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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#[cfg(feature = "parsing")]use crate::buffer::Cursor;use crate::thread::ThreadBound;use proc_macro2::{ Delimiter, Group, Ident, LexError, Literal, Punct, Spacing, Span, TokenStream, TokenTree,};#[cfg(feature = "printing")]use quote::ToTokens;use std::fmt::{self, Debug, Display};use std::slice;use std::vec;
/// The result of a Syn parser.pub type Result<T> = std::result::Result<T, Error>;
/// Error returned when a Syn parser cannot parse the input tokens.////// # Error reporting in proc macros////// The correct way to report errors back to the compiler from a procedural/// macro is by emitting an appropriately spanned invocation of/// [`compile_error!`] in the generated code. This produces a better diagnostic/// message than simply panicking the macro.////// [`compile_error!`]: std::compile_error!////// When parsing macro input, the [`parse_macro_input!`] macro handles the/// conversion to `compile_error!` automatically.////// [`parse_macro_input!`]: crate::parse_macro_input!////// ```/// # extern crate proc_macro;/// #/// use proc_macro::TokenStream;/// use syn::parse::{Parse, ParseStream, Result};/// use syn::{parse_macro_input, ItemFn};////// # const IGNORE: &str = stringify! {/// #[proc_macro_attribute]/// # };/// pub fn my_attr(args: TokenStream, input: TokenStream) -> TokenStream {/// let args = parse_macro_input!(args as MyAttrArgs);/// let input = parse_macro_input!(input as ItemFn);////// /* ... *//// # TokenStream::new()/// }////// struct MyAttrArgs {/// # _k: [(); { stringify! {/// .../// # }; 0 }]/// }////// impl Parse for MyAttrArgs {/// fn parse(input: ParseStream) -> Result<Self> {/// # stringify! {/// .../// # };/// # unimplemented!()/// }/// }/// ```////// For errors that arise later than the initial parsing stage, the/// [`.to_compile_error()`] or [`.into_compile_error()`] methods can be used to/// perform an explicit conversion to `compile_error!`.////// [`.to_compile_error()`]: Error::to_compile_error/// [`.into_compile_error()`]: Error::into_compile_error////// ```/// # extern crate proc_macro;/// #/// # use proc_macro::TokenStream;/// # use syn::{parse_macro_input, DeriveInput};/// #/// # const IGNORE: &str = stringify! {/// #[proc_macro_derive(MyDerive)]/// # };/// pub fn my_derive(input: TokenStream) -> TokenStream {/// let input = parse_macro_input!(input as DeriveInput);////// // fn(DeriveInput) -> syn::Result<proc_macro2::TokenStream>/// expand::my_derive(input)/// .unwrap_or_else(syn::Error::into_compile_error)/// .into()/// }/// #/// # mod expand {/// # use proc_macro2::TokenStream;/// # use syn::{DeriveInput, Result};/// #/// # pub fn my_derive(input: DeriveInput) -> Result<TokenStream> {/// # unimplemented!()/// # }/// # }/// ```pub struct Error { messages: Vec<ErrorMessage>,}
struct ErrorMessage { // Span is implemented as an index into a thread-local interner to keep the // size small. It is not safe to access from a different thread. We want // errors to be Send and Sync to play nicely with ecosystem crates for error // handling, so pin the span we're given to its original thread and assume // it is Span::call_site if accessed from any other thread. span: ThreadBound<SpanRange>, message: String,}
// Cannot use std::ops::Range<Span> because that does not implement Copy,// whereas ThreadBound<T> requires a Copy impl as a way to ensure no Drop impls// are involved.struct SpanRange { start: Span, end: Span,}
#[cfg(test)]struct _Testwhere Error: Send + Sync;
impl Error { /// Usually the [`ParseStream::error`] method will be used instead, which /// automatically uses the correct span from the current position of the /// parse stream. /// /// Use `Error::new` when the error needs to be triggered on some span other /// than where the parse stream is currently positioned. /// /// [`ParseStream::error`]: crate::parse::ParseBuffer::error /// /// # Example /// /// ``` /// use syn::{Error, Ident, LitStr, Result, Token}; /// use syn::parse::ParseStream; /// /// // Parses input that looks like `name = "string"` where the key must be /// // the identifier `name` and the value may be any string literal. /// // Returns the string literal. /// fn parse_name(input: ParseStream) -> Result<LitStr> { /// let name_token: Ident = input.parse()?; /// if name_token != "name" { /// // Trigger an error not on the current position of the stream, /// // but on the position of the unexpected identifier. /// return Err(Error::new(name_token.span(), "expected `name`")); /// } /// input.parse::<Token![=]>()?; /// let s: LitStr = input.parse()?; /// Ok(s) /// } /// ``` pub fn new<T: Display>(span: Span, message: T) -> Self { return new(span, message.to_string());
fn new(span: Span, message: String) -> Error { Error { messages: vec![ErrorMessage { span: ThreadBound::new(SpanRange { start: span, end: span, }), message, }], } } }
/// Creates an error with the specified message spanning the given syntax /// tree node. /// /// Unlike the `Error::new` constructor, this constructor takes an argument /// `tokens` which is a syntax tree node. This allows the resulting `Error` /// to attempt to span all tokens inside of `tokens`. While you would /// typically be able to use the `Spanned` trait with the above `Error::new` /// constructor, implementation limitations today mean that /// `Error::new_spanned` may provide a higher-quality error message on /// stable Rust. /// /// When in doubt it's recommended to stick to `Error::new` (or /// `ParseStream::error`)! #[cfg(feature = "printing")] #[cfg_attr(docsrs, doc(cfg(feature = "printing")))] pub fn new_spanned<T: ToTokens, U: Display>(tokens: T, message: U) -> Self { return new_spanned(tokens.into_token_stream(), message.to_string());
fn new_spanned(tokens: TokenStream, message: String) -> Error { let mut iter = tokens.into_iter(); let start = iter.next().map_or_else(Span::call_site, |t| t.span()); let end = iter.last().map_or(start, |t| t.span()); Error { messages: vec![ErrorMessage { span: ThreadBound::new(SpanRange { start, end }), message, }], } } }
/// The source location of the error. /// /// Spans are not thread-safe so this function returns `Span::call_site()` /// if called from a different thread than the one on which the `Error` was /// originally created. pub fn span(&self) -> Span { let SpanRange { start, end } = match self.messages[0].span.get() { Some(span) => *span, None => return Span::call_site(), }; start.join(end).unwrap_or(start) }
/// Render the error as an invocation of [`compile_error!`]. /// /// The [`parse_macro_input!`] macro provides a convenient way to invoke /// this method correctly in a procedural macro. /// /// [`compile_error!`]: std::compile_error! /// [`parse_macro_input!`]: crate::parse_macro_input! pub fn to_compile_error(&self) -> TokenStream { self.messages .iter() .map(ErrorMessage::to_compile_error) .collect() }
/// Render the error as an invocation of [`compile_error!`]. /// /// [`compile_error!`]: std::compile_error! /// /// # Example /// /// ``` /// # extern crate proc_macro; /// # /// use proc_macro::TokenStream; /// use syn::{parse_macro_input, DeriveInput, Error}; /// /// # const _: &str = stringify! { /// #[proc_macro_derive(MyTrait)] /// # }; /// pub fn derive_my_trait(input: TokenStream) -> TokenStream { /// let input = parse_macro_input!(input as DeriveInput); /// my_trait::expand(input) /// .unwrap_or_else(Error::into_compile_error) /// .into() /// } /// /// mod my_trait { /// use proc_macro2::TokenStream; /// use syn::{DeriveInput, Result}; /// /// pub(crate) fn expand(input: DeriveInput) -> Result<TokenStream> { /// /* ... */ /// # unimplemented!() /// } /// } /// ``` pub fn into_compile_error(self) -> TokenStream { self.to_compile_error() }
/// Add another error message to self such that when `to_compile_error()` is /// called, both errors will be emitted together. pub fn combine(&mut self, another: Error) { self.messages.extend(another.messages); }}
impl ErrorMessage { fn to_compile_error(&self) -> TokenStream { let (start, end) = match self.span.get() { Some(range) => (range.start, range.end), None => (Span::call_site(), Span::call_site()), };
// ::core::compile_error!($message) TokenStream::from_iter([ TokenTree::Punct({ let mut punct = Punct::new(':', Spacing::Joint); punct.set_span(start); punct }), TokenTree::Punct({ let mut punct = Punct::new(':', Spacing::Alone); punct.set_span(start); punct }), TokenTree::Ident(Ident::new("core", start)), TokenTree::Punct({ let mut punct = Punct::new(':', Spacing::Joint); punct.set_span(start); punct }), TokenTree::Punct({ let mut punct = Punct::new(':', Spacing::Alone); punct.set_span(start); punct }), TokenTree::Ident(Ident::new("compile_error", start)), TokenTree::Punct({ let mut punct = Punct::new('!', Spacing::Alone); punct.set_span(start); punct }), TokenTree::Group({ let mut group = Group::new(Delimiter::Brace, { TokenStream::from_iter([TokenTree::Literal({ let mut string = Literal::string(&self.message); string.set_span(end); string })]) }); group.set_span(end); group }), ]) }}
#[cfg(feature = "parsing")]pub(crate) fn new_at<T: Display>(scope: Span, cursor: Cursor, message: T) -> Error { if cursor.eof() { Error::new(scope, format!("unexpected end of input, {}", message)) } else { let span = crate::buffer::open_span_of_group(cursor); Error::new(span, message) }}
#[cfg(all(feature = "parsing", any(feature = "full", feature = "derive")))]pub(crate) fn new2<T: Display>(start: Span, end: Span, message: T) -> Error { return new2(start, end, message.to_string());
fn new2(start: Span, end: Span, message: String) -> Error { Error { messages: vec![ErrorMessage { span: ThreadBound::new(SpanRange { start, end }), message, }], } }}
impl Debug for Error { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { if self.messages.len() == 1 { formatter .debug_tuple("Error") .field(&self.messages[0]) .finish() } else { formatter .debug_tuple("Error") .field(&self.messages) .finish() } }}
impl Debug for ErrorMessage { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { Debug::fmt(&self.message, formatter) }}
impl Display for Error { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { formatter.write_str(&self.messages[0].message) }}
impl Clone for Error { fn clone(&self) -> Self { Error { messages: self.messages.clone(), } }}
impl Clone for ErrorMessage { fn clone(&self) -> Self { ErrorMessage { span: self.span, message: self.message.clone(), } }}
impl Clone for SpanRange { fn clone(&self) -> Self { *self }}
impl Copy for SpanRange {}
impl std::error::Error for Error {}
impl From<LexError> for Error { fn from(err: LexError) -> Self { Error::new(err.span(), err) }}
impl IntoIterator for Error { type Item = Error; type IntoIter = IntoIter;
fn into_iter(self) -> Self::IntoIter { IntoIter { messages: self.messages.into_iter(), } }}
pub struct IntoIter { messages: vec::IntoIter<ErrorMessage>,}
impl Iterator for IntoIter { type Item = Error;
fn next(&mut self) -> Option<Self::Item> { Some(Error { messages: vec![self.messages.next()?], }) }}
impl<'a> IntoIterator for &'a Error { type Item = Error; type IntoIter = Iter<'a>;
fn into_iter(self) -> Self::IntoIter { Iter { messages: self.messages.iter(), } }}
pub struct Iter<'a> { messages: slice::Iter<'a, ErrorMessage>,}
impl<'a> Iterator for Iter<'a> { type Item = Error;
fn next(&mut self) -> Option<Self::Item> { Some(Error { messages: vec![self.messages.next()?.clone()], }) }}
impl Extend<Error> for Error { fn extend<T: IntoIterator<Item = Error>>(&mut self, iter: T) { for err in iter { self.combine(err); } }}