Add test for inherited method on functional interface

jbmc/regression/jbmc/lambda-unhandled-types/ChildInterface.java

@@ -0,0 +1 @@
+interface ChildInterface extends ParentInterface {}

jbmc/regression/jbmc/lambda-unhandled-types/ParentInterface.java

@@ -0,0 +1,3 @@
+interface ParentInterface {
+  public int f(int x);
+}

jbmc/regression/jbmc/lambda-unhandled-types/Test.java

@@ -6,5 +6,6 @@ public static void main() {
     StubSuperinterface stubSuperinterface = (x -> x);
     InterfaceDeclaringEquals interfaceDeclaringEquals = (x -> x);
     InterfaceWithDefaults interfaceWithDefaults = (x -> x);
+    ChildInterface inheritedInterface = x -> x;
   }
 }

jbmc/regression/jbmc/lambda-unhandled-types/test.desc

@@ -8,9 +8,11 @@ Test.class
 ^ignoring invokedynamic at java::Test.main:\(\)V address 6 which produces type java::StubSuperinterface which should have exactly one abstract method but actually has 0.
 ^ignoring invokedynamic at java::Test.main:\(\)V address 12 which produces type java::InterfaceDeclaringEquals which should have exactly one abstract method but actually has 2.
 ^ignoring invokedynamic at java::Test.main:\(\)V address 18 which produces type java::InterfaceWithDefaults which should have exactly one abstract method but actually has 2.
+^ignoring invokedynamic at java::Test.main:\(\)V address \d+ which produces type java::ChildInterface which should have exactly one abstract method but actually has 0.
 --
 --
-This exercises four cases that aren't currently supported: stub interfaces, stub
+This exercises five cases that aren't currently supported: stub interfaces, stub
 superinterfaces, interfaces that declare methods also declared on
-java.lang.Object, and interfaces that provide default methods. All we require at
-this point is that jbmc shouldn't crash when these are seen.
+java.lang.Object, interfaces that provide default methods, interfaces that
+inherit their one method. All we require at this point is that jbmc shouldn't
+crash when these are seen.