Use getter resultType

Author: EugeneFlesselle

compiler/src/dotty/tools/backend/jvm/BCodeHelpers.scala

@@ -397,13 +397,10 @@ trait BCodeHelpers extends BCodeIdiomatic {
       atPhase(erasurePhase) {
         val memberTpe =
           if (sym.is(Method)) sym.denot.info
-          else
-            val sym0 =
-              if sym.isField && sym.denot.validFor.phaseId > erasurePhase.id then
-                sym.getter.orElse(sym)
-              else
-                sym
-            owner.denot.thisType.memberInfo(sym0)
+          else if sym.denot.validFor.phaseId > erasurePhase.id && sym.isField && sym.getter.exists then
+            // Memoization field of getter entered after erasure, see run/i16069 for an example
+            sym.getter.denot.info.resultType
+          else owner.denot.thisType.memberInfo(sym)
         getGenericSignatureHelper(sym, owner, memberTpe).orNull
       }
     }

tests/run/17069.scala

@@ -1,2 +1,8 @@
+
 class Foo:
   val generic: List[String] = ???
+
+@main def Test =
+  val tpe = classOf[Foo].getDeclaredField("generic").getGenericType()
+  val tpe2 = classOf[Foo].getDeclaredMethod("generic").getGenericReturnType()
+  assert(tpe == tpe2)