Implement logical assignment operators (&&= and ||=) (#1018)

* Implement logical assignment operators (&&= and ||=)

* Add unit tests

Co-authored-by: tofpie <tofpie@users.noreply.github.com>

boa/src/syntax/ast/node/operator/bin_op/mod.rs

@@ -71,6 +71,20 @@ impl BinOp {
             AssignOp::Shl => x.shl(&y.run(context)?, context),
             AssignOp::Shr => x.shr(&y.run(context)?, context),
             AssignOp::Ushr => x.ushr(&y.run(context)?, context),
+            AssignOp::BoolAnd => {
+                if x.to_boolean() {
+                    Ok(y.run(context)?)
+                } else {
+                    Ok(x)
+                }
+            }
+            AssignOp::BoolOr => {
+                if x.to_boolean() {
+                    Ok(x)
+                } else {
+                    Ok(y.run(context)?)
+                }
+            }
             AssignOp::Coalesce => {
                 if x.is_null_or_undefined() {
                     Ok(y.run(context)?)

boa/src/syntax/ast/node/operator/tests.rs

@@ -79,3 +79,37 @@ fn logical_nullish_assignment() {
 
     assert_eq!(&exec(scenario), "20");
 }
+
+#[test]
+fn logical_assignment() {
+    let scenario = r#"
+        let a = false;
+        a &&= 10;
+        a;
+        "#;
+
+    assert_eq!(&exec(scenario), "false");
+
+    let scenario = r#"
+        let a = 20;
+        a &&= 10;
+        a;
+        "#;
+
+    assert_eq!(&exec(scenario), "10");
+
+    let scenario = r#"
+        let a = null;
+        a ||= 10;
+        a;
+        "#;
+
+    assert_eq!(&exec(scenario), "10");
+    let scenario = r#"
+        let a = 20;
+        a ||= 10;
+        a;
+        "#;
+
+    assert_eq!(&exec(scenario), "20");
+}

boa/src/syntax/ast/op.rs

@@ -965,6 +965,30 @@ pub enum AssignOp {
     /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift_assignment
     Ushr,
 
+    /// The logical and assignment operator only assigns if the target variable is truthy.
+    ///
+    /// Syntax: `x &&= y`
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#prod-AssignmentExpression
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_AND_assignment
+    BoolAnd,
+
+    /// The logical or assignment operator only assigns if the target variable is falsy.
+    ///
+    /// Syntax: `x ||= y`
+    ///
+    /// More information:
+    ///  - [ECMAScript reference][spec]
+    ///  - [MDN documentation][mdn]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#prod-AssignmentExpression
+    /// [mdn]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_OR_assignment
+    BoolOr,
+
     /// The logical nullish assignment operator only assigns if the target variable is nullish (null or undefined).
     ///
     /// Syntax: `x ??= y`
@@ -1000,6 +1024,8 @@ impl Display for AssignOp {
                 Self::Shl => "<<=",
                 Self::Shr => ">>=",
                 Self::Ushr => ">>>=",
+                Self::BoolAnd => "&&=",
+                Self::BoolOr => "||=",
                 Self::Coalesce => "??=",
             }
         )

boa/src/syntax/ast/punctuator.rs

@@ -35,6 +35,10 @@ pub enum Punctuator {
     AssignAdd,
     /// `&=`
     AssignAnd,
+    /// `&&=`
+    AssignBoolAnd,
+    /// `||=`
+    AssignBoolOr,
     /// `??=`,
     AssignCoalesce,
     /// `/=`
@@ -141,6 +145,8 @@ impl Punctuator {
         match self {
             Self::AssignAdd => Some(BinOp::Assign(AssignOp::Add)),
             Self::AssignAnd => Some(BinOp::Assign(AssignOp::And)),
+            Self::AssignBoolAnd => Some(BinOp::Assign(AssignOp::BoolAnd)),
+            Self::AssignBoolOr => Some(BinOp::Assign(AssignOp::BoolOr)),
             Self::AssignCoalesce => Some(BinOp::Assign(AssignOp::Coalesce)),
             Self::AssignDiv => Some(BinOp::Assign(AssignOp::Div)),
             Self::AssignLeftSh => Some(BinOp::Assign(AssignOp::Shl)),
@@ -200,6 +206,8 @@ impl Display for Punctuator {
                 Self::Assign => "=",
                 Self::AssignAdd => "+=",
                 Self::AssignAnd => "&=",
+                Self::AssignBoolAnd => "&&=",
+                Self::AssignBoolOr => "||=",
                 Self::AssignCoalesce => "??=",
                 Self::AssignDiv => "/=",
                 Self::AssignLeftSh => "<<=",

boa/src/syntax/lexer/operator.rs

@@ -119,10 +119,10 @@ impl<R> Tokenizer<R> for Operator {
                 Ok(Punctuator::Mod)
             ),
             b'|' => op!(cursor, start_pos, Ok(Punctuator::AssignOr), Ok(Punctuator::Or), {
-                Some(b'|') => Ok(Punctuator::BoolOr)
+                Some(b'|') => vop!(cursor, Ok(Punctuator::AssignBoolOr), Ok(Punctuator::BoolOr))
             }),
             b'&' => op!(cursor, start_pos, Ok(Punctuator::AssignAnd), Ok(Punctuator::And), {
-                Some(b'&') => Ok(Punctuator::BoolAnd)
+                Some(b'&') => vop!(cursor, Ok(Punctuator::AssignBoolAnd), Ok(Punctuator::BoolAnd))
             }),
             b'?' => match cursor.peek()? {
                 Some(b'?') => {

boa/src/syntax/lexer/tests.rs

@@ -109,7 +109,7 @@ fn check_punctuators() {
     // https://tc39.es/ecma262/#sec-punctuators
     let s = "{ ( ) [ ] . ... ; , < > <= >= == != === !== \
              + - * % -- << >> >>> & | ^ ! ~ && || ? : \
-             = += -= *= &= **= ++ ** <<= >>= >>>= &= |= ^= => ?? ??=";
+             = += -= *= &= **= ++ ** <<= >>= >>>= &= |= ^= => ?? ??= &&= ||=";
     let mut lexer = Lexer::new(s.as_bytes());
 
     let expected = [
@@ -164,6 +164,8 @@ fn check_punctuators() {
         TokenKind::Punctuator(Punctuator::Arrow),
         TokenKind::Punctuator(Punctuator::Coalesce),
         TokenKind::Punctuator(Punctuator::AssignCoalesce),
+        TokenKind::Punctuator(Punctuator::AssignBoolAnd),
+        TokenKind::Punctuator(Punctuator::AssignBoolOr),
     ];
 
     expect_tokens(&mut lexer, &expected);