[−][src]Struct syntax::symbol::Symbol
A symbol is an interned or gensymed string. A gensym is a symbol that is never equal to any other symbol.
Conceptually, a gensym can be thought of as a normal symbol with an
invisible unique suffix. Gensyms are useful when creating new identifiers
that must not match any existing identifiers, e.g. during macro expansion
and syntax desugaring. Because gensyms should always be identifiers, all
gensym operations are on Ident
rather than Symbol
. (Indeed, in the
future the gensym-ness may be moved from Symbol
to hygiene data.)
Examples:
assert_eq!(Ident::from_str("_"), Ident::from_str("_")) assert_ne!(Ident::from_str("_").gensym_if_underscore(), Ident::from_str("_")) assert_ne!( Ident::from_str("_").gensym_if_underscore(), Ident::from_str("_").gensym_if_underscore(), )
Internally, a symbol is implemented as an index, and all operations
(including hashing, equality, and ordering) operate on that index. The use
of newtype_index!
means that Option<Symbol>
only takes up 4 bytes,
because newtype_index!
reserves the last 256 values for tagging purposes.
Note that Symbol
cannot directly be a newtype_index!
because it
implements fmt::Debug
, Encodable
, and Decodable
in special ways.
Methods
impl Symbol
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pub fn intern(string: &str) -> Symbol
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Maps a string to its interned representation.
pub fn with<F, R>(self, f: F) -> R where
F: FnOnce(&str) -> R,
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F: FnOnce(&str) -> R,
Access the symbol's chars. This is a slowish operation because it requires locking the symbol interner.
pub fn as_str(self) -> LocalInternedString
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Convert to a LocalInternedString
. This is a slowish operation because
it requires locking the symbol interner.
pub fn as_interned_str(self) -> InternedString
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Convert to an InternedString
. This is a slowish operation because it
requires locking the symbol interner.
pub fn as_u32(self) -> u32
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impl Symbol
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pub fn is_doc_keyword(self) -> bool
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Used for sanity checking rustdoc keyword sections.
pub fn is_path_segment_keyword(self) -> bool
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A keyword or reserved identifier that can be used as a path segment.
pub fn is_bool_lit(self) -> bool
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Returns true
if the symbol is true
or false
.
pub fn can_be_raw(self) -> bool
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This symbol can be a raw identifier.
Trait Implementations
impl Display for Symbol
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impl Eq for Symbol
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impl Ord for Symbol
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fn cmp(&self, other: &Symbol) -> Ordering
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fn max(self, other: Self) -> Self
1.21.0[src]
fn min(self, other: Self) -> Self
1.21.0[src]
fn clamp(self, min: Self, max: Self) -> Self
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impl PartialOrd<Symbol> for Symbol
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fn partial_cmp(&self, other: &Symbol) -> Option<Ordering>
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fn lt(&self, other: &Symbol) -> bool
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fn le(&self, other: &Symbol) -> bool
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fn gt(&self, other: &Symbol) -> bool
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fn ge(&self, other: &Symbol) -> bool
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impl Encodable for Symbol
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impl Decodable for Symbol
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impl Clone for Symbol
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impl Debug for Symbol
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impl Hash for Symbol
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fn hash<__H>(&self, state: &mut __H) where
__H: Hasher,
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__H: Hasher,
fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
1.3.0[src]
H: Hasher,
impl Copy for Symbol
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impl PartialEq<Symbol> for Symbol
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impl PartialEq<Symbol> for Path
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Auto Trait Implementations
impl Send for Symbol
impl Unpin for Symbol
impl Sync for Symbol
impl UnwindSafe for Symbol
impl RefUnwindSafe for Symbol
Blanket Implementations
impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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fn clone_into(&self, target: &mut T)
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impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
impl<T> From<T> for T
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
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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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
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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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Erased for T
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impl<T> Encodable for T where
T: UseSpecializedEncodable + ?Sized,
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T: UseSpecializedEncodable + ?Sized,
impl<T> Decodable for T where
T: UseSpecializedDecodable,
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T: UseSpecializedDecodable,
impl<E> SpecializationError for E
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default fn not_found<S, T>(
trait_name: &'static str,
method_name: &'static str
) -> E where
T: ?Sized,
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trait_name: &'static str,
method_name: &'static str
) -> E where
T: ?Sized,
impl<Q, K> Equivalent<K> for Q where
K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,
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K: Borrow<Q> + ?Sized,
Q: Eq + ?Sized,