patch 8.2.1684: "gF" does not use line number after file in Visual mode

Problem:    "gF" does not use line number after file in Visual mode.
Solution:   Look for ":123" after the Visual area. (closes #6952)

src/findfile.c

@@ -1934,6 +1934,13 @@ grab_file_name(long count, linenr_T *file_lnum)
 
 	if (get_visual_text(NULL, &ptr, &len) == FAIL)
 	    return NULL;
+	// Only recognize ":123" here
+	if (file_lnum != NULL && ptr[len] == ':' && isdigit(ptr[len + 1]))
+	{
+	    char_u *p = ptr + len + 1;
+
+	    *file_lnum = getdigits(&p);
+	}
 	return find_file_name_in_path(ptr, len, options,
 						     count, curbuf->b_ffname);
     }

src/testdir/test_gf.vim

@@ -124,7 +124,7 @@ func Test_gf()
 endfunc
 
 func Test_gf_visual()
-  call writefile([], "Xtest_gf_visual")
+  call writefile(['one', 'two', 'three', 'four'], "Xtest_gf_visual")
   new
   call setline(1, 'XXXtest_gf_visualXXX')
   set hidden
@@ -138,6 +138,25 @@ func Test_gf_visual()
   normal VGgf
   call assert_equal('Xtest_gf_visual', @%)
 
+  " following line number is used for gF
+  bwipe!
+  new
+  call setline(1, 'XXXtest_gf_visual:3XXX')
+  norm! 0ttvt:gF
+  call assert_equal('Xtest_gf_visual', bufname('%'))
+  call assert_equal(3, getcurpos()[1])
+
+  " line number in visual area is used for file name
+  if has('unix')
+    bwipe!
+    call writefile([], "Xtest_gf_visual:3")
+    new
+    call setline(1, 'XXXtest_gf_visual:3XXX')
+    norm! 0ttvtXgF
+    call assert_equal('Xtest_gf_visual:3', bufname('%'))
+  call delete('Xtest_gf_visual:3')
+  endif
+
   bwipe!
   call delete('Xtest_gf_visual')
   set hidden&

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1684,
 /**/
     1683,
 /**/