patch 9.0.1031: Vim9 class is not implemented yet

Problem:    Vim9 class is not implemented yet.
Solution:   Add very basic class support.

src/testdir/test_vim9_class.vim

@@ -0,0 +1,145 @@
+" Test Vim9 classes
+
+source check.vim
+import './vim9.vim' as v9
+
+def Test_class_basic()
+  var lines =<< trim END
+      class NotWorking
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1316:')
+
+  lines =<< trim END
+      vim9script
+      class notWorking
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1314:')
+
+  lines =<< trim END
+      vim9script
+      class Not@working
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1315:')
+
+  lines =<< trim END
+      vim9script
+      abstract noclass Something
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E475:')
+
+  lines =<< trim END
+      vim9script
+      abstract classy Something
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E475:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+      endcl
+  END
+  v9.CheckScriptFailure(lines, 'E1065:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+      endclass school's out 
+  END
+  v9.CheckScriptFailure(lines, 'E488:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+      endclass | echo 'done'
+  END
+  v9.CheckScriptFailure(lines, 'E488:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1317:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this.
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1317:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this .count
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1317:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this. count
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1317:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this.count: number
+        that.count
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1318: Not a valid command in a class: that.count')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this.count
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1022:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this.count : number
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1059:')
+
+  lines =<< trim END
+      vim9script
+      class Something
+        this.count:number
+      endclass
+  END
+  v9.CheckScriptFailure(lines, 'E1069:')
+
+  lines =<< trim END
+      vim9script
+
+      class TextPosition
+        this.lnum: number
+	this.col: number
+      endclass
+
+      # # FIXME: this works but leaks memory
+      # # use the automatically generated new() method
+      # var pos = TextPosition.new(2, 12)
+      # assert_equal(2, pos.lnum)
+      # assert_equal(12, pos.col)
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
+
+" vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker