vim-patch:8.2.5034: there is no way to get the byte index from a virtual column

Problem:    There is no way to get the byte index from a virtual column.
Solution:   Add virtcol2col(). (Yegappan Lakshmanan, closes vim/vim#10477,
            closes vim/vim#10098)
https://github.com/vim/vim/commit/5a6ec10cc80ab02eeff644ab19b82312630ea855

Cherry-pick tv_check_for_number_arg() from Vim.
Cherry-pick pathshorten() doc change.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index c75d16e4fc..2089415ffa 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -44,6 +44,8 @@ static char e_string_required_for_argument_nr[]
   = N_("E1174: String required for argument %d");
 static char e_non_empty_string_required_for_argument_nr[]
   = N_("E1142: Non-empty string required for argument %d");
+static char e_number_required_for_argument_nr[]
+  = N_("E1210: Number required for argument %d");
 
 bool tv_in_free_unref_items = false;
 
@@ -3830,6 +3832,17 @@ int tv_check_for_nonempty_string_arg(const typval_T *const args, const int idx)
   return OK;
 }
 
+/// Give an error and return FAIL unless "args[idx]" is a number.
+int tv_check_for_number_arg(const typval_T *const args, const int idx)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_PURE
+{
+  if (args[idx].v_type != VAR_NUMBER) {
+    semsg(_(e_number_required_for_argument_nr), idx + 1);
+    return FAIL;
+  }
+  return OK;
+}
+
 /// Get the string value of a "stringish" VimL object.
 ///
 /// @param[in]  tv  Object to get value of.