patch 9.1.1037: Vim9: confusing error when using abstract method via super

Problem:  Vim9: confusing error when using abstract method via super
Solution: Display an error when an abstract method is invoked using
          super (Ernie Rael)

fixes: #15514
closes: #16478

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/errors.h

@@ -3619,8 +3619,10 @@ EXTERN char e_class_can_only_be_used_in_script[]
 	INIT(= N_("E1429: Class can only be used in a script"));
 EXTERN char e_uninitialized_object_var_reference[]
 	INIT(= N_("E1430: Uninitialized object variable '%s' referenced"));
+EXTERN char e_abstract_method_str_direct[]
+	INIT(= N_("E1431: Abstract method \"%s\" in class \"%s\" cannot be accessed directly"));
 #endif
-// E1431 - E1499 unused (reserved for Vim9 class support)
+// E1432 - E1499 unused (reserved for Vim9 class support)
 EXTERN char e_cannot_mix_positional_and_non_positional_str[]
 	INIT(= N_("E1500: Cannot mix positional and non-positional arguments: %s"));
 EXTERN char e_fmt_arg_nr_unused_str[]

src/testdir/test_vim9_class.vim

@@ -3268,6 +3268,7 @@ def Test_using_base_class()
   v9.CheckSourceSuccess(lines)
 enddef
 
+" Test for using a method from the super class
 def Test_super_dispatch()
   # See #15448 and #15463
   var lines =<< trim END
@@ -3401,6 +3402,160 @@ def Test_super_dispatch()
     assert_equal(['E.SF()', 'D.SF()', 'B.SF()', 'A._H()', 'A.F()', 'F._G()'], call_chain)
   END
   v9.CheckSourceSuccess(lines)
+
+  # problems with method dispatch: super -> abstract
+  # https://github.com/vim/vim/issues/15514
+  lines =<< trim END
+    vim9script
+    abstract class B
+      abstract def ToString(): string
+    endclass
+
+    class C extends B
+      def ToString(): string
+        return super.ToString()
+      enddef
+    endclass
+
+    try
+      defcompile C.ToString
+      call assert_false(1, 'command should have failed')
+    catch
+      call assert_exception('E1431: Abstract method "ToString" in class "B" cannot be accessed directly')
+    endtry
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # problems with method dispatch: super -> abstract -> concrete
+  lines =<< trim END
+    vim9script
+
+    class A
+      def ToString()
+        echo 'A'
+      enddef
+    endclass
+
+    abstract class B extends A
+      abstract def ToString()
+    endclass
+
+    class C extends B
+      def ToString()
+        super.ToString()
+      enddef
+    endclass
+
+    try
+      defcompile C.ToString
+      call assert_false(1, 'command should have failed')
+    catch
+      call assert_exception('E1431: Abstract method "ToString" in class "B" cannot be accessed directly')
+    endtry
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # Invoking a super method and an interface method which have the same name.
+  lines =<< trim END
+    vim9script
+
+    interface I
+      def ToString(): string
+    endinterface
+
+    # Note that A does not implement I.
+    class A
+      def ToString(): string
+        return 'A'
+      enddef
+    endclass
+
+    class B extends A implements I
+      def ToString(): string
+        return super.ToString()
+      enddef
+    endclass
+
+     def TestI(i: I): string
+       return i.ToString()
+     enddef
+
+     assert_equal('A', B.new().ToString())
+     assert_equal('A', TestI(B.new()))
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # super and an abstract class with no abstract methods
+  lines =<< trim END
+    vim9script
+
+    class A
+      def ToString(): string
+        return 'A'
+      enddef
+    endclass
+
+    # An abstract class with no abstract methods.
+    abstract class B extends A
+    endclass
+
+    class C extends B
+      def ToString(): string
+        return super.ToString()
+      enddef
+    endclass
+
+    def TestA(a: A): string
+      return a.ToString()
+    enddef
+
+    def TestB(b: B): string
+      return b.ToString()
+    enddef
+
+    assert_equal('A', C.new().ToString())
+    assert_equal('A', TestA(A.new()))
+    assert_equal('A', TestA(C.new()))
+    assert_equal('A', TestB(C.new()))
+  END
+  v9.CheckSourceSuccess(lines)
+
+  # super and an abstract class with no abstract methods and the initial
+  # implements clause
+  lines =<< trim END
+    vim9script
+
+    interface I
+      def ToString(): string
+    endinterface
+
+    # Note that A does not implement I.
+    class A
+      def ToString(): string
+        return 'A'
+      enddef
+    endclass
+
+    # An abstract class with no abstract methods.
+    abstract class B extends A implements I
+    endclass
+
+    class C extends B implements I
+      def ToString(): string
+        return super.ToString()
+      enddef
+    endclass
+
+    # Note that A.ToString() is different from I.ToString().
+    def TestA(a: A): string
+      return a.ToString()
+    enddef
+
+    assert_equal('A', C.new().ToString())
+    assert_equal('A', TestA(A.new()))
+    assert_equal('A', TestA(C.new()))
+  END
+  v9.CheckSourceSuccess(lines)
 enddef
 
 def Test_class_import()

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1037,
 /**/
     1036,
 /**/

src/vim9expr.c

@@ -373,6 +373,7 @@ compile_class_object_index(cctx_T *cctx, char_u **arg, type_T *type)
 		break;
 	    }
 	}
+
 	ocmember_T  *ocm = NULL;
 	if (ufunc == NULL)
 	{
@@ -405,6 +406,15 @@ compile_class_object_index(cctx_T *cctx, char_u **arg, type_T *type)
 	    }
 	}
 
+	if (is_super && IS_ABSTRACT_METHOD(ufunc))
+	{
+	    // Trying to invoke an abstract method in a super class is not
+	    // allowed.
+	    semsg(_(e_abstract_method_str_direct), ufunc->uf_name,
+		    ufunc->uf_defclass->class_name);
+	    return FAIL;
+	}
+
 	// A private object method can be used only inside the class where it
 	// is defined or in one of the child classes.
 	// A private class method can be used only in the class where it is