Referencing assembly with improper use of TypeSpec compiles but does not run

[nguerrera]

There is an issue in the ECMA-335 CLI specification where it is implied that (CLASS | VALUETYPE) can be followed by a TypeSpec token, when in fact only TypeRef and TypeDef are valid. When referencing a bad assembly that has such a signature, Roslyn recurses into the TypeSpec. It then emits the signature in the proper way, with the TypeSpec contents embedded into the MemberRef signature, but the call cannot bind to the bad method at runtime.

I have started to document such spec issues in dotnet/corefx#5435 and I'm now filing the bugs I found while experimenting to write that up.

Native csc.exe produced an error at compilation time.

Repro steps

• git clone https://github.com/nguerrera/signature-repros
• cd signature-repros
• build.bat
• csc.exe UseTypeSpecInWrongPlace.cs /r:TypeSpecInWrongPlace.exe
• UseTypeSpecInWrongPlace.exe

Expected result

Compilation fails with suitable error message.

Actual result

Roslyn

• compilation succeeds without warnings
• run fails

System.MissingMethodException: Method not found:  
    'Void User.X(System.Collections.Generic.List`1<Int32>)'.

Native csc

• compilation fails as expected:

UseTypeSpecInWrongPlace.cs(19,9): error CS0570: 'X' is not supported by the language

cc @tmat @gafter @AlekseyTs

[gafter]

/cc @jaredpar