Merge pull request #3799 from meowingtwurtle/fixLiteralComparisons

Fix bug in typechecking when comparing rational literals

Changelog.md

@@ -27,6 +27,7 @@ Bugfixes:
  * DocString Parser: Fix error message for empty descriptions.
  * Standard JSON: Support ``constantinople`` as ``evmVersion`` properly.
  * Type Checker: Fix detection of recursive structs.
+ * Type Checker: Fix asymmetry bug when comparing with literal numbers.
  * Type System: Improve error message when attempting to shift by a fractional amount.
  * Type System: Make external library functions accessible.
  * Type System: Prevent encoding of weird types.

libsolidity/ast/Types.cpp

@@ -839,10 +839,10 @@ TypePointer RationalNumberType::binaryOperatorResult(Token::Value _operator, Typ
 {
 	if (_other->category() == Category::Integer || _other->category() == Category::FixedPoint)
 	{
-		auto mobile = mobileType();
-		if (!mobile)
+		auto commonType = Type::commonType(shared_from_this(), _other);
+		if (!commonType)
 			return TypePointer();
-		return mobile->binaryOperatorResult(_operator, _other);
+		return commonType->binaryOperatorResult(_operator, _other);
 	}
 	else if (_other->category() != category())
 		return TypePointer();

test/libsolidity/syntaxTests/literal_comparisons.sol

@@ -0,0 +1,7 @@
+contract test {
+    function f(int8 x) public pure {
+        if (x == 1) {}
+        if (1 == x) {}
+    }
+}
+// ----