[−][src]Struct syn::Error
Error returned when a Syn parser cannot parse the input tokens.
Refer to the module documentation for details about parsing in Syn.
This type is available if Syn is built with the "parsing"
feature.
Methods
impl Error
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impl Error
pub fn new<T: Display>(span: Span, message: T) -> Self
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pub fn new<T: Display>(span: Span, message: T) -> Self
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.
Example
#[macro_use] extern crate syn; use syn::{Error, Ident, LitStr, Result}; 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_spanned<T: ToTokens, U: Display>(tokens: T, message: U) -> Self
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pub fn new_spanned<T: ToTokens, U: Display>(tokens: T, message: U) -> Self
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
)!
pub fn span(&self) -> Span
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pub fn span(&self) -> Span
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 to_compile_error(&self) -> TokenStream
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pub fn to_compile_error(&self) -> TokenStream
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.
Trait Implementations
impl Clone for Error
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impl Clone for Error
fn clone(&self) -> Self
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fn clone(&self) -> Self
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0[src]
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
impl From<LexError> for Error
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impl From<LexError> for Error
impl Display for Error
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impl Display for Error
fn fmt(&self, formatter: &mut Formatter) -> Result
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fn fmt(&self, formatter: &mut Formatter) -> Result
Formats the value using the given formatter. Read more
impl Debug for Error
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impl Debug for Error
fn fmt(&self, f: &mut Formatter) -> Result
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fn fmt(&self, f: &mut Formatter) -> Result
Formats the value using the given formatter. Read more
impl Error for Error
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impl Error for Error
fn description(&self) -> &str
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fn description(&self) -> &str
This method is soft-deprecated. Read more
fn cause(&self) -> Option<&dyn Error>
1.0.0[src]
fn cause(&self) -> Option<&dyn Error>
: replaced by Error::source, which can support downcasting
The lower-level cause of this error, if any. Read more
fn source(&self) -> Option<&(dyn Error + 'static)>
1.30.0[src]
fn source(&self) -> Option<&(dyn Error + 'static)>
The lower-level source of this error, if any. Read more
Auto Trait Implementations
Blanket Implementations
impl<T> From for T
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impl<T> From for T
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> ToString for T where
T: Display + ?Sized,
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impl<T> ToString for T where
T: Display + ?Sized,
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, 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> 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, 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> 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
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impl<T> Erased for T