tests: Added new test from #3315

Also duplicated the tests in `reg_issue3308` to be executed within a function
`b` additionally to the constructor `a`.  This includes the case from #3324,
which is currently commented out in the test.

tests/reg_issue3308/reg_issue3308.fz

@@ -26,6 +26,7 @@
 reg_issue3308 is
 
   f(x ()->unit) =>
+  g(x ()->unit) => _ := x.call
 
   t is
     a is
@@ -47,4 +48,35 @@ reg_issue3308 is
       t(_ unit) =>
       _ := f (t unit)
 
+      # fifth: access outer ref in partial application and call `as_string`
+      redef as_string => "--a--"
+      u(x Any) => say x
+      say (g (u a.this))
+
+    # same thing using a function `b` instead of a constructor `a`:
+    b =>
+
+      # first, b.this is part of the target of the partial call
+      q =>
+      say (f b.this.q)
+
+      # second, b.this is part of the arguments of the partial call
+      r(x _) =>
+      say (f (r b.this))
+
+      # third, b.this is part of the arguments of the partial call and
+      # boxed to Any, see #3315
+      s(x Any) =>
+      say (f (s b.this))
+
+      # fouth, an even simpler version of #3315
+      t(_ unit) =>
+      _ := f (t unit)
+
+      # fifth: access outer ref in partial application and call `as_string`
+      redef as_string => "--b--"
+      u(x Any) => say x
+      # say (g (u b.this))       -- NYI: BUG #3324: does not work yet!
+
   _ := t.a
+  _ := t.b

tests/reg_issue3308/reg_issue3308.fz.expected_out

@@ -1,3 +1,8 @@
 unit
 unit
 unit
+--a--
+unit
+unit
+unit
+unit