[−][src]Struct syn::parse::StepCursor
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::Result;
use syn::parse::ParseStream;
// 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"))
})
}
#
# fn remainder_after_skipping_past_next_at(
# input: ParseStream,
# ) -> Result<proc_macro2::TokenStream> {
# skip_past_next_at(input)?;
# input.parse()
# }
#
# fn main() {
# use syn::parse::Parser;
# let remainder = remainder_after_skipping_past_next_at
# .parse_str("a @ b c")
# .unwrap();
# assert_eq!(remainder.to_string(), "b c");
# }
Methods
impl<'c, 'a> StepCursor<'c, 'a>
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impl<'c, 'a> StepCursor<'c, 'a>
pub fn error<T: Display>(self, message: T) -> Error
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pub fn error<T: Display>(self, message: T) -> Error
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> Copy for StepCursor<'c, 'a>
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impl<'c, 'a> Copy for StepCursor<'c, 'a>
impl<'c, 'a> Clone for StepCursor<'c, 'a>
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impl<'c, 'a> Clone for StepCursor<'c, 'a>
fn clone(&self) -> StepCursor<'c, 'a>
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fn clone(&self) -> StepCursor<'c, 'a>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
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fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
impl<'c, 'a> Deref for StepCursor<'c, 'a>
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impl<'c, 'a> Deref for StepCursor<'c, 'a>
Auto Trait Implementations
impl<'c, 'a> !Send for StepCursor<'c, 'a>
impl<'c, 'a> !Send for StepCursor<'c, 'a>
impl<'c, 'a> !Sync for StepCursor<'c, 'a>
impl<'c, 'a> !Sync for StepCursor<'c, 'a>
Blanket Implementations
impl<T, U> Into for T where
U: From<T>,
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impl<T, U> Into for T where
U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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impl<T> ToOwned for T where
T: Clone,
type Owned = T
fn to_owned(&self) -> T
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fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
fn clone_into(&self, target: &mut T)
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fn clone_into(&self, target: &mut T)
🔬 This is a nightly-only experimental API. (toowned_clone_into
)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
impl<T> From for T
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impl<T> From for T
impl<T, U> TryFrom for T where
T: From<U>,
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impl<T, U> TryFrom for T where
T: From<U>,
type Error = !
try_from
)The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
try_from
)Performs the conversion.
impl<T> Borrow for T where
T: ?Sized,
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impl<T> Borrow for T where
T: ?Sized,
impl<T, U> TryInto for T where
U: TryFrom<T>,
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impl<T, U> TryInto for T where
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
try_from
)The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
try_from
)Performs the conversion.
impl<T> BorrowMut for T where
T: ?Sized,
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impl<T> BorrowMut for T where
T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
impl<T> Any for T where
T: 'static + ?Sized,
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impl<T> Any for T where
T: 'static + ?Sized,
fn get_type_id(&self) -> TypeId
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fn get_type_id(&self) -> TypeId
🔬 This is a nightly-only experimental API. (get_type_id
)
this method will likely be replaced by an associated static
Gets the TypeId
of self
. Read more
impl<E> SpecializationError for E
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impl<E> SpecializationError for E
fn not_found<S, T>(trait_name: &'static str, method_name: &'static str) -> E where
T: ?Sized,
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fn not_found<S, T>(trait_name: &'static str, method_name: &'static str) -> E where
T: ?Sized,
🔬 This is a nightly-only experimental API. (rustc_private
)
this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml
instead?
Create an error for a missing method specialization. Defaults to panicking with type, trait & method names. S
is the encoder/decoder state type, T
is the type being encoded/decoded, and the arguments are the names of the trait and method that should've been overridden. Read more
impl<T> Erased for T
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impl<T> Erased for T
impl<T> Send for T where
T: ?Sized,
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impl<T> Send for T where
T: ?Sized,
impl<T> Sync for T where
T: ?Sized,
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impl<T> Sync for T where
T: ?Sized,
impl<T> Erased for T
impl<T> Erased for T