Collection expressions: prefer ReadOnlySpan<T> over Span<T> in overload resolution #70328
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src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
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src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
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…ion/OverloadResolution.cs
src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs
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…ion/OverloadResolution.cs
| static void F1(int[] value) { } | ||
| static void F1(object[] value) { } |
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I don't remember the exact notes but isn't this supposed to be unambiguous just like (int,int,int) and (object,object,object)?
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I'm not aware of a decision to prefer one array type over another for a collection expression conversion in overload resolution, other than the existing rule to prefer type T1 over T2 if there is an implicit conversion from T1 to T2.
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My mistake, I thought most-specific rules can interact with the common-type from elements.
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Relevant notes: https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-09-20.md
Though that's only a special-case around ref structs to resolve this, and only in one direction.
| Diagnostic(ErrorCode.ERR_AmbigCall, "F1").WithArguments("Program.F1(System.ReadOnlySpan<int>)", "Program.F1(System.ReadOnlySpan<object>)").WithLocation(10, 9), | ||
| // (11,9): error CS0121: The call is ambiguous between the following methods or properties: 'Program.F2(Span<string>)' and 'Program.F2(Span<object>)' | ||
| // F2(["a", "b"]); | ||
| Diagnostic(ErrorCode.ERR_AmbigCall, "F2").WithArguments("Program.F2(System.Span<string>)", "Program.F2(System.Span<object>)").WithLocation(11, 9)); |
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This doesn't feel right to me, but I can see that it adheres to the specification. I think we should resolve at the same time as #70238, hopefully in 17.9.
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Collection expressions: prefer ReadOnlySpan<T> over Span<T> in overload resolution (#70328)
See updated better conversion from expression: dotnet/csharplang#7591
Fixes #70318