method / constant was impl on primitive type

Compilation Successful when method / constant was impl on primitive type E0390

• Fixing this issue, will also help gccrs to emit error codes similiar to rustc.
• You can view the same on compiler-explorer

I tried this code from E0390:

#![allow(unused)]
fn main() {
struct Foo {
    x: i32
}

impl *mut Foo {}
// error: cannot define inherent `impl` for primitive types
}

I expected to see this happen:

• Give error like rustc, i.e.,

error[E0390]: only a single inherent implementation marked with `#[lang = "mut_ptr"]` is allowed for the `*mut T` primitive

Instead, this happened:

• Compiled Successfully.

Compiler returned: 0

Meta

• What version of Rust GCC were you using, git sha dba8bc5bf8247161b6eff4f738b6479382f770f2.
• gccrs (Compiler-Explorer-Build-gcc-22f4c74767bddcb9813dca06fc6a354a67d05343-binutils-2.40) 13.0.1 20230417 (experimental)

Start by reproducing the impl *mut Foo {} example from Rust error E0390, using the linked Compiler Explorer case and the stated gccrs version. Compare gccrs's successful compilation with rustc's diagnostic; done means gccrs rejects the primitive-type implementation with the expected E0390-style error.