Relax signature collision rules for static extension methods #77603
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Specifically, two static extension methods are allowed to have the same signature (according to the current language rules) as long as all the following conditions are met: - methods have different return type and/or different return ref-ness - methods extending different types (ref-ness of the receiver parameter is not considered)
AlekseyTs
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Area-Compilers
Feature - Extension Everything
ghost
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the
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jcouv
reviewed
Mar 14, 2025
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| staticExtensionImplementationsWithoutReturn ??= new Dictionary<MethodSymbol, OneOrMany<MethodSymbol>>(MemberSignatureComparer.DuplicateSourceComparer); | ||
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| if (staticExtensionImplementationsWithoutReturn.TryGetValue(staticExtension, out OneOrMany<MethodSymbol> previousStaticExtension)) |
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@jjonescz, @dotnet/roslyn-compiler For the second review |
jcouv
reviewed
Mar 15, 2025
| // static public string M2(int x) => throw null; | ||
| Diagnostic(ErrorCode.ERR_MemberAlreadyExists, "M2").WithArguments("M2", "Extensions").WithLocation(12, 30) | ||
| ); | ||
| } |
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Do we expect this error?
[Fact]
public void TODO2()
{
var src = """
static class E
{
extension(object)
{
public void Method() { }
public static void Method() { }
}
}
""";
var comp = CreateCompilation(src);
comp.VerifyEmitDiagnostics(
// (6,28): error CS0111: Type 'E.extension(object)' already defines a member called 'Method' with the same parameter types
// public static void Method() { }
Diagnostic(ErrorCode.ERR_MemberAlreadyExists, "Method").WithArguments("Method", "E.extension(object)").WithLocation(6, 28));
}
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Do we expect this error?
Given the current rules, we do. This looks like M9 scenario in SignatureConflict_02. There is a PROTOTYPE comment regarding the current behavior
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The M9 scenario in SignatureConflict_02 is:
extension(int receiver)
{
public void M9() {}
}
extension(int receiver)
{
public static void M9(int x) {}
}
M9 generates conflicting signatures in metadata, so should generate an error.
But in the scenario above, the implementation methods have different signatures, so I would expect no error.
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so I would expect no error.
Are both methods static extensions?
jjonescz
approved these changes
Mar 17, 2025
AlekseyTs
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This was referenced Apr 1, 2025
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Specifically, two static extension methods are allowed to have the same signature (according to the current language rules) as long as all the following conditions are met:
Relates to test plan #76130