patch 9.1.1617: Vim9: some error messages can be improved

Problem:  Vim9: some error messages can be improved
Solution: Improve error messages when parsing generic function type
          arguments (Yegappan Lakshmanan).

closes: #17957

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

Author: yegappan

src/ex_docmd.c

@@ -3715,9 +3715,9 @@ find_ex_command(
 		// "&option" can be followed by "->" or "=", check below
 	    }
 
-	    if (*p == '<' && vim9)
+	    if (vim9 && *p == '<')
 	    {
-		// generic function
+		// generic function type args
 		if (skip_generic_func_type_args(&p) == FAIL)
 		{
 		    eap->cmdidx = CMD_SIZE;

src/testdir/test_vim9_generics.vim

@@ -387,6 +387,14 @@ def Test_generic_func_invoke_whitespace_error()
     Fn<number,string>()
   END
   v9.CheckSourceFailure(lines, "E1069: White space required after ',': <number,string>()", 4)
+
+  lines =<< trim END
+    vim9script
+    def Fn<A>()
+    enddef
+    Fn<number> ()
+  END
+  v9.CheckSourceFailure(lines, "E1202: No white space allowed after '>': <number> ()", 4)
 enddef
 
 def Test_generic_func_typename()
@@ -2211,7 +2219,7 @@ def Test_generic_disassemble_generic_obj_method()
     endclass
     disassemble Foo.Fn<number, dict<number>
   END
-  v9.CheckScriptFailure(lines, 'E1553: Missing comma after type in generic function: <number, dict<number>', 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<number, dict<number>", 6)
 
   lines =<< trim END
     vim9script
@@ -2229,7 +2237,7 @@ def Test_generic_disassemble_generic_obj_method()
     endclass
     disassemble Foo.Fn<number,
   END
-  v9.CheckScriptFailure(lines, "E1069: White space required after ','", 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<number,", 6)
 
   lines =<< trim END
     vim9script
@@ -2239,7 +2247,7 @@ def Test_generic_disassemble_generic_obj_method()
     endclass
     disassemble Foo.Fn<
   END
-  v9.CheckScriptFailure(lines, 'E475: Invalid argument: Foo.Fn<', 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<", 6)
 
   lines =<< trim END
     vim9script
@@ -2339,7 +2347,7 @@ def Test_generic_disassemble_generic_class_method()
     endclass
     disassemble Foo.Fn<number, dict<number>
   END
-  v9.CheckScriptFailure(lines, 'E1553: Missing comma after type in generic function: <number, dict<number>', 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<number, dict<number>", 6)
 
   lines =<< trim END
     vim9script
@@ -2349,7 +2357,7 @@ def Test_generic_disassemble_generic_class_method()
     endclass
     disassemble Foo.Fn<number,
   END
-  v9.CheckScriptFailure(lines, "E1069: White space required after ','", 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<number,", 6)
 
   lines =<< trim END
     vim9script
@@ -2359,7 +2367,7 @@ def Test_generic_disassemble_generic_class_method()
     endclass
     disassemble Foo.Fn<
   END
-  v9.CheckScriptFailure(lines, 'E475: Invalid argument: Foo.Fn<', 6)
+  v9.CheckScriptFailure(lines, "E1554: Missing '>' in generic function: Fn<", 6)
 
   lines =<< trim END
     vim9script

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1617,
 /**/
     1616,
 /**/

src/vim9generics.c

@@ -149,6 +149,14 @@ generic_func_find_close_bracket(char_u *start)
 	return NULL;
     }
 
+    if (VIM_ISWHITE(*(p + 1)) && *skipwhite(p + 1) == '(')
+    {
+	// white space not allowed between '>' and '('
+	semsg(_(e_no_white_space_allowed_after_str_str), ">", start);
+	return NULL;
+    }
+
+
     if (type_count == 0)
     {
 	semsg(_(e_empty_type_list_for_generic_function_str), start);
@@ -326,28 +334,35 @@ parse_generic_func_type_args(
 
 	p = skipwhite(p);
 
+	if (*p == NUL || *p == '>')
+	    break;
+
 	// after a type, expect ',' or '>'
-	if (*p != ',' && *p != '>')
+	if (*p != ',')
 	{
 	    semsg(_(e_missing_comma_in_generic_function_str), start);
 	    return NULL;
 	}
 
-	// if there's a comma, require whitespace after it and skip it
-	if (*p == ',')
+	if (*(p + 1) == NUL)
+	    break;
+
+	// Require whitespace after a comma and skip it
+	if (!VIM_ISWHITE(*(p + 1)))
 	{
-	    if (!VIM_ISWHITE(*(p + 1)))
-	    {
-		semsg(_(e_white_space_required_after_str_str), ",", p);
-		return NULL;
-	    }
-	    p++;
+	    semsg(_(e_white_space_required_after_str_str), ",", p);
+	    return NULL;
 	}
+	p++;
     }
 
     // ensure the list of types ends in a closing '>'
     if (*p != '>')
+    {
+	semsg(_(e_missing_closing_angle_bracket_in_generic_function_str),
+		func_name);
 	return NULL;
+    }
 
     // no whitespace allowed before '>'
     if (VIM_ISWHITE(*(p - 1)))