fix(es/parser): Fix detection of use strict directive (#8617)

**Description:**

Directives should be at the start of the file, and this PR changes the parser to match only at the start of a file.

**Related issue:**

 - Closes #8616.

Author: kdy1

crates/swc/tests/fixture/issues-8xxx/8616/input/1.js

@@ -0,0 +1,18 @@
+
+var Module = (() => {
+    var _scriptDir = typeof document !== 'undefined' && document.currentScript ? document.currentScript.src : undefined;
+    if (typeof __filename !== 'undefined') _scriptDir ||= __filename;
+    return (
+        function (moduleArg = {}) {
+            var Module = moduleArg;
+            var readyPromiseResolve, readyPromiseReject; Module["ready"] = new Promise((resolve, reject) => { readyPromiseResolve = resolve; readyPromiseReject = reject }); "use strict";
+
+
+            return moduleArg
+        }
+    );
+})()();
+if (typeof exports === 'object' && typeof module === 'object')
+    module.exports = Module;
+else if (typeof define === 'function' && define['amd'])
+    define([], () => Module);

crates/swc/tests/fixture/issues-8xxx/8616/output/1.js

@@ -0,0 +1,19 @@
+var Module = (function() {
+    var _scriptDir = typeof document !== "undefined" && document.currentScript ? document.currentScript.src : undefined;
+    if (typeof __filename !== "undefined") _scriptDir || (_scriptDir = __filename);
+    return function() {
+        var moduleArg = arguments.length > 0 && arguments[0] !== void 0 ? arguments[0] : {};
+        var Module = moduleArg;
+        var readyPromiseResolve, readyPromiseReject;
+        Module["ready"] = new Promise(function(resolve, reject) {
+            readyPromiseResolve = resolve;
+            readyPromiseReject = reject;
+        });
+        "use strict";
+        return moduleArg;
+    };
+})()();
+if (typeof exports === "object" && typeof module === "object") module.exports = Module;
+else if (typeof define === "function" && define["amd"]) define([], function() {
+    return Module;
+});

crates/swc_ecma_ast/src/stmt.rs

@@ -6,7 +6,7 @@ use crate::{
     expr::Expr,
     ident::Ident,
     pat::Pat,
-    UsingDecl,
+    Lit, Str, UsingDecl,
 };
 
 /// Use when only block statements are allowed.
@@ -106,6 +106,29 @@ pub enum Stmt {
     Expr(ExprStmt),
 }
 
+impl Stmt {
+    pub fn is_use_strict(&self) -> bool {
+        match self {
+            Stmt::Expr(expr) => match *expr.expr {
+                Expr::Lit(Lit::Str(Str { ref raw, .. })) => {
+                    matches!(raw, Some(value) if value == "\"use strict\"" || value == "'use strict'")
+                }
+                _ => false,
+            },
+            _ => false,
+        }
+    }
+
+    /// Returns true if the statement does not prevent the directives below
+    /// `self` from being directives.
+    pub fn can_precede_directive(&self) -> bool {
+        match self {
+            Stmt::Expr(expr) => matches!(*expr.expr, Expr::Lit(Lit::Str(_))),
+            _ => false,
+        }
+    }
+}
+
 // Memory layout depedns on the version of rustc.
 // #[cfg(target_pointer_width = "64")]
 // assert_eq_size!(Stmt, [u8; 56]);

crates/swc_ecma_compat_es2015/src/classes/mod.rs

@@ -12,7 +12,7 @@ use swc_ecma_transforms_macros::fast_path;
 use swc_ecma_utils::{
     alias_if_required, contains_this_expr, default_constructor, is_valid_ident,
     is_valid_prop_ident, prepend_stmt, private_ident, prop_name_to_expr, quote_expr, quote_ident,
-    quote_str, replace_ident, ExprFactory, IdentExt, IsDirective, ModuleItemLike, StmtLike,
+    quote_str, replace_ident, ExprFactory, IdentExt, ModuleItemLike, StmtLike,
 };
 use swc_ecma_visit::{
     as_folder, noop_visit_mut_type, noop_visit_type, Fold, Visit, VisitMut, VisitMutWith, VisitWith,

crates/swc_ecma_parser/src/parser/class_and_fn.rs

@@ -1,7 +1,7 @@
 use swc_common::{Spanned, SyntaxContext};
 
 use super::*;
-use crate::{error::SyntaxError, lexer::TokenContext, parser::stmt::IsDirective, Tokens};
+use crate::{error::SyntaxError, lexer::TokenContext, Tokens};
 
 /// Parser for function expression and function declaration.
 impl<I: Tokens> Parser<I> {
@@ -1615,10 +1615,17 @@ pub(super) trait FnBodyParser<Body> {
     fn parse_fn_body_inner(&mut self, is_simple_parameter_list: bool) -> PResult<Body>;
 }
 fn has_use_strict(block: &BlockStmt) -> Option<Span> {
-    match block.stmts.iter().find(|stmt| stmt.is_use_strict()) {
-        Some(Stmt::Expr(ExprStmt { span, expr: _ })) => Some(*span),
-        _ => None,
-    }
+    block
+        .stmts
+        .iter()
+        .take_while(|s| s.can_precede_directive())
+        .find_map(|s| {
+            if s.is_use_strict() {
+                Some(s.span())
+            } else {
+                None
+            }
+        })
 }
 impl<I: Tokens> FnBodyParser<Box<BlockStmtOrExpr>> for Parser<I> {
     fn parse_fn_body_inner(

crates/swc_ecma_parser/src/parser/stmt.rs

@@ -1394,15 +1394,7 @@ enum TempForHead {
 pub(super) trait IsDirective {
     fn as_ref(&self) -> Option<&Stmt>;
     fn is_use_strict(&self) -> bool {
-        match self.as_ref() {
-            Some(Stmt::Expr(expr)) => match *expr.expr {
-                Expr::Lit(Lit::Str(Str { ref raw, .. })) => {
-                    matches!(raw, Some(value) if value == "\"use strict\"" || value == "'use strict'")
-                }
-                _ => false,
-            },
-            _ => false,
-        }
+        self.as_ref().map_or(false, Stmt::is_use_strict)
     }
 }
 

crates/swc_ecma_transforms_base/src/resolver/mod.rs

@@ -5,7 +5,7 @@ use swc_common::{
     Mark, Span, SyntaxContext,
 };
 use swc_ecma_ast::*;
-use swc_ecma_utils::{find_pat_ids, IsDirective};
+use swc_ecma_utils::find_pat_ids;
 use swc_ecma_visit::{
     as_folder, noop_visit_mut_type, visit_mut_obj_and_computed, Fold, VisitMut, VisitMutWith,
 };

crates/swc_ecma_utils/src/lib.rs

@@ -2306,24 +2306,10 @@ pub trait IsDirective {
         }
     }
     fn directive_continue(&self) -> bool {
-        match self.as_ref() {
-            Some(Stmt::Expr(expr)) => match &*expr.expr {
-                Expr::Lit(Lit::Str(..)) => true,
-                _ => false,
-            },
-            _ => false,
-        }
+        self.as_ref().map_or(false, Stmt::can_precede_directive)
     }
     fn is_use_strict(&self) -> bool {
-        match self.as_ref() {
-            Some(Stmt::Expr(expr)) => match *expr.expr {
-                Expr::Lit(Lit::Str(Str { ref raw, .. })) => {
-                    matches!(raw, Some(value) if value == "\"use strict\"" || value == "'use strict'")
-                }
-                _ => false,
-            },
-            _ => false,
-        }
+        self.as_ref().map_or(false, Stmt::is_use_strict)
     }
 }