[][src]Module rustc_ast::tokenstream

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

Token Streams

TokenStreams represent syntactic objects before they are converted into ASTs. A TokenStream is, roughly speaking, a sequence (eg stream) of TokenTrees, which are themselves a single Token or a Delimited subsequence of tokens.


TokenStreams are persistent data structures constructed as ropes with reference counted-children. In general, this means that calling an operation on a TokenStream (such as slice) produces an entirely new TokenStream from the borrowed reference to the original. This essentially coerces TokenStreams into 'views' of their subparts, and a borrowed TokenStream is sufficient to build an owned TokenStream without taking ownership of the original.



A TokenStream is an abstract sequence of tokens, organized into TokenTrees.




When the main rust parser encounters a syntax-extension invocation, it parses the arguments to the invocation as a token-tree. This is a very loose structure, such that all sorts of different AST-fragments can be passed to syntax extensions using a uniform type.

Type Definitions