[ClangImporter] Don’t import Array/Dictionary as such in Hashable contexts yet

Array and Dictionary are now conditionally Hashable, so the importer wants to use them when importing NSArray and NSDictionary types in hashable contexts. Unfortunately, this currently means that a type like

    NSSet<NSDictionary<NSString *, id> *> *

gets imported as

    Set<Dictionary<String, Any>>,

which is invalid — Dictionary.Value needs to be Hashable, too:

    Set<Dictionary<String, AnyHashable>>

For now, work around this by explicitly turning NSArray and NSDictionary into AnyHashable when they are used as the first type parameter of NSSet or NSDictionary, ignoring Hashable conformance in this case. This reverts to the previous behavior.

Author: lorentey

lib/ClangImporter/ImportType.cpp

@@ -998,7 +998,14 @@ namespace {
             if (unboundDecl == Impl.SwiftContext.getDictionaryDecl() ||
                 unboundDecl == Impl.SwiftContext.getSetDecl()) {
               auto &keyType = importedTypeArgs[0];
-              if (!Impl.matchesHashableBound(keyType)) {
+              if (!Impl.matchesHashableBound(keyType) ||
+                  // Dictionary and Array conditionally conform to Hashable,
+                  // but the conformance doesn't necessarily apply with the
+                  // imported versions of their type arguments.
+                  // FIXME: Import their non-Hashable type parameters as
+                  // AnyHashable in this context.
+                  keyType->getStructOrBoundGenericStruct() == Impl.SwiftContext.getDictionaryDecl() ||
+                  keyType->getStructOrBoundGenericStruct() == Impl.SwiftContext.getArrayDecl()) {
                 if (auto anyHashable = Impl.SwiftContext.getAnyHashableDecl())
                   keyType = anyHashable->getDeclaredType();
                 else