4 files changed, 18 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/UnCurry.scala b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
index 8a7d30235f..d77c6b54a9 100644
--- a/src/compiler/scala/tools/nsc/transform/UnCurry.scala
+++ b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
@@ -221,7 +221,9 @@ abstract class UnCurry extends InfoTransform
           def mkMethod(owner: Symbol, name: TermName, additionalFlags: FlagSet = NoFlags): DefDef =
             gen.mkMethodFromFunction(localTyper)(fun, owner, name, additionalFlags)
 
-          if (inlineFunctionExpansion) {
+          val canUseDelamdafyMethod = (inConstructorFlag == 0) // Avoiding synthesizing code prone to SI-6666, SI-8363 by using old-style lambda translation
+
+          if (inlineFunctionExpansion || !canUseDelamdafyMethod) {
             val parents = addSerializable(abstractFunctionForFunctionType(fun.tpe))
             val anonClass = fun.symbol.owner newAnonymousFunctionClass(fun.pos, inConstructorFlag) addAnnotation SerialVersionUIDAnnotation
             anonClass setInfo ClassInfoType(parents, newScope, anonClass)
diff --git a/test/files/pos/t8363.flags b/test/files/pos/t8363.flags
new file mode 100644
index 0000000000..48b438ddf8
--- /dev/null
+++ b/test/files/pos/t8363.flags
@@ -0,0 +1 @@
+-Ydelambdafy:method
diff --git a/test/files/pos/t8363.scala b/test/files/pos/t8363.scala
new file mode 100644
index 0000000000..639faf4120
--- /dev/null
+++ b/test/files/pos/t8363.scala
@@ -0,0 +1,7 @@
+class C(a: Any)
+class Test {  
+  def foo: Any = {
+    def form = 0
+    class C1 extends C(() => form)
+  }
+}
diff --git a/test/pending/pos/t8363b.scala b/test/pending/pos/t8363b.scala
new file mode 100644
index 0000000000..393e2a0237
--- /dev/null
+++ b/test/pending/pos/t8363b.scala
@@ -0,0 +1,7 @@
+class C(a: Any)
+class Test {  
+  def foo: Any = {
+    def form = 0
+    class C1 extends C({def x = form; ()})
+  }
+}