Fix `this` in function calls (#2153)

This Pull Request changes the following:

- Fix the `this` value that is passend to function calls to be `undefined` if the function is not a property reference
- Add special handling for setting the `this` value for function calls where the function is a private property reference or a super property reference

boa_engine/src/bytecompiler.rs

@@ -2162,10 +2162,35 @@ impl<'b> ByteCompiler<'b> {
                 self.emit(Opcode::Swap, &[]);
                 self.emit(Opcode::GetPropertyByValue, &[]);
             }
+            Node::GetSuperField(get_super_field) => {
+                if kind == CallKind::Call {
+                    self.emit_opcode(Opcode::This);
+                }
+                self.emit_opcode(Opcode::Super);
+                match get_super_field {
+                    GetSuperField::Const(field) => {
+                        let index = self.get_or_insert_name(*field);
+                        self.emit(Opcode::GetPropertyByName, &[index]);
+                    }
+                    GetSuperField::Expr(expr) => {
+                        self.compile_expr(expr, true)?;
+                        self.emit_opcode(Opcode::Swap);
+                        self.emit_opcode(Opcode::GetPropertyByValue);
+                    }
+                }
+            }
+            Node::GetPrivateField(get_private_field) => {
+                self.compile_expr(get_private_field.obj(), true)?;
+                if kind == CallKind::Call {
+                    self.emit(Opcode::Dup, &[]);
+                }
+                let index = self.get_or_insert_name(get_private_field.field());
+                self.emit(Opcode::GetPrivateField, &[index]);
+            }
             expr => {
                 self.compile_expr(expr, true)?;
                 if kind == CallKind::Call || kind == CallKind::CallEval {
-                    self.emit_opcode(Opcode::This);
+                    self.emit_opcode(Opcode::PushUndefined);
                     self.emit_opcode(Opcode::Swap);
                 }
             }

boa_engine/src/vm/mod.rs

@@ -1707,17 +1707,13 @@ impl Context {
                 arguments.reverse();
 
                 let func = self.vm.pop();
-                let mut this = self.vm.pop();
+                let this = self.vm.pop();
 
                 let object = match func {
                     JsValue::Object(ref object) if object.is_callable() => object.clone(),
                     _ => return self.throw_type_error("not a callable function"),
                 };
 
-                if this.is_null_or_undefined() {
-                    this = self.global_object().clone().into();
-                }
-
                 // A native function with the name "eval" implies, that is this the built-in eval function.
                 let eval = matches!(object.borrow().as_function(), Some(Function::Native { .. }));
 
@@ -1748,7 +1744,7 @@ impl Context {
                 }
                 arguments.reverse();
                 let func = self.vm.pop();
-                let mut this = self.vm.pop();
+                let this = self.vm.pop();
 
                 let iterator_record = rest_argument.get_iterator(self, None, None)?;
                 let mut rest_arguments = Vec::new();
@@ -1762,10 +1758,6 @@ impl Context {
                     _ => return self.throw_type_error("not a callable function"),
                 };
 
-                if this.is_null_or_undefined() {
-                    this = self.global_object().clone().into();
-                }
-
                 // A native function with the name "eval" implies, that is this the built-in eval function.
                 let eval = matches!(object.borrow().as_function(), Some(Function::Native { .. }));
 
@@ -1796,17 +1788,13 @@ impl Context {
                 arguments.reverse();
 
                 let func = self.vm.pop();
-                let mut this = self.vm.pop();
+                let this = self.vm.pop();
 
                 let object = match func {
                     JsValue::Object(ref object) if object.is_callable() => object.clone(),
                     _ => return self.throw_type_error("not a callable function"),
                 };
 
-                if this.is_null_or_undefined() {
-                    this = self.global_object().clone().into();
-                }
-
                 let result = object.__call__(&this, &arguments, self)?;
 
                 self.vm.push(result);
@@ -1823,7 +1811,7 @@ impl Context {
                 }
                 arguments.reverse();
                 let func = self.vm.pop();
-                let mut this = self.vm.pop();
+                let this = self.vm.pop();
 
                 let iterator_record = rest_argument.get_iterator(self, None, None)?;
                 let mut rest_arguments = Vec::new();
@@ -1837,10 +1825,6 @@ impl Context {
                     _ => return self.throw_type_error("not a callable function"),
                 };
 
-                if this.is_null_or_undefined() {
-                    this = self.global_object().clone().into();
-                }
-
                 let result = object.__call__(&this, &arguments, self)?;
 
                 self.vm.push(result);