb3b
commit 4123068f19
1 changed files with 6 additions and 5 deletions
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11
src/compiler/checker.ts
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@@ -11717,17 +11717,18 @@ namespace ts {
parent.kind === SyntaxKind.ElementAccessExpression && (<ElementAccessExpression>parent).expression === node;
}
function typeHasNullableConstraint(type: Type) {
return type.flags & TypeFlags.TypeVariable && maybeTypeOfKind(getBaseConstraintOfType(type) || emptyObjectType, TypeFlags.Nullable);
}
function getDeclaredOrApparentType(symbol: Symbol, node: Node) {
// When a node is the left hand expression of a property access, element access, or call expression,
// and the type of the node includes type variables with constraints that are nullable, we fetch the
// apparent type of the node *before* performing control flow analysis such that narrowings apply to
// the constraint type.
const type = getTypeOfSymbol(symbol);
if (isApparentTypePosition(node) && maybeTypeOfKind(type, TypeFlags.TypeVariable)) {
const apparentType = mapType(getWidenedType(type), getApparentType);
if (maybeTypeOfKind(apparentType, TypeFlags.Nullable)) {
return apparentType;
}
if (isApparentTypePosition(node) && forEachType(type, typeHasNullableConstraint)) {
return mapType(getWidenedType(type), getApparentType);
}
return type;
}