Library for parsing function signature without parsing function body #16
Description
The Syn crate has fairly coarse compile-time control over the set of available syntax tree types. There is default-features = false mode where only the parsing API is provided with no syntax tree types at all, there is features = ["derive"] which is the default and supports structs and enums, and there is features = ["full"] which supports all possible Rust syntax.
Sometimes Rust macros, especially attribute macros, need to parse just slightly more than what is exposed by the default feature set. For example wasm-bindgen wants to parse function signatures but not their bodies. That means there should be no need for any of the expression-parsing logic enabled by features = ["full"]. They could save compile time by using features = ["derive"] in combination with a library that just parses function signatures.
pub struct Function {
/* ... */
}
pub fn parse_signature_only(function: TokenStream) -> syn::Result<Function>;The return struct would look like pretty much like syn::ItemFn except where the function body is kept as an unparsed TokenStream instead of a fully parsed syn::Block.