Recognize Directive Prologues correctly (#2521)

This Pull Request changes the following:

- Recognize the `"use strict"` directive prologue correctly.
- Refactor parsers to remove a setter function.

boa_ast/src/statement_list.rs

@@ -121,6 +121,18 @@ pub struct StatementList {
 }
 
 impl StatementList {
+    /// Creates a new `StatementList` AST node.
+    #[must_use]
+    pub fn new<S>(statements: S, strict: bool) -> Self
+    where
+        S: Into<Box<[StatementListItem]>>,
+    {
+        Self {
+            statements: statements.into(),
+            strict,
+        }
+    }
+
     /// Gets the list of statements.
     #[inline]
     #[must_use]
@@ -134,12 +146,6 @@ impl StatementList {
     pub const fn strict(&self) -> bool {
         self.strict
     }
-
-    /// Set the strict mode.
-    #[inline]
-    pub fn set_strict(&mut self, strict: bool) {
-        self.strict = strict;
-    }
 }
 
 impl From<Box<[StatementListItem]>> for StatementList {

boa_parser/src/parser/function/mod.rs

@@ -26,7 +26,6 @@ use boa_ast::{
     Punctuator,
 };
 use boa_interner::{Interner, Sym};
-use boa_macros::utf16;
 use boa_profiler::Profiler;
 use std::io::Read;
 
@@ -449,41 +448,14 @@ where
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
         let _timer = Profiler::global().start_event("FunctionStatementList", "Parsing");
 
-        let global_strict_mode = cursor.strict_mode();
-        let mut strict = false;
-
-        if let Some(tk) = cursor.peek(0, interner)? {
-            match tk.kind() {
-                TokenKind::Punctuator(Punctuator::CloseBlock) => {
-                    return Ok(Vec::new().into());
-                }
-                TokenKind::StringLiteral(string)
-                    if interner.resolve_expect(*string).join(
-                        |s| s == "use strict",
-                        |g| g == utf16!("use strict"),
-                        true,
-                    ) =>
-                {
-                    cursor.set_strict_mode(true);
-                    strict = true;
-                }
-                _ => {}
-            }
-        }
-
-        let statement_list = StatementList::new(
+        StatementList::new(
             self.allow_yield,
             self.allow_await,
             true,
             &FUNCTION_BREAK_TOKENS,
+            true,
+            false,
         )
-        .parse(cursor, interner);
-
-        // Reset strict mode back to the global scope.
-        cursor.set_strict_mode(global_strict_mode);
-
-        let mut statement_list = statement_list?;
-        statement_list.set_strict(strict);
-        Ok(statement_list)
+        .parse(cursor, interner)
     }
 }

boa_parser/src/parser/mod.rs

@@ -11,7 +11,6 @@ mod tests;
 
 use crate::{
     error::ParseResult,
-    lexer::TokenKind,
     parser::{
         cursor::Cursor,
         function::{FormalParameters, FunctionStatementList},
@@ -27,7 +26,6 @@ use boa_ast::{
     Position, StatementList,
 };
 use boa_interner::Interner;
-use boa_macros::utf16;
 use rustc_hash::FxHashSet;
 use std::io::Read;
 
@@ -239,52 +237,31 @@ where
     type Output = StatementList;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let mut strict = cursor.strict_mode();
-        match cursor.peek(0, interner)? {
-            Some(tok) => {
-                match tok.kind() {
-                    // Set the strict mode
-                    TokenKind::StringLiteral(string)
-                        if interner.resolve_expect(*string).join(
-                            |s| s == "use strict",
-                            |g| g == utf16!("use strict"),
-                            true,
-                        ) =>
-                    {
-                        cursor.set_strict_mode(true);
-                        strict = true;
-                    }
-                    _ => {}
-                }
-                let mut statement_list =
-                    ScriptBody::new(self.direct_eval).parse(cursor, interner)?;
-                statement_list.set_strict(strict);
-
-                // It is a Syntax Error if the LexicallyDeclaredNames of ScriptBody contains any duplicate entries.
-                // It is a Syntax Error if any element of the LexicallyDeclaredNames of ScriptBody also occurs in the VarDeclaredNames of ScriptBody.
-                let mut lexical_names = FxHashSet::default();
-                for name in top_level_lexically_declared_names(&statement_list) {
-                    if !lexical_names.insert(name) {
-                        return Err(Error::general(
-                            "lexical name declared multiple times",
-                            Position::new(1, 1),
-                        ));
-                    }
-                }
-
-                for name in top_level_var_declared_names(&statement_list) {
-                    if lexical_names.contains(&name) {
-                        return Err(Error::general(
-                            "lexical name declared multiple times",
-                            Position::new(1, 1),
-                        ));
-                    }
-                }
-
-                Ok(statement_list)
+        let statement_list = ScriptBody::new(true, cursor.strict_mode(), self.direct_eval)
+            .parse(cursor, interner)?;
+
+        // It is a Syntax Error if the LexicallyDeclaredNames of ScriptBody contains any duplicate entries.
+        // It is a Syntax Error if any element of the LexicallyDeclaredNames of ScriptBody also occurs in the VarDeclaredNames of ScriptBody.
+        let mut lexical_names = FxHashSet::default();
+        for name in top_level_lexically_declared_names(&statement_list) {
+            if !lexical_names.insert(name) {
+                return Err(Error::general(
+                    "lexical name declared multiple times",
+                    Position::new(1, 1),
+                ));
             }
-            None => Ok(StatementList::from(Vec::new())),
         }
+
+        for name in top_level_var_declared_names(&statement_list) {
+            if lexical_names.contains(&name) {
+                return Err(Error::general(
+                    "lexical name declared multiple times",
+                    Position::new(1, 1),
+                ));
+            }
+        }
+
+        Ok(statement_list)
     }
 }
 
@@ -296,14 +273,20 @@ where
 /// [spec]: https://tc39.es/ecma262/#prod-ScriptBody
 #[derive(Debug, Clone, Copy)]
 pub struct ScriptBody {
+    directive_prologues: bool,
+    strict: bool,
     direct_eval: bool,
 }
 
 impl ScriptBody {
     /// Create a new `ScriptBody` parser.
     #[inline]
-    const fn new(direct_eval: bool) -> Self {
-        Self { direct_eval }
+    const fn new(directive_prologues: bool, strict: bool, direct_eval: bool) -> Self {
+        Self {
+            directive_prologues,
+            strict,
+            direct_eval,
+        }
     }
 }
 
@@ -314,8 +297,15 @@ where
     type Output = StatementList;
 
     fn parse(self, cursor: &mut Cursor<R>, interner: &mut Interner) -> ParseResult<Self::Output> {
-        let body = self::statement::StatementList::new(false, false, false, &[])
-            .parse(cursor, interner)?;
+        let body = self::statement::StatementList::new(
+            false,
+            false,
+            false,
+            &[],
+            self.directive_prologues,
+            self.strict,
+        )
+        .parse(cursor, interner)?;
 
         if !self.direct_eval {
             // It is a Syntax Error if StatementList Contains super unless the source text containing super is eval

boa_parser/src/parser/statement/block/mod.rs

@@ -90,6 +90,8 @@ where
             self.allow_await,
             self.allow_return,
             &BLOCK_BREAK_TOKENS,
+            false,
+            false,
         )
         .parse(cursor, interner)
         .map(statement::Block::from)?;

boa_parser/src/parser/statement/declaration/hoistable/class_decl/mod.rs

@@ -666,9 +666,15 @@ where
                     let strict = cursor.strict_mode();
                     cursor.set_strict_mode(true);
                     let position = cursor.peek(0, interner).or_abrupt()?.span().start();
-                    let statement_list =
-                        StatementList::new(false, true, false, &FUNCTION_BREAK_TOKENS)
-                            .parse(cursor, interner)?;
+                    let statement_list = StatementList::new(
+                        false,
+                        true,
+                        false,
+                        &FUNCTION_BREAK_TOKENS,
+                        false,
+                        false,
+                    )
+                    .parse(cursor, interner)?;
 
                     let mut lexical_names = FxHashSet::default();
                     for name in &lexically_declared_names(&statement_list) {

boa_parser/src/parser/statement/mod.rs

@@ -50,6 +50,7 @@ use boa_ast::{
     Keyword, Punctuator,
 };
 use boa_interner::Interner;
+use boa_macros::utf16;
 use boa_profiler::Profiler;
 use std::io::Read;
 
@@ -228,6 +229,8 @@ pub(super) struct StatementList {
     allow_await: AllowAwait,
     allow_return: AllowReturn,
     break_nodes: &'static [TokenKind],
+    directive_prologues: bool,
+    strict: bool,
 }
 
 impl StatementList {
@@ -237,6 +240,8 @@ impl StatementList {
         allow_await: A,
         allow_return: R,
         break_nodes: &'static [TokenKind],
+        directive_prologues: bool,
+        strict: bool,
     ) -> Self
     where
         Y: Into<AllowYield>,
@@ -248,6 +253,8 @@ impl StatementList {
             allow_await: allow_await.into(),
             allow_return: allow_return.into(),
             break_nodes,
+            directive_prologues,
+            strict,
         }
     }
 }
@@ -272,6 +279,10 @@ where
         let _timer = Profiler::global().start_event("StatementList", "Parsing");
         let mut items = Vec::new();
 
+        let global_strict = cursor.strict_mode();
+        let mut directive_prologues = self.directive_prologues;
+        let mut strict = self.strict;
+
         loop {
             match cursor.peek(0, interner)? {
                 Some(token) if self.break_nodes.contains(token.kind()) => break,
@@ -282,6 +293,25 @@ where
             let item =
                 StatementListItem::new(self.allow_yield, self.allow_await, self.allow_return)
                     .parse(cursor, interner)?;
+
+            if directive_prologues {
+                if let ast::StatementListItem::Statement(ast::Statement::Expression(
+                    ast::Expression::Literal(ast::expression::literal::Literal::String(string)),
+                )) = &item
+                {
+                    if interner.resolve_expect(*string).join(
+                        |s| s == "use strict",
+                        |g| g == utf16!("use strict"),
+                        true,
+                    ) {
+                        cursor.set_strict_mode(true);
+                        strict = true;
+                    }
+                } else {
+                    directive_prologues = false;
+                }
+            }
+
             items.push(item);
 
             // move the cursor forward for any consecutive semicolon.
@@ -290,7 +320,9 @@ where
 
         items.sort_by(ast::StatementListItem::hoistable_order);
 
-        Ok(items.into())
+        cursor.set_strict_mode(global_strict);
+
+        Ok(ast::StatementList::new(items, strict))
     }
 }
 

boa_parser/src/parser/statement/switch/mod.rs

@@ -173,6 +173,8 @@ where
                         self.allow_await,
                         self.allow_return,
                         &CASE_BREAK_TOKENS,
+                        false,
+                        false,
                     )
                     .parse(cursor, interner)?;
 
@@ -195,6 +197,8 @@ where
                         self.allow_await,
                         self.allow_return,
                         &CASE_BREAK_TOKENS,
+                        false,
+                        false,
                     )
                     .parse(cursor, interner)?;