I'm listing a number of scenarios that are broken in similar ways. Hopefully they can be fixed with a single stone. If not, feel free to split this issue as necessary.

• ExplicitType var x = (nint)0; produces IntPtr instead of nint.
• Same for IntroduceLocal, GenerateImplementation (implementing an interface), GenerateOverride (typing override and using completion).
• Same ExtractMethod, ExtractLocalFunction, AddParameter. Those also generate IntPtr parameters.
• Haven't tested MetadataAsSource, but it is likely the same.

Relates to #38821