Fixed local extends constraints of infer type parameters when they can contain type variables
#60345
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…can contain type variables
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Andarist
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Oct 26, 2024
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| function maybeCloneInferTypeParameter(p: TypeParameter) { | ||
| return getConstraintDeclaration(p) && couldContainTypeVariables(getConstraintFromTypeParameter(p)!) ? cloneTypeParameter(p) : p; | ||
| } |
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this only clones type parameters with "local" constraints (the ones added by infer R extends C syntax)
It could do the same with all constraints, using this patch:
git diff
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a8803f5823..52f44bcebe 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -19117,9 +19117,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
}
const context = createInferenceContext(freshParams, /*signature*/ undefined, InferenceFlags.None);
- if (mapper) {
- context.nonFixingMapper = combineTypeMappers(context.nonFixingMapper, mapper);
- }
if (!checkTypeDeferred) {
// 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
@@ -19220,7 +19217,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
}
function maybeCloneInferTypeParameter(p: TypeParameter) {
- return getConstraintDeclaration(p) && couldContainTypeVariables(getConstraintFromTypeParameter(p)!) ? cloneTypeParameter(p) : p;
+ const constraint = getConstraintFromTypeParameter(p);
+ return constraint && couldContainTypeVariables(constraint) ? cloneTypeParameter(p) : p;
}
function getTrueTypeFromConditionalType(type: ConditionalType) {
diff --git a/tests/baselines/reference/inferTypes1.types b/tests/baselines/reference/inferTypes1.types
index edc97a2ea1..f6018d54a3 100644
--- a/tests/baselines/reference/inferTypes1.types
+++ b/tests/baselines/reference/inferTypes1.types
@@ -1,5 +1,8 @@
//// [tests/cases/conformance/types/conditional/inferTypes1.ts] ////
+=== Performance Stats ===
+Instantiation count: 1,000
+
=== inferTypes1.ts ===
type Unpacked<T> =
>Unpacked : Unpacked<T>As we can see, we could drop the context.nonFixingMapper manipulation and simplify the logic here - but that would create more type parameter clones and that's even caught by this diff (Instantiation count was reported by one of the tests when using this patch)
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thank you very much @Andarist, how long do you reckon before this might be merged ? |
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@zedryas that's not up to me, we have to wait for the review and merge by one of the TS team members |
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@typescript-bot test it |
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@jakebailey Here are the results of running the user tests with tsc comparing Everything looks good! |
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Hey @jakebailey, the results of running the DT tests are ready. Everything looks the same! |
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@jakebailey Here they are:
tscComparison Report - baseline..pr
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@jakebailey Here are the results of running the top 400 repos with tsc comparing Everything looks good! |
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Any update on this merge request? cc @weswigham (i do tag because you were the reviewer on #57362 ) |
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fixes #60299
this reverts a good chunk of #57362 but it also makes some modifications to the code that was removed there
cc @weswigham