node: elide some extra parentheses for commutative binary ops (plus/concat)

node.go

@@ -1490,6 +1490,17 @@ func (this *conversionState) convertBinaryCommon(left, right node.Node, goBinary
 		rhs = "(" + rhs + ")"
 	}
 
+	// We can elide even more parens in case of some commutative operators
+	// We can only do this in the left-associative case
+	// FIXME Plus and Concat aren't necessarily commutative together even though they both have + here(!!)
+	if _, ok := left.(*binary.Plus); ok && goBinaryOperator == `+` {
+		lhs = removeParens(lhs)
+	}
+	if _, ok := left.(*binary.Concat); ok && goBinaryOperator == `+` {
+		lhs = removeParens(lhs)
+	}
+
+	// Done
 	return "(" + lhs + " " + goBinaryOperator + " " + rhs + ")", nil
 }