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Merge pull request #22989 from Microsoft/fixImpliedConstraint

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Fix implied constraints in conditional types
This commit is contained in:
Anders Hejlsberg
2018-03-29 17:06:16 -07:00
committed by GitHub
parent b47c1fd5a1 f1bb530a3a
commit 7714a2bb5b
6 changed files with 180 additions and 6 deletions
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12
src/compiler/checker.ts
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@@ -7407,7 +7407,7 @@ namespace ts {
function getConstrainedTypeVariable(typeVariable: TypeVariable, node: Node) {
let constraints: Type[];
while (isPartOfTypeNode(node)) {
while (node && !isStatement(node)) {
const parent = node.parent;
if (parent.kind === SyntaxKind.ConditionalType && node === (<ConditionalTypeNode>parent).trueType) {
const constraint = getImpliedConstraint(typeVariable, (<ConditionalTypeNode>parent).checkType, (<ConditionalTypeNode>parent).extendsType);
@@ -8356,17 +8356,17 @@ namespace ts {
// resolution of the conditional type such that a later instantiation will properly distribute
// over union types.
const isDeferred = root.isDistributive && maybeTypeOfKind(checkType, TypeFlags.Instantiable);
let combinedMapper: TypeMapper;
if (root.inferTypeParameters) {
const context = createInferenceContext(root.inferTypeParameters, /*signature*/ undefined, InferenceFlags.None);
let combinedMapper: TypeMapper;
if (root.inferTypeParameters) {
const context = createInferenceContext(root.inferTypeParameters, /*signature*/ undefined, InferenceFlags.None);
if (!isDeferred) {
// We don't want inferences from constraints as they may cause us to eagerly resolve the
// conditional type instead of deferring resolution. Also, we always want strict function
// types rules (i.e. proper contravariance) for inferences.
inferTypes(context.inferences, checkType, extendsType, InferencePriority.NoConstraints | InferencePriority.AlwaysStrict);
}
combinedMapper = combineTypeMappers(mapper, context);
}
combinedMapper = combineTypeMappers(mapper, context);
}
if (!isDeferred) {
// Return union of trueType and falseType for 'any' since it matches anything
if (checkType.flags & TypeFlags.Any) {