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[Sema] Downgrade multi-param default inference diag for methods #81887

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Merged
merged 1 commit into from
Jun 1, 2025
Merged

[Sema] Downgrade multi-param default inference diag for methods #81887

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11 changes: 9 additions & 2 deletions lib/Sema/TypeCheckConstraints.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -669,12 +669,19 @@ Type TypeChecker::typeCheckParameterDefault(Expr *&defaultValue,
affectedParams, [&](const unsigned index) { params << "#" << index; },
[&] { params << ", "; });

ctx.Diags.diagnose(
auto diag = ctx.Diags.diagnose(
defaultValue->getLoc(),
diag::
cannot_default_generic_parameter_inferrable_from_another_parameter,
paramInterfaceTy, params.str());
return Type();

// In Swift 6.2 and below we incorrectly missed checking this rule for
// methods, downgrade to a warning until the next language mode.
auto futureVersion = version::Version::getFutureMajorLanguageVersion();
if (!anchor->hasCurriedSelf() || ctx.isSwiftVersionAtLeast(futureVersion))
return Type();

diag.warnUntilFutureSwiftVersion();
}
}

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2 changes: 1 addition & 1 deletion test/Constraints/type_inference_from_default_exprs.swift
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Expand Up @@ -278,7 +278,7 @@ func testInferenceFromClosureVarInvalid<T>(x: T = { let x = "" as Int; return x
// https://github.com/swiftlang/swift/issues/72199
enum S72199_1 {
func testS72199_1<T>(_: T = 42, _: [T]) {}
// expected-error@-1 {{cannot use default expression for inference of 'T' because it is inferrable from parameters #0, #1}}
// expected-warning@-1 {{cannot use default expression for inference of 'T' because it is inferrable from parameters #0, #1; this will be an error in a future Swift language mode}}
}

func testS72199_2<T: P>(x: T.X, y: T = S()) { } // Ok
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11 changes: 11 additions & 0 deletions test/Constraints/type_inference_from_default_exprs_swift7.swift
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@@ -0,0 +1,11 @@
// RUN: %target-typecheck-verify-swift -swift-version 7
// REQUIRES: swift7

// https://github.com/swiftlang/swift/issues/72199
enum S72199_1 {
func testS72199_1<T>(_: T = 42, _: [T]) {}
// expected-error@-1 {{cannot use default expression for inference of 'T' because it is inferrable from parameters #0, #1}}
}

func testS72199<T>(_: T = 42, _: [T]) {}
// expected-error@-1 {{cannot use default expression for inference of 'T' because it is inferrable from parameters #0, #1}}