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Diffstat (limited to 'vendor/syn/src/lookahead.rs')
-rw-r--r-- | vendor/syn/src/lookahead.rs | 169 |
1 files changed, 0 insertions, 169 deletions
diff --git a/vendor/syn/src/lookahead.rs b/vendor/syn/src/lookahead.rs deleted file mode 100644 index e89a4c7..0000000 --- a/vendor/syn/src/lookahead.rs +++ /dev/null @@ -1,169 +0,0 @@ -use crate::buffer::Cursor; -use crate::error::{self, Error}; -use crate::sealed::lookahead::Sealed; -use crate::span::IntoSpans; -use crate::token::Token; -use proc_macro2::{Delimiter, Span}; -use std::cell::RefCell; - -/// Support for checking the next token in a stream to decide how to parse. -/// -/// An important advantage over [`ParseStream::peek`] is that here we -/// automatically construct an appropriate error message based on the token -/// alternatives that get peeked. If you are producing your own error message, -/// go ahead and use `ParseStream::peek` instead. -/// -/// Use [`ParseStream::lookahead1`] to construct this object. -/// -/// [`ParseStream::peek`]: crate::parse::ParseBuffer::peek -/// [`ParseStream::lookahead1`]: crate::parse::ParseBuffer::lookahead1 -/// -/// Consuming tokens from the source stream after constructing a lookahead -/// object does not also advance the lookahead object. -/// -/// # Example -/// -/// ``` -/// use syn::{ConstParam, Ident, Lifetime, LifetimeParam, Result, Token, TypeParam}; -/// use syn::parse::{Parse, ParseStream}; -/// -/// // A generic parameter, a single one of the comma-separated elements inside -/// // angle brackets in: -/// // -/// // fn f<T: Clone, 'a, 'b: 'a, const N: usize>() { ... } -/// // -/// // On invalid input, lookahead gives us a reasonable error message. -/// // -/// // error: expected one of: identifier, lifetime, `const` -/// // | -/// // 5 | fn f<!Sized>() {} -/// // | ^ -/// enum GenericParam { -/// Type(TypeParam), -/// Lifetime(LifetimeParam), -/// Const(ConstParam), -/// } -/// -/// impl Parse for GenericParam { -/// fn parse(input: ParseStream) -> Result<Self> { -/// let lookahead = input.lookahead1(); -/// if lookahead.peek(Ident) { -/// input.parse().map(GenericParam::Type) -/// } else if lookahead.peek(Lifetime) { -/// input.parse().map(GenericParam::Lifetime) -/// } else if lookahead.peek(Token![const]) { -/// input.parse().map(GenericParam::Const) -/// } else { -/// Err(lookahead.error()) -/// } -/// } -/// } -/// ``` -pub struct Lookahead1<'a> { - scope: Span, - cursor: Cursor<'a>, - comparisons: RefCell<Vec<&'static str>>, -} - -pub(crate) fn new(scope: Span, cursor: Cursor) -> Lookahead1 { - Lookahead1 { - scope, - cursor, - comparisons: RefCell::new(Vec::new()), - } -} - -fn peek_impl( - lookahead: &Lookahead1, - peek: fn(Cursor) -> bool, - display: fn() -> &'static str, -) -> bool { - if peek(lookahead.cursor) { - return true; - } - lookahead.comparisons.borrow_mut().push(display()); - false -} - -impl<'a> Lookahead1<'a> { - /// Looks at the next token in the parse stream to determine whether it - /// matches the requested type of token. - /// - /// # Syntax - /// - /// Note that this method does not use turbofish syntax. Pass the peek type - /// inside of parentheses. - /// - /// - `input.peek(Token![struct])` - /// - `input.peek(Token![==])` - /// - `input.peek(Ident)` *(does not accept keywords)* - /// - `input.peek(Ident::peek_any)` - /// - `input.peek(Lifetime)` - /// - `input.peek(token::Brace)` - pub fn peek<T: Peek>(&self, token: T) -> bool { - let _ = token; - peek_impl(self, T::Token::peek, T::Token::display) - } - - /// Triggers an error at the current position of the parse stream. - /// - /// The error message will identify all of the expected token types that - /// have been peeked against this lookahead instance. - pub fn error(self) -> Error { - let comparisons = self.comparisons.borrow(); - match comparisons.len() { - 0 => { - if self.cursor.eof() { - Error::new(self.scope, "unexpected end of input") - } else { - Error::new(self.cursor.span(), "unexpected token") - } - } - 1 => { - let message = format!("expected {}", comparisons[0]); - error::new_at(self.scope, self.cursor, message) - } - 2 => { - let message = format!("expected {} or {}", comparisons[0], comparisons[1]); - error::new_at(self.scope, self.cursor, message) - } - _ => { - let join = comparisons.join(", "); - let message = format!("expected one of: {}", join); - error::new_at(self.scope, self.cursor, message) - } - } - } -} - -/// Types that can be parsed by looking at just one token. -/// -/// Use [`ParseStream::peek`] to peek one of these types in a parse stream -/// without consuming it from the stream. -/// -/// This trait is sealed and cannot be implemented for types outside of Syn. -/// -/// [`ParseStream::peek`]: crate::parse::ParseBuffer::peek -pub trait Peek: Sealed { - // Not public API. - #[doc(hidden)] - type Token: Token; -} - -impl<F: Copy + FnOnce(TokenMarker) -> T, T: Token> Peek for F { - type Token = T; -} - -pub enum TokenMarker {} - -impl<S> IntoSpans<S> for TokenMarker { - fn into_spans(self) -> S { - match self {} - } -} - -pub(crate) fn is_delimiter(cursor: Cursor, delimiter: Delimiter) -> bool { - cursor.group(delimiter).is_some() -} - -impl<F: Copy + FnOnce(TokenMarker) -> T, T: Token> Sealed for F {} |