diff options
Diffstat (limited to 'third_party/rust/syn/src/parse_macro_input.rs')
| -rw-r--r-- | third_party/rust/syn/src/parse_macro_input.rs | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/third_party/rust/syn/src/parse_macro_input.rs b/third_party/rust/syn/src/parse_macro_input.rs new file mode 100644 index 0000000000..6163cd70af --- /dev/null +++ b/third_party/rust/syn/src/parse_macro_input.rs @@ -0,0 +1,179 @@ +/// 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); +/// +/// /* ... */ +/// # "".parse().unwrap() +/// } +/// ``` +/// +/// <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); +/// +/// /* ... */ +/// # "".parse().unwrap() +/// } +/// ``` +/// +/// <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>($variable) { +/// Ok(syntax_tree) => syntax_tree, +/// Err(err) => return proc_macro::TokenStream::from(err.to_compile_error()), +/// } +/// # }; +/// # } +/// # +/// # fn test(input: proc_macro::TokenStream) -> proc_macro::TokenStream { +/// # let _ = doc_test!(input as syn::Ident); +/// # proc_macro::TokenStream::new() +/// # } +/// ``` +#[macro_export] +#[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))] +macro_rules! parse_macro_input { + ($tokenstream:ident as $ty:ty) => { + match $crate::parse_macro_input::parse::<$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 _) + }; +} + +//////////////////////////////////////////////////////////////////////////////// +// Can parse any type that implements Parse. + +use crate::parse::{Parse, ParseStream, Parser, Result}; +use proc_macro::TokenStream; + +// Not public API. +#[doc(hidden)] +pub fn parse<T: ParseMacroInput>(token_stream: TokenStream) -> Result<T> { + T::parse.parse(token_stream) +} + +// Not public API. +#[doc(hidden)] +pub trait ParseMacroInput: Sized { + fn parse(input: ParseStream) -> Result<Self>; +} + +impl<T: Parse> ParseMacroInput for T { + fn parse(input: ParseStream) -> Result<Self> { + <T as Parse>::parse(input) + } +} + +//////////////////////////////////////////////////////////////////////////////// +// Any other types that we want `parse_macro_input!` to be able to parse. + +#[cfg(any(feature = "full", feature = "derive"))] +use crate::AttributeArgs; + +#[cfg(any(feature = "full", feature = "derive"))] +impl ParseMacroInput for AttributeArgs { + fn parse(input: ParseStream) -> Result<Self> { + let mut metas = Vec::new(); + + loop { + if input.is_empty() { + break; + } + let value = input.parse()?; + metas.push(value); + if input.is_empty() { + break; + } + input.parse::<Token![,]>()?; + } + + Ok(metas) + } +} |