[CS] Correctly set key path component types

Previously we missed caching component types in
one case, and cached the wrong type in another.
Make both cases use cacheExprTypes to cache the
correct component types.

Author: hamishknight

lib/Sema/CSApply.cpp

@@ -1550,6 +1550,7 @@ namespace {
                                        ctx.Id_dynamicMember, componentLoc,
                                        components);
         keyPath->resolveComponents(ctx, components);
+        cs.cacheExprTypes(keyPath);
         return keyPath;
       }
 
@@ -1640,10 +1641,9 @@ namespace {
       componentExpr->setType(ty);
       cs.cacheType(componentExpr);
 
-      cs.setType(keyPath, 0, ty);
-
       keyPath->setParsedPath(componentExpr);
       keyPath->resolveComponents(ctx, components);
+      cs.cacheExprTypes(keyPath);
       return keyPath;
     }