LibJS: Fix broken parsing of `!o.a`

Unary expressions parsing now respects precedence and associativity of
operators. This patch also makes `typeof` left-associative which was
an oversight.

Thanks to Conrad for helping me work this out. :^)

2 files changed, 26 insertions, 5 deletions

diff --git a/Libraries/LibJS/Parser.cpp b/Libraries/LibJS/Parser.cpp
index ef0791622b..c4f2a3966f 100644
--- a/Libraries/LibJS/Parser.cpp
+++ b/Libraries/LibJS/Parser.cpp
@@ -150,6 +150,7 @@ Associativity Parser::operator_associativity(TokenType type) const
     case TokenType::ExclamationMarkEquals:
     case TokenType::EqualsEqualsEquals:
     case TokenType::ExclamationMarkEqualsEquals:
+    case TokenType::Typeof:
     case TokenType::Ampersand:
     case TokenType::Caret:
     case TokenType::Pipe:
@@ -256,22 +257,24 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
 
 NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
 {
+    auto precedence = operator_precedence(m_current_token.type());
+    auto associativity = operator_associativity(m_current_token.type());
     switch (m_current_token.type()) {
     case TokenType::PlusPlus:
         consume();
-        return create_ast_node<UpdateExpression>(UpdateOp::Increment, parse_primary_expression(), true);
+        return create_ast_node<UpdateExpression>(UpdateOp::Increment, parse_expression(precedence, associativity), true);
     case TokenType::MinusMinus:
         consume();
-        return create_ast_node<UpdateExpression>(UpdateOp::Decrement, parse_primary_expression(), true);
+        return create_ast_node<UpdateExpression>(UpdateOp::Decrement, parse_expression(precedence, associativity), true);
     case TokenType::ExclamationMark:
         consume();
-        return create_ast_node<UnaryExpression>(UnaryOp::Not, parse_primary_expression());
+        return create_ast_node<UnaryExpression>(UnaryOp::Not, parse_expression(precedence, associativity));
     case TokenType::Tilde:
         consume();
-        return create_ast_node<UnaryExpression>(UnaryOp::BitwiseNot, parse_primary_expression());
+        return create_ast_node<UnaryExpression>(UnaryOp::BitwiseNot, parse_expression(precedence, associativity));
     case TokenType::Typeof:
         consume();
-        return create_ast_node<UnaryExpression>(UnaryOp::Typeof, parse_primary_expression());
+        return create_ast_node<UnaryExpression>(UnaryOp::Typeof, parse_expression(precedence, associativity));
     default:
         m_has_errors = true;
         expected("primary expression (missing switch case)");
diff --git a/Libraries/LibJS/Tests/parser-unary-associativity.js b/Libraries/LibJS/Tests/parser-unary-associativity.js
new file mode 100644
index 0000000000..240b20f61c
--- /dev/null
+++ b/Libraries/LibJS/Tests/parser-unary-associativity.js
@@ -0,0 +1,18 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var o = {};
+    o.a = 1;
+
+    assert(o.a === 1);
+    assert(!o.a === false);
+    assert(!o.a === !(o.a));
+    assert(~o.a === ~(o.a));
+
+    assert((typeof "x" === "string") === true);
+    assert(!(typeof "x" === "string") === false);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}