Generic type argument inference fails in the face of implicit cast (e.g. Span<T> to ReadOnlySpan<T>)

[nietras]

Version Used: Compiler version: '4.5.0-2.22580.13 (ea0b6351)'. Language version: 11.0.

Even a simple program like below using Span<T> will fail in the face of implicit cast. This means we basically have to have both Span<T> and ReadOnlySpan<T> overloads for all methods relevant for this which is a huge hassle. This of course extends to other cases not just Span<> but it has become quite pervasive with the introduction of spans and read only spans, since implicit casts are everywhere now.

Span<int> ints = stackalloc int[2];

// Error CS0411 The type arguments for method 'Method<T>(ReadOnlySpan<T>)'
// cannot be inferred from the usage. Try specifying the type arguments
// explicitly.
Method(ints);

static void Method<T>(ReadOnlySpan<T> span) { }

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

</Project>

Diagnostic Id: CS0411

Expected Behavior: Infer the type! 🙏 Especially when the implicit type conversion is clear (e.g. there is just one or something).

Actual Behavior: Compile error.

PS: This probably has been reported before, but I could not find any existing issue probably due to lack of search skills. Or it might have to be reported on csharplang, I don't know. 😅

[CyrusNajmabadi]

This looks to be a language request.