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forked from verus-lang/verus
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129/// Parse the input TokenStream of a macro, triggering a compile error if the/// tokens fail to parse.////// Refer to the [`parse` module] documentation for more details about parsing/// in Syn.////// [`parse` module]: mod@crate::parse////// <br>////// # Intended usage////// This macro must be called from a function that returns/// `proc_macro::TokenStream`. Usually this will be your proc macro entry point,/// the function that has the #\[proc_macro\] / #\[proc_macro_derive\] //// #\[proc_macro_attribute\] attribute.////// ```/// # extern crate proc_macro;/// #/// use proc_macro::TokenStream;/// use syn::{parse_macro_input, Result};/// use syn::parse::{Parse, ParseStream};////// struct MyMacroInput {/// /* ... *//// }////// impl Parse for MyMacroInput {/// fn parse(input: ParseStream) -> Result<Self> {/// /* ... *//// # Ok(MyMacroInput {})/// }/// }////// # const IGNORE: &str = stringify! {/// #[proc_macro]/// # };/// pub fn my_macro(tokens: TokenStream) -> TokenStream {/// let input = parse_macro_input!(tokens as MyMacroInput);////// /* ... *//// # TokenStream::new()/// }/// ```////// <br>////// # Usage with Parser////// This macro can also be used with the [`Parser` trait] for types that have/// multiple ways that they can be parsed.////// [`Parser` trait]: crate::parse::Parser////// ```/// # extern crate proc_macro;/// #/// # use proc_macro::TokenStream;/// # use syn::{parse_macro_input, Result};/// # use syn::parse::ParseStream;/// #/// # struct MyMacroInput {}/// #/// impl MyMacroInput {/// fn parse_alternate(input: ParseStream) -> Result<Self> {/// /* ... *//// # Ok(MyMacroInput {})/// }/// }////// # const IGNORE: &str = stringify! {/// #[proc_macro]/// # };/// pub fn my_macro(tokens: TokenStream) -> TokenStream {/// let input = parse_macro_input!(tokens with MyMacroInput::parse_alternate);////// /* ... *//// # TokenStream::new()/// }/// ```////// <br>////// # Expansion////// `parse_macro_input!($variable as $Type)` expands to something like:////// ```no_run/// # extern crate proc_macro;/// #/// # macro_rules! doc_test {/// # ($variable:ident as $Type:ty) => {/// match syn::parse::<$Type>($variable) {/// Ok(syntax_tree) => syntax_tree,/// Err(err) => return proc_macro::TokenStream::from(err.to_compile_error()),/// }/// # };/// # }/// #/// # fn test(input: proc_macro::TokenStream) -> proc_macro::TokenStream {/// # let _ = doc_test!(input as syn::Ident);/// # proc_macro::TokenStream::new()/// # }/// ```#[macro_export]#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))]macro_rules! parse_macro_input { ($tokenstream:ident as $ty:ty) => { match $crate::parse::<$ty>($tokenstream) { $crate::__private::Ok(data) => data, $crate::__private::Err(err) => { return $crate::__private::TokenStream::from(err.to_compile_error()); } } }; ($tokenstream:ident with $parser:path) => { match $crate::parse::Parser::parse($parser, $tokenstream) { $crate::__private::Ok(data) => data, $crate::__private::Err(err) => { return $crate::__private::TokenStream::from(err.to_compile_error()); } } }; ($tokenstream:ident) => { $crate::parse_macro_input!($tokenstream as _) };}