[CSOptimizer] Allow literal inference inside of operator chains

This is helpful in situations when all of the chained operators
have literal arguments because it would make sure that every
operator has the same score if there is no contextual type.

Author: xedin

lib/Sema/CSOptimizer.cpp

@@ -450,7 +450,7 @@ inferTypeFromInitializerResultType(ConstraintSystem &cs,
   return {instanceTy, /*hasFailable=*/false};
 }
 
-/// If the given expression represents a chain of operators that only have
+/// If the given expression represents a chain of operators that have
 /// only literals as arguments, attempt to deduce a potential type of the
 /// chain. For example if chain has only integral literals it's going to
 /// be `Int`, if there are some floating-point literals mixed in - it's going
@@ -1007,13 +1007,9 @@ static void determineBestChoicesInContext(
         if (typeVar->getImpl().isFunctionResult()) {
           auto *resultLoc = typeVar->getImpl().getLocator();
 
-          // We don't want to try and infer parts of operator
-          // chains.
-          if (!isOperator) {
-            if (auto type = inferTypeOfArithmeticOperatorChain(
-                    cs.DC, resultLoc->getAnchor())) {
-              types.push_back({type, /*fromLiteral=*/true});
-            }
+          if (auto type = inferTypeOfArithmeticOperatorChain(
+                  cs.DC, resultLoc->getAnchor())) {
+            types.push_back({type, /*fromLiteral=*/true});
           }
 
           auto binding =