patch 9.0.2088: Vim9: still allows abstract static methods

Problem:  Vim9: still allows abstract static methods
          (after v9.0.2084, v9.0.2085 and v9.0.2087)
Solution: Disallow abstract static methods

closes: #13479

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: yegappan

src/testdir/test_vim9_class.vim

@@ -5607,15 +5607,13 @@ def Test_abstract_method()
   v9.CheckSourceFailure(lines, 'E1371: Abstract must be followed by "def"', 3)
 
   # Use a static abstract method
-  # TODO: this does not fail, so skip it for now
-
-  # lines =<< trim END
-  #   vim9script
-  #   abstract class A
-  #     abstract static def Foo(): number
-  #   endclass
-  # END
-  # v9.CheckSourceFailure(lines, 'E1371: Abstract must be followed by "def"', 3)
+  lines =<< trim END
+    vim9script
+    abstract class A
+      abstract static def Foo(): number
+    endclass
+  END
+  v9.CheckSourceFailure(lines, 'E1371: Abstract must be followed by "def"', 3)
 
   # Type mismatch between abstract method and concrete method
   lines =<< trim END

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2088,
 /**/
     2087,
 /**/

src/vim9class.c

@@ -1557,13 +1557,6 @@ ex_class(exarg_T *eap)
 		break;
 	    }
 
-	    p = skipwhite(pa + 8);
-	    if (STRNCMP(p, "def", 3) != 0 && STRNCMP(p, "static", 6) != 0)
-	    {
-		emsg(_(e_abstract_must_be_followed_by_def));
-		break;
-	    }
-
 	    if (!is_class)
 	    {
 		// "abstract" not supported in an interface
@@ -1577,6 +1570,13 @@ ex_class(exarg_T *eap)
 		break;
 	    }
 
+	    p = skipwhite(pa + 8);
+	    if (STRNCMP(p, "def", 3) != 0)
+	    {
+		emsg(_(e_abstract_must_be_followed_by_def));
+		break;
+	    }
+
 	    abstract_method = TRUE;
 	}