[ConstraintSystem] Increase impact of implicit Double<->CGFloat associated with contextual type

Consider conversion with context to be worse by default
because it means that expression as a whole couldn't get
to the expected type.

This also helps to disambiguate situations with
multiple solutions where one of them has a contextual
mismatch that requires implicit conversion and
another produces correct contextual type but requires
implicit conversion inside to get there.

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -10545,6 +10545,14 @@ ConstraintSystem::simplifyRestrictedConstraintImpl(
     auto defaultImpact =
         restriction == ConversionRestrictionKind::CGFloatToDouble ? 1 : 2;
 
+    // Consider conversion with context to be worse
+    // by default because it means that expression
+    // as a whole couldn't get to the expected type.
+    if (auto last = locator.last()) {
+      if (last->is<LocatorPathElt::ContextualType>())
+        ++defaultImpact;
+    }
+
     auto numConversions = ImplicitValueConversions.size();
     increaseScore(SK_ImplicitValueConversion,
                   defaultImpact * (numConversions + 1));