Struct syntax_pos::symbol::Symbol

pub struct 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

pub fn intern(string: &str) -> Self

Maps a string to its interned representation.

pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R

Access the symbol's chars. This is a slowish operation because it requires locking the symbol interner.

pub fn as_str(self) -> LocalInternedString

Convert to a LocalInternedString. This is a slowish operation because it requires locking the symbol interner.

pub fn as_interned_str(self) -> InternedString

Convert to an InternedString. This is a slowish operation because it requires locking the symbol interner.

pub fn as_u32(self) -> u32

impl Symbol

pub fn is_doc_keyword(self) -> bool

Used for sanity checking rustdoc keyword sections.

pub fn is_path_segment_keyword(self) -> bool

A keyword or reserved identifier that can be used as a path segment.

pub fn is_bool_lit(self) -> bool

Returns true if the symbol is true or false.

pub fn can_be_raw(self) -> bool

This symbol can be a raw identifier.

Trait Implementations

impl Eq for Symbol

impl Clone for Symbol

fn clone(&self) -> Symbol

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl PartialOrd<Symbol> for Symbol

fn partial_cmp(&self, other: &Symbol) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Symbol) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Symbol) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Symbol) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Symbol) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Ord for Symbol

fn cmp(&self, other: &Symbol) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl PartialEq<Symbol> for Symbol

fn eq(&self, other: &Symbol) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Symbol) -> bool

This method tests for !=.

impl Copy for Symbol

impl Hash for Symbol

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Display for Symbol

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Debug for Symbol

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Encodable for Symbol

fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error>

impl Decodable for Symbol

fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error>