eff35e59c6
The primary purpose of this commit is to introduce the dyn_star flag so we can begin experimenting with implementation. In order to have something to do in the feature gate test, we also add parser support for `dyn* Trait` objects. These are currently treated just like `dyn Trait` objects, but this will change in the future. Note that for now `dyn* Trait` is experimental syntax to enable implementing some of the machinery needed for async fn in dyn traits without fully supporting the feature.
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: