Let only value types derive from Capabilities

odersky · odersky · commit c870c972fe8b · 2024-06-26T21:33:46.000+02:00
Fixes crash with opaque types reported by @natsukagami
diff --git a/compiler/src/dotty/tools/dotc/cc/CaptureOps.scala b/compiler/src/dotty/tools/dotc/cc/CaptureOps.scala
@@ -272,7 +272,7 @@ extension (tp: Type)
       val sym = tp.typeSymbol
       if sym.isClass then sym.derivesFrom(defn.Caps_Capability)
       else tp.superType.derivesFromCapability
-    case tp: TypeProxy =>
+    case tp: (TypeProxy & ValueType) =>
       tp.superType.derivesFromCapability
     case tp: AndType =>
       tp.tp1.derivesFromCapability || tp.tp2.derivesFromCapability
diff --git a/tests/pos-custom-args/captures/opaque-cap.scala b/tests/pos-custom-args/captures/opaque-cap.scala
@@ -0,0 +1,6 @@
+import language.experimental.captureChecking
+
+trait A extends caps.Capability
+
+object O:
+  opaque type B = A
