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[CSSimplify] Don't propagate contextual parameter type if it's a pack… #64531

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Merged
merged 1 commit into from
Mar 23, 2023
Merged

[CSSimplify] Don't propagate contextual parameter type if it's a pack… #64531

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5 changes: 5 additions & 0 deletions lib/Sema/CSSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11020,6 +11020,11 @@ bool ConstraintSystem::resolveClosure(TypeVariableType *typeVar,
if (contextualTy->isTypeVariableOrMember())
return false;

// Cannot propagate pack expansion type from context,
// it has to be handled by type matching logic.
if (contextualTy->is<PackExpansionType>())
return false;
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If I understand everything correctly we could allow that by using getPatternType but I think in vast majority of cases (if not all) it would result in a type variable anyway which is not a suitable type too.

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We would need to wait until the pattern type is fully substituted and flattened. The pattern type in this case will be substituted with PackType{String}, and the pack expansion will flatten the pack type into just String

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Right, I figured that it better to let it go through the matching logic than try to do anything fancy here.


// If contextual type has an error, let's wait for inference,
// otherwise contextual would interfere with diagnostics.
if (contextualTy->hasError())
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10 changes: 10 additions & 0 deletions test/Constraints/pack-expansion-expressions.swift
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Expand Up @@ -261,3 +261,13 @@ func invalidRepeat<each T>(t: repeat each T) {
_ = [repeat each t]
// expected-error@-1 {{value pack expansion can only appear inside a function argument list or tuple element}}
}

func test_pack_expansions_with_closures() {
func takesVariadicFunction<each T>(function: (repeat each T) -> Int) {}

func test(fn: (Int, String) -> Int, x: Int) {
takesVariadicFunction { fn(x, "") } // Ok
takesVariadicFunction { y in fn(x, y) } // Ok
takesVariadicFunction { y, z in fn(y, z) } // Ok
}
}