Use .interfaceimpl type syntax

[ltrzesniewski]

Problem

I noticed the following output when decompiling an assembly:

That implements .custom part seemed wrong, and indeed, ildasm uses another syntax instead: .interfaceimpl type (see here).

Here is the result:

Solution

• Any comments on the approach taken, its consistency with surrounding code, etc.

  This PR moves the custom attributes on interface implementations inside the type body and adds one .interfaceimpl type declaration for each interface implementation which has a custom attribute.

• Which part of this PR is most in need of attention/improvement?

  While implementing this, I noticed that ilasm is inconsistent with ildasm when multiple attributes are applied to an interface implementation. I believe ilasm is wrong here, and reported the following issue:
  ilasm does not apply multiple custom attributes on interface implementations dotnet/runtime#82373

  Because of this, the unit test only applies a single attribute on the interface implementation. I didn't want to add an additional .expected.il file just because of this inconsistency.

  This PR implements the same behavior as in ildasm.

  As for the UI, I wasn't sure if I should highlight the type keyword in green (which looked wrong) or in blue (which could lead to many false positives), so I left it as-is.

• At least one test covering the code changed

[ltrzesniewski]

BTW this is how dotPeek displays an interface implementation with two custom attributes:

Note the indentation, which clarifies the intent.

[siegfriedpammer]

• As for the UI, I wasn't sure if I should highlight the type keyword in green (which looked wrong) or in blue (which could lead to many false positives), so I left it as-is.

As ilasm treats type as a keyword and fails to assemble a method that is named type: error : syntax error at token 'type'. I would say that you can safely highlight it, there would be no confusion in existing code.

[ltrzesniewski]

Right, I should have tested it. I added the type keyword.

But upon checking, I noticed that single-quoted identifiers are still highlighted as kewords. This also applies to other keywords such as instance:

So I also fixed that in this PR: