Can't decompile to switch-expression when value is implicitly cast

[Pathoschild]

ILSpy can't decompile a switch statement when the source value is implicitly cast. This broke in ILSpy 6.2+.

Steps to reproduce

1. Unzip the repro DLL, which contains this code:

   public class SampleClass
   {
       public string SampleMethod()
       {
           string value = new ImplicitlyCastToString();
           return value switch
           {
               "foo" => "foo",
               "bar" => "bar",
               "quux" => "quux",
               _ => "default"
           };
       }
   }
   
   public class ImplicitlyCastToString
   {
       public static implicit operator string(ImplicitlyCastToString val)
       {
           return "foo";
       }
   }

2. Decompile the .dll file with ILSpy.

Resulting code:

ILSpy 6.1 (working)	ILSpy 6.2+ (broken)
return (string)new ImplicitlyCastToString() switch { "foo" => "foo", "bar" => "bar", "quux" => "quux", _ => "default", };	return new ImplicitlyCastToString() switch { 0L => "foo", 1L => "bar", 2L => "quux", _ => "default", };

Details

• Product in use: ILSpy
• Version in use:

  tested version	result
  6.1.0.5902	✓ ok
  6.2.0.6062-preview1	✓ ok
  6.2.0.6118-preview2	✘ fails
  6.2.0.6124	✘ fails
  6.2.1.6137	✘ fails
  7.0.0.6225-preview1	✘ fails

[CreateAndInject]

@Pathoschild I'm sorry, I just want to know how to use markdown to generate this table with multi content:

This code can't work:

[Pathoschild]

@CreateAndInject GitHub allows some basic HTML for cases like this; here's the code for that table.

[CreateAndInject]

@Pathoschild Thanks, I have collapsed my content.

[siegfriedpammer]

See https://sharplab.io/#v2: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

To me this looks like a bug in the compiler because there is an inconsistency between switch-expressions and switch-statements. The error produced by the C# compiler is error CS0029: Cannot implicitly convert type 'string' to 'ImplicitlyCastToString', which is strange, because there exists a user-defined implicit conversion from ImplicitlyCastToString to string. Should we report this to the Roslyn repository?