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Defer conditional types with parenthesized multi-element tuple types in extends clause (#56271)

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Co-authored-by: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
This commit is contained in:
Mateusz Burzyński
2023-12-08 21:21:04 +01:00
committed by GitHub
parent b436976bd3
commit 41ec497211
4 changed files with 223 additions and 3 deletions
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9
src/compiler/checker.ts
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@@ -967,6 +967,7 @@ import {
skipParentheses,
skipTrivia,
skipTypeChecking,
skipTypeParentheses,
some,
SourceFile,
SpreadAssignment,
@@ -18490,7 +18491,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return constraint && (isGenericObjectType(constraint) || isGenericIndexType(constraint)) ? cloneTypeParameter(p) : p;
}
function isSimpleTupleType(node: TypeNode) {
function isSimpleTupleType(node: TypeNode): boolean {
return isTupleTypeNode(node) && length(node.elements) > 0 &&
!some(node.elements, e => isOptionalTypeNode(e) || isRestTypeNode(e) || isNamedTupleMember(e) && !!(e.questionToken || e.dotDotDotToken));
}
@@ -18521,11 +18522,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
if (checkType === wildcardType || extendsType === wildcardType) {
return wildcardType;
}
const checkTypeNode = skipTypeParentheses(root.node.checkType);
const extendsTypeNode = skipTypeParentheses(root.node.extendsType);
// When the check and extends types are simple tuple types of the same arity, we defer resolution of the
// conditional type when any tuple elements are generic. This is such that non-distributable conditional
// types can be written `[X] extends [Y] ? ...` and be deferred similarly to `X extends Y ? ...`.
const checkTuples = isSimpleTupleType(root.node.checkType) && isSimpleTupleType(root.node.extendsType) &&
length((root.node.checkType as TupleTypeNode).elements) === length((root.node.extendsType as TupleTypeNode).elements);
const checkTuples = isSimpleTupleType(checkTypeNode) && isSimpleTupleType(extendsTypeNode) &&
length((checkTypeNode as TupleTypeNode).elements) === length((extendsTypeNode as TupleTypeNode).elements);
const checkTypeDeferred = isDeferredType(checkType, checkTuples);
let combinedMapper: TypeMapper | undefined;
if (root.inferTypeParameters) {