[cfe] Add inheritance tests for reported problems

Change-Id: I2dfc46f718e7609f3626040eb3542b5441574975
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/135907
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/_fe_analyzer_shared/test/inheritance/data/issue40541.dart

@@ -0,0 +1,29 @@
+/*library: nnbd=true*/
+/*class: A:A<T>,Object*/
+class A<T> {
+  /*member: A.test:void Function()!*/
+  void test() {
+    print(T);
+  }
+}
+
+/*class: B:A<Object?>,B,Object*/
+/*member: B.test:void Function()!*/
+class B extends A<Object?> {}
+
+/*class: C:A<dynamic>,C,Object*/
+/*member: C.test:void Function()!*/
+class C extends A<dynamic> {}
+
+/*class: D1:A<Object?>,B,C,D1,Object*/
+/*member: D1.test:void Function()!*/
+class D1 extends B implements C {}
+
+/*class: D2:A<Object?>,B,C,D2,Object*/
+/*member: D2.test:void Function()!*/
+class D2 extends C implements B {}
+
+void main() {
+  D1().test();
+  D2().test();
+}

pkg/_fe_analyzer_shared/test/inheritance/data/issue40553/main.dart

@@ -0,0 +1,25 @@
+/*library: nnbd=true*/
+import "opt_out.dart";
+import "dart:async";
+
+Type typeOf<X>() => X;
+
+/*class: C:A<FutureOr<int?>!>,C,Object*/
+class C extends A<FutureOr<int?>> {
+  /*member: C.getType:Type* Function()**/
+}
+
+/*class: D:A<FutureOr<int!>!>,D,Object*/
+class D extends A<FutureOr<int>> {
+  /*member: D.getType:Type* Function()**/
+}
+
+/*class: E:A<FutureOr<int?>?>,B,C,E,Object*/
+class E extends B implements C {
+  /*member: E.getType:Type* Function()**/
+}
+
+main() {
+  print(typeOf<FutureOr<int?>>() == E().getType());
+  print(typeOf<FutureOr<int>>() == E().getType());
+}

pkg/_fe_analyzer_shared/test/inheritance/data/issue40553/opt_out.dart

@@ -0,0 +1,15 @@
+// @dart=2.6
+
+/*library: nnbd=false*/
+import "dart:async";
+
+/*class: A:A<T*>,Object*/
+class A<T> {
+  /*member: A.getType:Type* Function()**/
+  Type getType() => T;
+}
+
+/*class: B:A<FutureOr<int*>*>,B,Object*/
+class B extends A<FutureOr<int>> {
+  /*member: B.getType:Type* Function()**/
+}