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Implement `gen` blocks in the 2024 edition Coroutines tracking issue https://github.com/rust-lang/rust/issues/43122 `gen` block tracking issue https://github.com/rust-lang/rust/issues/117078 This PR implements `gen` blocks that implement `Iterator`. Most of the logic with `async` blocks is shared, and thus I renamed various types that were referring to `async` specifically. An example usage of `gen` blocks is ```rust fn foo() -> impl Iterator<Item = i32> { gen { yield 42; for i in 5..18 { if i.is_even() { continue } yield i * 2; } } } ``` The limitations (to be resolved) of the implementation are listed in the tracking issue
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: