Check file type better in this verifier.

Ask the decl directly whether its source file is a sil source file.

Author: nate-chandler

lib/SIL/IR/TypeLowering.cpp

@@ -3228,19 +3228,17 @@ void TypeConverter::verifyTrivialLowering(const TypeLowering &lowering,
 
   if (auto *nominal = substType.getAnyNominal()) {
     auto *module = nominal->getModuleContext();
-    if (module) {
-      if (module->isBuiltFromInterface()) {
+    if (module && module->isBuiltFromInterface()) {
         // Don't verify for types in modules built from interfaces; the feature
         // may not have been enabled in them.
         return;
-      }
-      auto *file = dyn_cast_or_null<FileUnit>(module->getModuleScopeContext());
-      if (file && file->getKind() == FileUnitKind::Source) {
-        auto sourceFile = nominal->getParentSourceFile();
-        if (sourceFile && sourceFile->Kind == SourceFileKind::SIL) {
-          // Don't verify for types in SIL files.
-          return;
-        }
+    }
+    auto *file = nominal->getParentSourceFile();
+    if (file && file->getKind() == FileUnitKind::Source) {
+      auto sourceFile = nominal->getParentSourceFile();
+      if (sourceFile && sourceFile->Kind == SourceFileKind::SIL) {
+        // Don't verify for types in SIL files.
+        return;
       }
     }
   }

test/IRGen/enum_value_semantics_future.sil

@@ -8,6 +8,7 @@
 // UNSUPPORTED: CPU=armv7s && OS=ios
 
 import Builtin
+import Swift
 
 enum NoPayload {
   case a