Refactor environment, exception handling and jumping in VM

boa_engine/src/builtins/eval/mod.rs

@@ -253,7 +253,10 @@ impl Eval {
             context.vm.environments.extend_outer_function_environment();
         }
 
-        context.vm.push_frame(CallFrame::new(code_block));
+        let env_fp = context.vm.environments.len() as u32;
+        context
+            .vm
+            .push_frame(CallFrame::new(code_block).with_env_fp(env_fp));
         context.realm().resize_global_env();
         let record = context.run();
         context.vm.pop_frame();

boa_engine/src/builtins/json/mod.rs

@@ -128,7 +128,10 @@ impl Json {
             Gc::new(compiler.finish())
         };
 
-        context.vm.push_frame(CallFrame::new(code_block));
+        let env_fp = context.vm.environments.len() as u32;
+        context
+            .vm
+            .push_frame(CallFrame::new(code_block).with_env_fp(env_fp));
         context.realm().resize_global_env();
         let record = context.run();
         context.vm.pop_frame();

boa_engine/src/bytecompiler/declaration/declaration_pattern.rs

@@ -180,11 +180,45 @@ impl ByteCompiler<'_, '_> {
                 self.emit_opcode(Opcode::ValueNotNullOrUndefined);
                 self.emit_opcode(Opcode::GetIterator);
 
+                // TODO: maybe, refactor this to be more condensed.
+                let handler_index = self.push_handler();
                 for element in pattern.bindings() {
                     self.compile_array_pattern_element(element, def);
                 }
+                let handler_end_address = self.next_opcode_location();
 
+                self.emit_opcode(Opcode::PushFalse);
+
+                let exit = self.jump();
+                let handler_address = self.next_opcode_location();
+                self.emit_opcode(Opcode::Exception);
+                self.emit_opcode(Opcode::PushTrue);
+                self.patch_jump(exit);
+
+                self.handlers[handler_index as usize].handler = handler_address;
+                self.handlers[handler_index as usize].range.end = handler_end_address;
+
+                let iterator_close_handler = self.push_handler();
                 self.iterator_close(false);
+
+                let exit = self.jump();
+                let iterator_close_handler_address = self.next_opcode_location();
+                {
+                    let jump = self.jump_if_false();
+                    self.emit_opcode(Opcode::Throw);
+                    self.patch_jump(jump);
+                }
+                self.emit_opcode(Opcode::ReThrow);
+                self.patch_jump(exit);
+
+                let jump = self.jump_if_false();
+                self.emit_opcode(Opcode::Throw);
+                self.patch_jump(jump);
+
+                self.handlers[iterator_close_handler as usize].handler =
+                    iterator_close_handler_address;
+                self.handlers[iterator_close_handler as usize].range.end =
+                    iterator_close_handler_address;
             }
         }
     }
@@ -198,15 +232,15 @@ impl ByteCompiler<'_, '_> {
         match element {
             // ArrayBindingPattern : [ Elision ]
             Elision => {
-                self.emit_opcode(Opcode::IteratorNext);
+                self.emit_opcode(Opcode::IteratorNextWithoutPop);
             }
             // SingleNameBinding : BindingIdentifier Initializer[opt]
             SingleName {
                 ident,
                 default_init,
             } => {
-                self.emit_opcode(Opcode::IteratorNext);
-                self.emit_opcode(Opcode::IteratorValue);
+                self.emit_opcode(Opcode::IteratorNextWithoutPop);
+                self.emit_opcode(Opcode::IteratorValueWithoutPop);
                 if let Some(init) = default_init {
                     let skip = self.emit_opcode_with_operand(Opcode::JumpIfNotUndefined);
                     self.compile_expr(init, true);
@@ -216,17 +250,17 @@ impl ByteCompiler<'_, '_> {
             }
             PropertyAccess { access } => {
                 self.access_set(Access::Property { access }, false, |compiler, _level| {
-                    compiler.emit_opcode(Opcode::IteratorNext);
-                    compiler.emit_opcode(Opcode::IteratorValue);
+                    compiler.emit_opcode(Opcode::IteratorNextWithoutPop);
+                    compiler.emit_opcode(Opcode::IteratorValueWithoutPop);
                 });
             }
             // BindingElement : BindingPattern Initializer[opt]
             Pattern {
                 pattern,
                 default_init,
             } => {
-                self.emit_opcode(Opcode::IteratorNext);
-                self.emit_opcode(Opcode::IteratorValue);
+                self.emit_opcode(Opcode::IteratorNextWithoutPop);
+                self.emit_opcode(Opcode::IteratorValueWithoutPop);
 
                 if let Some(init) = default_init {
                     let skip = self.emit_opcode_with_operand(Opcode::JumpIfNotUndefined);

boa_engine/src/bytecompiler/env.rs

@@ -7,6 +7,7 @@ use boa_ast::expression::Identifier;
 impl ByteCompiler<'_, '_> {
     /// Push either a new declarative or function environment on the compile time environment stack.
     pub(crate) fn push_compile_environment(&mut self, function_scope: bool) {
+        self.current_open_environments_count += 1;
         self.current_environment = Rc::new(CompileTimeEnvironment::new(
             self.current_environment.clone(),
             function_scope,
@@ -16,6 +17,7 @@ impl ByteCompiler<'_, '_> {
     /// Pops the top compile time environment and returns its index in the compile time environments array.
     #[track_caller]
     pub(crate) fn pop_compile_environment(&mut self) -> u32 {
+        self.current_open_environments_count -= 1;
         let index = self.compile_environments.len() as u32;
         self.compile_environments
             .push(self.current_environment.clone());