Merge pull request #72163 from DougGregor/noncopyable-field-reflection-heuristic

Author: DougGregor

lib/IRGen/GenReflection.cpp

@@ -411,10 +411,28 @@ getTypeRefImpl(IRGenModule &IGM,
     // signal from future runtimes whether they support noncopyable types before
     // exposing their metadata to them.
     Type contextualTy = type;
-    if (sig)
+    if (sig) {
       contextualTy = sig.getGenericEnvironment()->mapTypeIntoContext(type);
+    }
 
+    bool isAlwaysNoncopyable = false;
     if (contextualTy->isNoncopyable()) {
+      // If the contextual type has any archetypes in it, it's plausible that
+      // we could end up with a copyable type in some instances. Look for those.
+      if (contextualTy->hasArchetype()) {
+        // If this is a nominal type, check whether it can ever be copyable.
+        if (auto nominal = contextualTy->getAnyNominal()) {
+          if (!nominal->canBeCopyable())
+            isAlwaysNoncopyable = true;
+        } else {
+          // Assume that we could end up with a copyable type somehow.
+        }
+      } else {
+        isAlwaysNoncopyable = true;
+      }
+    }
+
+    if (isAlwaysNoncopyable) {
       IGM.IRGen.noteUseOfTypeMetadata(type);
       return getTypeRefByFunction(IGM, sig, type);
     }

test/IRGen/noncopyable_field_descriptors.swift

@@ -0,0 +1,38 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-ir -o - %s -module-name test \
+// RUN:   -enable-experimental-feature NoncopyableGenerics \
+// RUN:   -enable-experimental-feature NonescapableTypes \
+// RUN:   -parse-as-library \
+// RUN:   -enable-library-evolution \
+// RUN:   > %t/test.irgen
+
+// RUN: %FileCheck %s < %t/test.irgen
+
+@frozen
+public enum ConditionallyCopyable<Wrapped: ~Copyable>: ~Copyable {
+  case none
+  case some(Wrapped)
+}
+
+extension ConditionallyCopyable: Copyable where Wrapped: Copyable { }
+
+@frozen
+public enum NeverCopyable<Wrapped: ~Copyable>: ~Copyable {
+  case none
+  case some(Wrapped)
+}
+
+@frozen
+public struct NonCopyable: ~Copyable { }
+
+// CHECK: @"$s4test1CCMF" = 
+// CHECK-SAME: @"symbolic _____yxG 4test21ConditionallyCopyableOAARiczrlE"
+// CHECK-SAME: @"get_type_metadata Riczl4test21ConditionallyCopyableOyAA03NonC0VG.3"
+// CHECK-SAME: @"symbolic _____yxG 4test21ConditionallyCopyableOAARiczrlE"
+// CHECK-SAME: @"get_type_metadata Riczl4test21ConditionallyCopyableOyAA03NonC0VG.3"
+public class C<T: ~Copyable> {
+  var ccT: ConditionallyCopyable<T> = .none
+  var ccNC: ConditionallyCopyable<NonCopyable> = .none
+  var ncT: ConditionallyCopyable<T> = .none
+  var ncNC: ConditionallyCopyable<NonCopyable> = .none
+}