perf(es/lexer): Optimize lexer (#9075)

**Description:**

 - `TokenContext` is now 1 byte.
 - `read_word_with` now uses `&dyn` instead of `impl FnOnce`.

crates/swc_ecma_parser/src/lexer/mod.rs

@@ -754,7 +754,7 @@ impl<'a> Lexer<'a> {
     /// character.
     fn read_word_with(
         &mut self,
-        convert: impl FnOnce(&str) -> Option<Word>,
+        convert: &dyn Fn(&str) -> Option<Word>,
     ) -> LexResult<Option<Token>> {
         debug_assert!(self.cur().is_some());
 

crates/swc_ecma_parser/src/lexer/state.rs

@@ -32,6 +32,7 @@ pub(super) struct State {
     pub cur_line: usize,
     pub line_start: BytePos,
     pub prev_hi: BytePos,
+    pub tpl_start: BytePos,
 
     context: TokenContexts,
     syntax: Syntax,
@@ -323,11 +324,9 @@ impl<'a> Iterator for Lexer<'a> {
                 }
             }
 
-            if let Some(TokenContext::Tpl {
-                start: start_pos_of_tpl,
-            }) = self.state.context.current()
-            {
-                return self.read_tmpl_token(start_pos_of_tpl).map(Some);
+            if let Some(TokenContext::Tpl {}) = self.state.context.current() {
+                let start = self.state.tpl_start;
+                return self.read_tmpl_token(start).map(Some);
             }
 
             self.read_token()
@@ -373,16 +372,17 @@ impl State {
         State {
             is_expr_allowed: true,
             next_regexp: None,
-            is_first: true,
             had_line_break: false,
             had_line_break_before_last: false,
-            prev_hi: start_pos,
-            context,
-            token_type: None,
+            is_first: true,
             start: BytePos(0),
-            line_start: BytePos(0),
             cur_line: 1,
+            line_start: BytePos(0),
+            prev_hi: start_pos,
+            tpl_start: BytePos::DUMMY,
+            context,
             syntax,
+            token_type: None,
         }
     }
 }
@@ -431,30 +431,26 @@ impl State {
         let prev = self.token_type.take();
         self.token_type = Some(TokenType::from(next));
 
-        self.is_expr_allowed = Self::is_expr_allowed_on_next(
-            &mut self.context,
-            self.syntax,
-            prev,
-            start,
-            next,
-            self.had_line_break,
-            self.had_line_break_before_last,
-            self.is_expr_allowed,
-        );
+        self.is_expr_allowed = self.is_expr_allowed_on_next(prev, start, next);
     }
 
     /// `is_expr_allowed`: previous value.
     /// `start`: start of newly produced token.
     fn is_expr_allowed_on_next(
-        context: &mut TokenContexts,
-        syntax: Syntax,
+        &mut self,
         prev: Option<TokenType>,
         start: BytePos,
         next: TokenKind,
-        had_line_break: bool,
-        had_line_break_before_last: bool,
-        is_expr_allowed: bool,
     ) -> bool {
+        let State {
+            ref mut context,
+            had_line_break,
+            had_line_break_before_last,
+            is_expr_allowed,
+            syntax,
+            ..
+        } = *self;
+
         let is_next_keyword = matches!(next, TokenKind::Word(WordKind::Keyword(..)));
 
         if is_next_keyword && prev == Some(TokenType::Dot) {
@@ -612,7 +608,8 @@ impl State {
                     if let Some(TokenContext::Tpl { .. }) = context.current() {
                         context.pop();
                     } else {
-                        context.push(TokenContext::Tpl { start });
+                        self.tpl_start = start;
+                        context.push(TokenContext::Tpl);
                     }
                     false
                 }
@@ -761,7 +758,6 @@ impl TokenContexts {
 /// The algorithm used to determine whether a regexp can appear at a
 /// given point in the program is loosely based on sweet.js' approach.
 /// See https://github.com/mozilla/sweet.js/wiki/design
-#[repr(u8)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum TokenContext {
     BraceStmt,
@@ -772,10 +768,7 @@ pub enum TokenContext {
         is_for_loop: bool,
     },
     ParenExpr,
-    Tpl {
-        /// Start of a template literal.
-        start: BytePos,
-    },
+    Tpl,
     FnExpr,
     ClassExpr,
     JSXOpeningTag,

crates/swc_ecma_parser/src/lexer/table.rs

@@ -63,7 +63,7 @@ const ERR: ByteHandler = Some(|lexer| {
 const IDN: ByteHandler = Some(|lexer| lexer.read_ident_unknown().map(Some));
 
 const L_A: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "abstract" => Some(Word::Ident(IdentLike::Known(KnownIdent::Abstract))),
         "as" => Some(Word::Ident(IdentLike::Known(KnownIdent::As))),
         "await" => Some(Word::Keyword(Keyword::Await)),
@@ -77,7 +77,7 @@ const L_A: ByteHandler = Some(|lexer| {
 });
 
 const L_B: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "break" => Some(Word::Keyword(Keyword::Break)),
         "boolean" => Some(Word::Ident(IdentLike::Known(KnownIdent::Boolean))),
         "bigint" => Some(Word::Ident(IdentLike::Known(KnownIdent::Bigint))),
@@ -86,7 +86,7 @@ const L_B: ByteHandler = Some(|lexer| {
 });
 
 const L_C: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "case" => Some(Word::Keyword(Keyword::Case)),
         "catch" => Some(Word::Keyword(Keyword::Catch)),
         "class" => Some(Word::Keyword(Keyword::Class)),
@@ -97,7 +97,7 @@ const L_C: ByteHandler = Some(|lexer| {
 });
 
 const L_D: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "debugger" => Some(Word::Keyword(Keyword::Debugger)),
         "default" => Some(Word::Keyword(Keyword::Default_)),
         "delete" => Some(Word::Keyword(Keyword::Delete)),
@@ -108,7 +108,7 @@ const L_D: ByteHandler = Some(|lexer| {
 });
 
 const L_E: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "else" => Some(Word::Keyword(Keyword::Else)),
         "enum" => Some(Word::Ident(IdentLike::Known(KnownIdent::Enum))),
         "export" => Some(Word::Keyword(Keyword::Export)),
@@ -118,7 +118,7 @@ const L_E: ByteHandler = Some(|lexer| {
 });
 
 const L_F: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "false" => Some(Word::False),
         "finally" => Some(Word::Keyword(Keyword::Finally)),
         "for" => Some(Word::Keyword(Keyword::For)),
@@ -129,7 +129,7 @@ const L_F: ByteHandler = Some(|lexer| {
 });
 
 const L_G: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "global" => Some(Word::Ident(IdentLike::Known(KnownIdent::Global))),
         "get" => Some(Word::Ident(IdentLike::Known(KnownIdent::Get))),
         _ => None,
@@ -139,7 +139,7 @@ const L_G: ByteHandler = Some(|lexer| {
 const L_H: ByteHandler = IDN;
 
 const L_I: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "if" => Some(Word::Keyword(Keyword::If)),
         "import" => Some(Word::Keyword(Keyword::Import)),
         "in" => Some(Word::Keyword(Keyword::In)),
@@ -156,28 +156,28 @@ const L_I: ByteHandler = Some(|lexer| {
 const L_J: ByteHandler = IDN;
 
 const L_K: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "keyof" => Some(Word::Ident(IdentLike::Known(KnownIdent::Keyof))),
         _ => None,
     })
 });
 
 const L_L: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "let" => Some(Word::Keyword(Keyword::Let)),
         _ => None,
     })
 });
 
 const L_M: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "meta" => Some(Word::Ident(IdentLike::Known(KnownIdent::Meta))),
         _ => None,
     })
 });
 
 const L_N: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "new" => Some(Word::Keyword(Keyword::New)),
         "null" => Some(Word::Null),
         "number" => Some(Word::Ident(IdentLike::Known(KnownIdent::Number))),
@@ -188,15 +188,15 @@ const L_N: ByteHandler = Some(|lexer| {
 });
 
 const L_O: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "of" => Some(Word::Ident(IdentLike::Known(KnownIdent::Of))),
         "object" => Some(Word::Ident(IdentLike::Known(KnownIdent::Object))),
         _ => None,
     })
 });
 
 const L_P: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "public" => Some(Word::Ident(IdentLike::Known(KnownIdent::Public))),
         "package" => Some(Word::Ident(IdentLike::Known(KnownIdent::Package))),
         "protected" => Some(Word::Ident(IdentLike::Known(KnownIdent::Protected))),
@@ -208,7 +208,7 @@ const L_P: ByteHandler = Some(|lexer| {
 const L_Q: ByteHandler = IDN;
 
 const L_R: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "return" => Some(Word::Keyword(Keyword::Return)),
         "readonly" => Some(Word::Ident(IdentLike::Known(KnownIdent::Readonly))),
         "require" => Some(Word::Ident(IdentLike::Known(KnownIdent::Require))),
@@ -217,7 +217,7 @@ const L_R: ByteHandler = Some(|lexer| {
 });
 
 const L_S: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "super" => Some(Word::Keyword(Keyword::Super)),
         "static" => Some(Word::Ident(IdentLike::Known(KnownIdent::Static))),
         "switch" => Some(Word::Keyword(Keyword::Switch)),
@@ -230,7 +230,7 @@ const L_S: ByteHandler = Some(|lexer| {
 });
 
 const L_T: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "this" => Some(Word::Keyword(Keyword::This)),
         "throw" => Some(Word::Keyword(Keyword::Throw)),
         "true" => Some(Word::True),
@@ -243,7 +243,7 @@ const L_T: ByteHandler = Some(|lexer| {
 });
 
 const L_U: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "using" => Some(Word::Ident(IdentLike::Known(KnownIdent::Using))),
         "unique" => Some(Word::Ident(IdentLike::Known(KnownIdent::Unique))),
         "undefined" => Some(Word::Ident(IdentLike::Known(KnownIdent::Undefined))),
@@ -253,15 +253,15 @@ const L_U: ByteHandler = Some(|lexer| {
 });
 
 const L_V: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "var" => Some(Word::Keyword(Keyword::Var)),
         "void" => Some(Word::Keyword(Keyword::Void)),
         _ => None,
     })
 });
 
 const L_W: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "while" => Some(Word::Keyword(Keyword::While)),
         "with" => Some(Word::Keyword(Keyword::With)),
         _ => None,
@@ -271,7 +271,7 @@ const L_W: ByteHandler = Some(|lexer| {
 const L_X: ByteHandler = IDN;
 
 const L_Y: ByteHandler = Some(|lexer| {
-    lexer.read_word_with(|s| match s {
+    lexer.read_word_with(&|s| match s {
         "yield" => Some(Word::Keyword(Keyword::Yield)),
         _ => None,
     })