e094ee5f10
Using an obviously-placeholder syntax. An RFC would still be needed before this could have any chance at stabilization, and it might be removed at any point. But I'd really like to have it in nightly at least to ensure it works well with try_trait_v2, especially as we refactor the traits.
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: