syntax: Remove Nt(Impl,Trait,Foreign)Item

[petrochenkov]

Follow-up to #69366.
r? @Centril

[Centril]

Thanks. I wonder whether we have a test for trait items specifically that exercises the interaction with NtTraitItem and parameter names on Rust 2015. It doesn't seem like this would cause any problems re. that as Annotatable::TraitItems would still cause us to parse using parse_trait_item. But could you double check? r=me with that and these comments considered.

[petrochenkov]

I wonder whether we have a test for trait items specifically that exercises the interaction with NtTraitItem and parameter names on Rust 2015.

These nonterminals shouldn't be observable during parsing, they are an implementation details of, well, not even expansion, but pretty-printing.
If tokens in a TokenStream are packed into a nonterminal with an AST piece inside, then they are printed more nicely using the AST pretty-printer.

After #62667 tokens streams themselves are printed pretty nicely, so I want to try removing this piece of code in expand.rs entirely in a follow-up PR.

[petrochenkov]

Updated.

[petrochenkov]

@bors r=Centril

[bors]

📌 Commit d134385 has been approved by Centril