Only Left and returnValue gets checked for dynamic in signature

[gero3]

In CSharpcompilation there was a signature check for dynamic Types but only left and return were checked. I was running my roslyn analyser to check for identical subexpressions over this repository to get some edgecases that I forgot about. This came out as response

[gero3]

This should resolve #69215.

[CyrusNajmabadi]

definitely looks like a good bug you've caught. :)

would need a test to go along with this. Thsi also might be a breaking change in some way. Compiler will have to look into that and see if this needs to be doc'ed.

[gero3]

I don't think it will functionally change something because I can't seem to figure out how to have the right dynamic type without a return type that is also dynamic.

[gero3]

As well as I understand the function of the code, the function validateSignature should reject all invalid signatures for creating
a SynthesizedIntrinsicOperatorSymbol. So It should throw when the type of result is nondynamic while either left or right is dynamic. This is based on the debug assert in the constructor of SynthesizedIntrinsicOperatorSymbol found on Line 41.

I don't know if this needs extra checks due to only being Debug.Assert.

Otherwise I would change the code to the following:

               if (csharpReturnType.TypeKind is TypeKind.Dynamic && csharpLeftType.TypeKind is TypeKind.Dynamic ||
                   csharpReturnType.TypeKind is TypeKind.Dynamic && csharpRightType.TypeKind is TypeKind.Dynamic)
               {
                   return;
               }

I could also add tests to check if it throws when the returntype is non dynamic while left and/or right are dynamic.

[AlekseyTs]

LGTM (commit 1)

[AlekseyTs]

@dotnet/roslyn-compiler For the second review

[jcouv]

LGTM Thanks (iteration 1)

[jcouv]

Thanks for the contribution @gero3 !

[gero3]

No problem