Fixed assign operator precedence (#311)

Co-authored-by: Iban Eguia <razican@protonmail.ch>

boa/src/exec/tests.rs

@@ -60,7 +60,7 @@ fn spread_with_arguments() {
             function foo(...a) {
                 return arguments;
             }
-            
+
             var result = foo(...a);
         "#;
     forward(&mut engine, scenario);
@@ -248,6 +248,16 @@ fn test_short_circuit_evaluation() {
     assert_eq!(exec(short_circuit_eval), String::from("1"));
 }
 
+#[test]
+fn assign_operator_precedence() {
+    let src = r#"
+        let a = 1;
+        a = a + 1;
+        a
+    "#;
+    assert_eq!(exec(src), String::from("2"));
+}
+
 #[test]
 fn test_do_while_loop() {
     let simple_one = r#"

boa/src/syntax/parser/mod.rs

@@ -128,14 +128,6 @@ macro_rules! expression { ( $name:ident, $lower:ident, [ $( $op:path ),* ] ) =>
         let mut lhs = self. $lower ()?;
         while let Some(tok) = self.peek_skip_lineterminator() {
             match tok.kind {
-                // Parse assign expression
-                TokenKind::Punctuator(ref op) if op == &Punctuator::Assign => {
-                    let _ = self.next_skip_lineterminator().expect("token disappeared");
-                    lhs = Node::Assign(
-                        Box::new(lhs),
-                        Box::new(self. $lower ()?)
-                    )
-                }
                 TokenKind::Punctuator(ref op) if $( op == &$op )||* => {
                     let _ = self.next_skip_lineterminator().expect("token disappeared");
                     lhs = Node::BinOp(

boa/src/syntax/parser/tests.rs

@@ -710,6 +710,7 @@ fn check_function_declarations() {
     );
 }
 
+// Should be parsed as `new Class().method()` instead of `new (Class().method())`
 #[test]
 fn check_do_while() {
     check_parser(
@@ -742,5 +743,20 @@ fn check_construct_call_precedence() {
             )),
             vec![],
         )],
-    )
+    );
+}
+
+#[test]
+fn assing_operator_precedence() {
+    check_parser(
+        "a = a + 1",
+        &[Node::Assign(
+            Box::new(Node::Local(String::from("a"))),
+            Box::new(create_bin_op(
+                BinOp::Num(NumOp::Add),
+                Node::Local(String::from("a")),
+                Node::Const(Const::Num(1.0)),
+            )),
+        )],
+    );
 }