[CSSimplify] Increase fix impact when passing closure to a non-function type parameter

In overloaded context it's possible that there is an overload that
expects a closure but it can have other issues e.g. different number
of parameters, so in order to pick a better solution let's always
increase a score for overloads where closure is matched against a
non-function type parameter.

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -11393,6 +11393,16 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
         }))
       impact += 3;
 
+    // Passing a closure to a parameter that doesn't expect one should
+    // be scored lower because there might be an overload that expects
+    // a closure but has other issues e.g. wrong number of parameters.
+    if (!type2->lookThroughAllOptionalTypes()->is<FunctionType>()) {
+      auto argument = simplifyLocatorToAnchor(fix->getLocator());
+      if (isExpr<ClosureExpr>(argument)) {
+        impact += 2;
+      }
+    }
+
     return recordFix(fix, impact) ? SolutionKind::Error : SolutionKind::Solved;
   }