[][src]Struct syn::parse::StepCursor

pub struct StepCursor<'c, 'a> { /* fields omitted */ }

Cursor state associated with speculative parsing.

This type is the input of the closure provided to ParseStream::step.

Example

use proc_macro2::TokenTree;
use syn::parse::{ParseStream, Result};

// This function advances the stream past the next occurrence of `@`. If
// no `@` is present in the stream, the stream position is unchanged and
// an error is returned.
fn skip_past_next_at(input: ParseStream) -> Result<()> {
    input.step(|cursor| {
        let mut rest = *cursor;
        while let Some((tt, next)) = rest.token_tree() {
            match tt {
                TokenTree::Punct(ref punct) if punct.as_char() == '@' => {
                    return Ok(((), next));
                }
                _ => rest = next,
            }
        }
        Err(cursor.error("no `@` was found after this point"))
    })
}

Methods

impl<'c, 'a> StepCursor<'c, 'a>
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Triggers an error at the current position of the parse stream.

The ParseStream::step invocation will return this same error without advancing the stream state.

Methods from Deref<Target = Cursor<'c>>

Trait Implementations

impl<'c, 'a> Clone for StepCursor<'c, 'a>
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Performs copy-assignment from source. Read more

impl<'c, 'a> Copy for StepCursor<'c, 'a>
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impl<'c, 'a> Deref for StepCursor<'c, 'a>
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The resulting type after dereferencing.

Auto Trait Implementations

impl<'c, 'a> !Send for StepCursor<'c, 'a>

impl<'c, 'a> !Sync for StepCursor<'c, 'a>

Blanket Implementations

impl<T> From for T
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impl<T, U> Into for T where
    U: From<T>, 
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impl<T> ToOwned for T where
    T: Clone
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impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

impl<T> Borrow for T where
    T: ?Sized
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impl<T> Any for T where
    T: 'static + ?Sized
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impl<T> BorrowMut for T where
    T: ?Sized
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impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.