LibJS: Implement exponentiation assignment operator (**=)

Libraries/LibGUI/JSSyntaxHighlighter.cpp

@@ -62,7 +62,7 @@ static TextStyle style_for_token_type(Gfx::Palette palette, JS::TokenType type)
     case JS::TokenType::Ampersand:
     case JS::TokenType::AmpersandEquals:
     case JS::TokenType::Asterisk:
-    case JS::TokenType::AsteriskAsteriskEquals:
+    case JS::TokenType::DoubleAsteriskEquals:
     case JS::TokenType::AsteriskEquals:
     case JS::TokenType::Caret:
     case JS::TokenType::CaretEquals:

Libraries/LibJS/AST.cpp

@@ -850,6 +850,12 @@ Value AssignmentExpression::execute(Interpreter& interpreter) const
             return {};
         rhs_result = div(interpreter, lhs_result, rhs_result);
         break;
+    case AssignmentOp::ExponentiationAssignment:
+        lhs_result = m_lhs->execute(interpreter);
+        if (interpreter.exception())
+            return {};
+        rhs_result = exp(interpreter, lhs_result, rhs_result);
+        break;
     case AssignmentOp::BitwiseAndAssignment:
         lhs_result = m_lhs->execute(interpreter);
         if (interpreter.exception())
@@ -954,6 +960,9 @@ void AssignmentExpression::dump(int indent) const
     case AssignmentOp::DivisionAssignment:
         op_string = "/=";
         break;
+    case AssignmentOp::ExponentiationAssignment:
+        op_string = "**=";
+        break;
     case AssignmentOp::BitwiseAndAssignment:
         op_string = "&=";
         break;

Libraries/LibJS/AST.h

@@ -604,6 +604,7 @@ enum class AssignmentOp {
     SubtractionAssignment,
     MultiplicationAssignment,
     DivisionAssignment,
+    ExponentiationAssignment,
     BitwiseAndAssignment,
     BitwiseOrAssignment,
     BitwiseXorAssignment,

Libraries/LibJS/Lexer.cpp

@@ -81,7 +81,7 @@ Lexer::Lexer(StringView source)
     if (s_three_char_tokens.is_empty()) {
         s_three_char_tokens.set("===", TokenType::EqualsEqualsEquals);
         s_three_char_tokens.set("!==", TokenType::ExclamationMarkEqualsEquals);
-        s_three_char_tokens.set("**=", TokenType::AsteriskAsteriskEquals);
+        s_three_char_tokens.set("**=", TokenType::DoubleAsteriskEquals);
         s_three_char_tokens.set("<<=", TokenType::ShiftLeftEquals);
         s_three_char_tokens.set(">>=", TokenType::ShiftRightEquals);
         s_three_char_tokens.set(">>>", TokenType::UnsignedShiftRight);

Libraries/LibJS/Parser.cpp

@@ -133,7 +133,7 @@ Parser::Parser(Lexer lexer)
         g_operator_precedence.set(TokenType::Equals, 3);
         g_operator_precedence.set(TokenType::PlusEquals, 3);
         g_operator_precedence.set(TokenType::MinusEquals, 3);
-        g_operator_precedence.set(TokenType::AsteriskAsteriskEquals, 3);
+        g_operator_precedence.set(TokenType::DoubleAsteriskEquals, 3);
         g_operator_precedence.set(TokenType::AsteriskEquals, 3);
         g_operator_precedence.set(TokenType::SlashEquals, 3);
         g_operator_precedence.set(TokenType::PercentEquals, 3);
@@ -637,6 +637,9 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(NonnullRefPtr<Expre
     case TokenType::DoubleAsterisk:
         consume();
         return create_ast_node<BinaryExpression>(BinaryOp::Exponentiation, move(lhs), parse_expression(min_precedence, associativity));
+    case TokenType::DoubleAsteriskEquals:
+        consume();
+        return create_ast_node<AssignmentExpression>(AssignmentOp::ExponentiationAssignment, move(lhs), parse_expression(min_precedence, associativity));
     case TokenType::GreaterThan:
         consume();
         return create_ast_node<BinaryExpression>(BinaryOp::GreaterThan, move(lhs), parse_expression(min_precedence, associativity));
@@ -1192,6 +1195,7 @@ bool Parser::match_secondary_expression() const
         || type == TokenType::SlashEquals
         || type == TokenType::Percent
         || type == TokenType::DoubleAsterisk
+        || type == TokenType::DoubleAsteriskEquals
         || type == TokenType::Equals
         || type == TokenType::EqualsEqualsEquals
         || type == TokenType::ExclamationMarkEqualsEquals

Libraries/LibJS/Tests/assignment-operators.js

@@ -23,6 +23,10 @@ try {
     assert((x /= 2) === 3);
     assert(x === 3);
 
+    x = 2;
+    assert((x **= 3) === 8);
+    assert(x === 8);
+
     x = 3;
     assert((x &= 2) === 2);
     assert(x === 2);

Libraries/LibJS/Token.h

@@ -36,7 +36,7 @@ namespace JS {
     __ENUMERATE_JS_TOKEN(AmpersandEquals)             \
     __ENUMERATE_JS_TOKEN(Arrow)                       \
     __ENUMERATE_JS_TOKEN(Asterisk)                    \
-    __ENUMERATE_JS_TOKEN(AsteriskAsteriskEquals)      \
+    __ENUMERATE_JS_TOKEN(DoubleAsteriskEquals)        \
     __ENUMERATE_JS_TOKEN(AsteriskEquals)              \
     __ENUMERATE_JS_TOKEN(Await)                       \
     __ENUMERATE_JS_TOKEN(BoolLiteral)                 \

Userland/js.cpp

@@ -567,7 +567,7 @@ int main(int argc, char** argv)
                 case JS::TokenType::Ampersand:
                 case JS::TokenType::AmpersandEquals:
                 case JS::TokenType::Asterisk:
-                case JS::TokenType::AsteriskAsteriskEquals:
+                case JS::TokenType::DoubleAsteriskEquals:
                 case JS::TokenType::AsteriskEquals:
                 case JS::TokenType::Caret:
                 case JS::TokenType::CaretEquals: