fix(es/resolver): Correctly check strict mode (#8851)

**Related issue:**

 - Closes #8842

crates/swc_ecma_minifier/tests/terser/compress/dead_code/dead_code_2_should_warn_strict/output.js

@@ -1,6 +1,6 @@
 "use strict";
 function f() {
-    var x, g;
+    var x, g1;
     g();
     x = 10;
     throw Error("foo");

crates/swc_ecma_minifier/tests/terser/compress/dead_code/dead_code_2_should_warn_strict/output.mangleOnly.js

@@ -1,6 +1,6 @@
 "use strict";
 function n() {
-    o();
+    g();
     n = 10;
     throw new Error("foo");
     if (n) {

crates/swc_ecma_transforms_base/src/resolver/mod.rs

@@ -558,11 +558,14 @@ impl<'a> VisitMut for Resolver<'a> {
                     child.mark_block(&mut s.span);
 
                     let old_strict_mode = child.strict_mode;
-                    child.strict_mode = s
-                        .stmts
-                        .first()
-                        .map(|stmt| stmt.is_use_strict())
-                        .unwrap_or(false);
+
+                    if !child.strict_mode {
+                        child.strict_mode = s
+                            .stmts
+                            .first()
+                            .map(|stmt| stmt.is_use_strict())
+                            .unwrap_or(false);
+                    }
                     // Prevent creating new scope.
                     s.stmts.visit_mut_with(child);
                     child.strict_mode = old_strict_mode;
@@ -901,11 +904,13 @@ impl<'a> VisitMut for Resolver<'a> {
             Some(body) => {
                 self.mark_block(&mut body.span);
                 let old_strict_mode = self.strict_mode;
-                self.strict_mode = body
-                    .stmts
-                    .first()
-                    .map(|stmt| stmt.is_use_strict())
-                    .unwrap_or(false);
+                if !self.strict_mode {
+                    self.strict_mode = body
+                        .stmts
+                        .first()
+                        .map(|stmt| stmt.is_use_strict())
+                        .unwrap_or(false);
+                }
                 // Prevent creating new scope.
                 body.visit_mut_children_with(self);
                 self.strict_mode = old_strict_mode;

crates/swc_ecma_transforms_base/tests/fixture.rs

@@ -10,7 +10,7 @@ use swc_ecma_visit::{
 };
 use testing::{fixture, run_test2, NormalizedOutput};
 
-pub fn print(cm: Lrc<SourceMap>, module: &Module) -> String {
+pub fn print(cm: Lrc<SourceMap>, program: &Program) -> String {
     let mut buf = vec![];
     {
         let mut emitter = Emitter {
@@ -23,7 +23,7 @@ pub fn print(cm: Lrc<SourceMap>, module: &Module) -> String {
         };
 
         // println!("Emitting: {:?}", module);
-        emitter.emit_module(module).unwrap();
+        emitter.emit_program(program).unwrap();
     }
 
     let s = String::from_utf8_lossy(&buf);
@@ -47,15 +47,15 @@ where
         let lexer = Lexer::new(syntax, EsVersion::latest(), StringInput::from(&*fm), None);
         let mut parser = Parser::new_from(lexer);
 
-        let module = parser
-            .parse_module()
+        let program = parser
+            .parse_program()
             .map_err(|err| err.into_diagnostic(&handler).emit())?;
 
         let mut folder = op();
 
-        let module = module.fold_with(&mut folder);
+        let program = program.fold_with(&mut folder);
 
-        let actual = print(cm, &module);
+        let actual = print(cm, &program);
         let actual = NormalizedOutput::from(actual);
 
         actual.compare_to_file(&output).unwrap();

crates/swc_ecma_transforms_base/tests/resolver/function/block/input.js

@@ -0,0 +1,12 @@
+export function k() {
+    function x() {
+        console.log("hi");
+    }
+    {
+        function x() {
+            console.log("merong");
+        }
+    }
+    return x;
+}
+k();

crates/swc_ecma_transforms_base/tests/resolver/function/block/output.js

@@ -0,0 +1,12 @@
+export function k__2() {
+    function x__3() {
+        console.log("hi");
+    }
+    {
+        function x__5() {
+            console.log("merong");
+        }
+    }
+    return x__3;
+}
+k__2();

crates/swc_ecma_transforms_base/tests/resolver/issues/6310/output.js

@@ -1,4 +1,4 @@
 switch(0){
-    case x__3:
-        function x__3() {}
+    case x__2:
+        function x__2() {}
 }

crates/swc_ecma_transforms_base/tests/resolver/issues/7685/output.js

@@ -2,4 +2,4 @@ var NaN__2 = 1;
 {
     let NaN__3 = 1;
     console.log(NaN__3);
-}console.log(NaN__2);
+}console.log(NaN);

crates/swc_ecma_transforms_base/tests/resolver/minifier/10/output.js

@@ -1,2 +1,2 @@
 var NaN__2;
-console.log(NaN__2.toString());
+console.log(NaN.toString());

crates/swc_ecma_transforms_base/tests/resolver/minifier/11/output.js

@@ -1,2 +1,2 @@
 var NaN__2 = 5;
-console.log(NaN__2.toString());
+console.log(NaN.toString());