Struct Ident

pub struct Ident {
    pub span: Span,
    pub sym: JsWord,
    pub optional: bool,
}

A complete identifier with span.

Identifier of swc consists of two parts. The first one is symbol, which is stored using an interned string, JsWord . The second one is SyntaxContext, which can be used to distinguish identifier with same symbol.

Let me explain this with an example.

let a = 5
{
    let a = 3;
}

In the code above, there are two variables with the symbol a.

Other compilers typically uses type like Scope, and store them nested, but in rust, type like Scope requires [Arc<Mutex>] so swc uses different approach. Instead of passing scopes, swc annotates two variables with different tag, which is named SyntaxContext. The notation for the syntax context is #n where n is a number. e.g. foo#1

For the example above, after applying resolver pass, it becomes.

let a#1 = 5
{
    let a#2 = 3;
}

Thanks to the tag we attached, we can now distinguish them.

(JsWord, SyntaxContext)

See Id, which is a type alias for this.

This can be used to store all variables in a module to single hash map.

Comparison

While comparing two identifiers, you can use .to_id().

HashMap

There’s a type named Id which only contains minimal information to distinguish identifiers.

Fields

span: Span

sym: JsWord

optional: bool

TypeScript only. Used in case of an optional parameter.

Implementations

impl Ident

pub fn within_ignored_ctxt<F, Ret>(op: F) -> Ret

where F: FnOnce() -> Ret,

In op, EqIgnoreSpan of Ident will ignore the syntax context.

pub fn without_loc(self) -> Ident

Preserve syntax context while drop span.lo and span.hi.

pub fn to_id(&self) -> Id

Creates Id using JsWord and SyntaxContext of self.

pub fn is_valid_start(c: char) -> bool

Returns true if c is a valid character for an identifier start.

pub fn is_valid_continue(c: char) -> bool

Returns true if c is a valid character for an identifier part after start.

pub fn verify_symbol(s: &str) -> Result<(), String>

Alternative for toIdentifier of babel.

Returns Ok if it’s a valid identifier and Err if it’s not valid. The returned Err contains the valid symbol.

pub fn is_dummy(&self) -> bool

impl Ident

pub const fn new(sym: JsWord, span: Span) -> Self

Trait Implementations

impl AsRef<str> for Ident

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.

impl AstNode for Ident

const TYPE: &'static str = "Identifier"

impl Clone for Ident

fn clone(&self) -> Ident

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Ident

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Ident

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for Ident

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

Formats the value using the given formatter.

impl EqIgnoreSpan for Ident

fn eq_ignore_span(&self, other: &Self) -> bool

impl From<(Atom<JsWordStaticSet>, SyntaxContext)> for Ident

fn from(id: Id) -> Self

Converts to this type from the input type.

impl From<Ident> for Id

fn from(i: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for BindingIdent

fn from(id: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for Box<Expr>

fn from(src: Ident) -> Box<Expr>

Converts to this type from the input type.

impl From<Ident> for Box<Pat>

fn from(src: Ident) -> Box<Pat>

Converts to this type from the input type.

impl From<Ident> for Expr

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for JSXAttrName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for JSXElementName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for JSXObject

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for MemberProp

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for ModuleExportName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for Param

fn from(src: Ident) -> Param

Converts to this type from the input type.

impl From<Ident> for Pat

fn from(src: Ident) -> Pat

Converts to this type from the input type.

impl From<Ident> for PatOrExpr

fn from(src: Ident) -> PatOrExpr

Converts to this type from the input type.

impl From<Ident> for Prop

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for PropName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for SuperProp

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for TsEntityName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for TsEnumMemberId

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for TsModuleName

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl From<Ident> for TsThisTypeOrIdent

fn from(v: Ident) -> Self

Converts to this type from the input type.

impl Hash for Ident

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl IdentExt for Ident

fn is_reserved(&self) -> bool

fn is_reserved_in_strict_mode(&self, is_module: bool) -> bool

fn is_reserved_in_strict_bind(&self) -> bool

fn is_reserved_in_es3(&self) -> bool

impl PartialEq for Ident

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Ident

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Spanned for Ident

fn span(&self) -> Span

Get span of self.

fn span_lo(&self) -> BytePos

fn span_hi(&self) -> BytePos

impl Take for Ident

fn dummy() -> Self

Create a dummy value of this type.

fn take(&mut self) -> Self

fn map_with_mut<F>(&mut self, op: F)

where F: FnOnce(Self) -> Self,

Mutate self using op, which accepts owned data.

impl Eq for Ident

impl StructuralPartialEq for Ident