[ConstraintSystem] Adjust Double<->CGFloat locator when used as dictionary key/value

Original locator carries information about key and value types which
is necessary for diagnostics but cannot be retrieved in its original
state during solution application, so it could be dropped from Double<->CGFloat
constructor locator.

Author: xedin

lib/Sema/ConstraintSystem.cpp

@@ -429,6 +429,11 @@ ConstraintLocator *ConstraintSystem::getImplicitValueConversionLocator(
   SmallVector<LocatorPathElt, 4> path;
   auto anchor = root.getLocatorParts(path);
   {
+    if (isExpr<DictionaryExpr>(anchor) && path.size() > 1) {
+      // Drop everything except to first `tuple element #`.
+      path.pop_back_n(path.size() - 1);
+    }
+
     // Drop any value-to-optional conversions that were applied along the
     // way to reach this one.
     while (!path.empty()) {