patch 9.0.2161: Vim9: not able to use imported interfaces and classes

Problem:  Vim9: not able to use imported interfaces and classes
Solution: Detect imported class/interfaces names correclty

fixes:  #13661
closes: #13685

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

src/testdir/test_vim9_class.vim

@@ -3030,6 +3030,62 @@ def Test_class_import()
   v9.CheckScriptSuccess(lines)
 enddef
 
+" Test for implementing an imported interface
+def Test_implement_imported_interface()
+  var lines =<< trim END
+    vim9script
+    export interface Imp_Intf1
+      def Fn1(): number
+    endinterface
+    export interface Imp_Intf2
+      def Fn2(): number
+    endinterface
+  END
+  writefile(lines, 'Ximportinterface.vim', 'D')
+
+  lines =<< trim END
+    vim9script
+    import './Ximportinterface.vim' as Xintf
+
+    class A implements Xintf.Imp_Intf1, Xintf.Imp_Intf2
+      def Fn1(): number
+        return 10
+      enddef
+      def Fn2(): number
+        return 20
+      enddef
+    endclass
+    var a = A.new()
+    assert_equal(10, a.Fn1())
+    assert_equal(20, a.Fn2())
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
+" Test for extending an imported class
+def Test_extend_imported_class()
+  var lines =<< trim END
+    vim9script
+    export class Imp_C1
+      def Fn1(): number
+        return 5
+      enddef
+    endclass
+  END
+  writefile(lines, 'Xextendimportclass.vim', 'D')
+
+  lines =<< trim END
+    vim9script
+    import './Xextendimportclass.vim' as XClass
+
+    class A extends XClass.Imp_C1
+    endclass
+    var a = A.new()
+    assert_equal(5, a.Fn1())
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 def Test_abstract_class()
   var lines =<< trim END
     vim9script

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2161,
 /**/
     2160,
 /**/

src/vim9class.c

@@ -1304,6 +1304,24 @@ add_classfuncs_objmethods(
     return OK;
 }
 
+/*
+ * Return the end of the class name starting at "arg".  Valid characters in a
+ * class name are alphanumeric characters and "_".  Also handles imported class
+ * names.
+ */
+    static char_u *
+find_class_name_end(char_u *arg)
+{
+    char_u *end = arg;
+
+    while (ASCII_ISALNUM(*end) || *end == '_'
+	    || (*end == '.' && (ASCII_ISALNUM(end[1]) || end[1] == '_')))
+	++end;
+
+    return end;
+}
+
+
 /*
  * Handle ":class" and ":abstract class" up to ":endclass".
  * Handle ":interface" up to ":endinterface".
@@ -1383,7 +1401,8 @@ ex_class(exarg_T *eap)
 		goto early_ret;
 	    }
 	    arg = skipwhite(arg + 7);
-	    char_u *end = find_name_end(arg, NULL, NULL, FNE_CHECK_START);
+
+	    char_u *end = find_class_name_end(arg);
 	    if (!IS_WHITE_OR_NUL(*end))
 	    {
 		semsg(_(e_white_space_required_after_name_str), arg);
@@ -1413,8 +1432,7 @@ ex_class(exarg_T *eap)
 
 	    for (;;)
 	    {
-		char_u *impl_end = find_name_end(arg, NULL, NULL,
-							      FNE_CHECK_START);
+		char_u *impl_end = find_class_name_end(arg);
 		if ((!IS_WHITE_OR_NUL(*impl_end) && *impl_end != ',')
 			|| (*impl_end == ','
 			    && !IS_WHITE_OR_NUL(*(impl_end + 1))))