364b908d57
It's only needed for macro expansion, not as a general element in the AST. This commit removes it, adds `NtOrTt` for the parser and macro expansion cases, and renames the variants in `NamedMatch` to better match the new type.
The rustc_ast crate contains those things concerned purely with syntax
– that is, the AST ("abstract syntax tree"), along with some definitions for tokens and token streams, data structures/traits for mutating ASTs, and shared definitions for other AST-related parts of the compiler (like the lexer and macro-expansion).
For more information about how these things work in rustc, see the rustc dev guide: