Merge #6114 'Partial string handling refactoring'.

31 files changed, 1395 insertions, 1158 deletions

diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 4d150c3230..e33e002787 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1373,17 +1373,17 @@ void getvcols(win_T *wp, pos_T *pos1, pos_T *pos2, colnr_T *left,
 
 /// skipwhite: skip over ' ' and '\t'.
 ///
-/// @param q
+/// @param[in]  q  String to skip in.
 ///
 /// @return Pointer to character after the skipped whitespace.
-char_u* skipwhite(char_u *q)
+char_u *skipwhite(const char_u *q)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  char_u *p = q;
+  const char_u *p = q;
   while (ascii_iswhite(*p)) {
-    // skip to next non-white
     p++;
   }
-  return p;
+  return (char_u *)p;
 }
 
 /// skip over digits
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 53540d21d4..9a8ff21263 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -1859,8 +1859,9 @@ static bool check_compl_option(bool dict_opt)
       : (*curbuf->b_p_tsr == NUL && *p_tsr == NUL)) {
     ctrl_x_mode = 0;
     edit_submode = NULL;
-    msg_attr(dict_opt ? (char_u *)_("'dictionary' option is empty")
-             : (char_u *)_("'thesaurus' option is empty"), hl_attr(HLF_E));
+    msg_attr((dict_opt
+              ? _("'dictionary' option is empty")
+              : _("'thesaurus' option is empty")), hl_attr(HLF_E));
     if (emsg_silent == 0) {
       vim_beep(BO_COMPL);
       setcursor();
@@ -4801,9 +4802,9 @@ static int ins_complete(int c, bool enable_pum)
   if (!shortmess(SHM_COMPLETIONMENU)) {
     if (edit_submode_extra != NULL) {
       if (!p_smd) {
-        msg_attr(edit_submode_extra,
-                 edit_submode_highl < HLF_COUNT
-                 ? hl_attr(edit_submode_highl) : 0);
+        msg_attr((const char *)edit_submode_extra,
+                 (edit_submode_highl < HLF_COUNT
+                  ? hl_attr(edit_submode_highl) : 0));
       }
     } else {
       msg_clr_cmdline();  // necessary for "noshowmode"
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index bbb6565509..d98df6a06e 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -1454,13 +1454,13 @@ void ex_let(exarg_T *eap)
   if (*expr != '=' && !(vim_strchr((char_u *)"+-.", *expr) != NULL
                         && expr[1] == '=')) {
     // ":let" without "=": list variables
-    if (*arg == '[')
+    if (*arg == '[') {
       EMSG(_(e_invarg));
-    else if (!ends_excmd(*arg))
-      /* ":let var1 var2" */
-      arg = list_arg_vars(eap, arg, &first);
-    else if (!eap->skip) {
-      /* ":let" */
+    } else if (!ends_excmd(*arg)) {
+      // ":let var1 var2"
+      arg = (char_u *)list_arg_vars(eap, (const char *)arg, &first);
+    } else if (!eap->skip) {
+      // ":let"
       list_glob_vars(&first);
       list_buf_vars(&first);
       list_win_vars(&first);
@@ -1644,7 +1644,8 @@ static char_u *skip_var_one(char_u *arg)
  * List variables for hashtab "ht" with prefix "prefix".
  * If "empty" is TRUE also list NULL strings as empty strings.
  */
-static void list_hashtable_vars(hashtab_T *ht, char_u *prefix, int empty, int *first)
+static void list_hashtable_vars(hashtab_T *ht, const char *prefix, int empty,
+                                int *first)
 {
   hashitem_T  *hi;
   dictitem_T  *di;
@@ -1653,11 +1654,12 @@ static void list_hashtable_vars(hashtab_T *ht, char_u *prefix, int empty, int *f
   todo = (int)ht->ht_used;
   for (hi = ht->ht_array; todo > 0 && !got_int; ++hi) {
     if (!HASHITEM_EMPTY(hi)) {
-      --todo;
+      todo--;
       di = HI2DI(hi);
       if (empty || di->di_tv.v_type != VAR_STRING
-          || di->di_tv.vval.v_string != NULL)
+          || di->di_tv.vval.v_string != NULL) {
         list_one_var(di, prefix, first);
+      }
     }
   }
 }
@@ -1667,7 +1669,7 @@ static void list_hashtable_vars(hashtab_T *ht, char_u *prefix, int empty, int *f
  */
 static void list_glob_vars(int *first)
 {
-  list_hashtable_vars(&globvarht, (char_u *)"", TRUE, first);
+  list_hashtable_vars(&globvarht, "", true, first);
 }
 
 /*
@@ -1675,14 +1677,13 @@ static void list_glob_vars(int *first)
  */
 static void list_buf_vars(int *first)
 {
-  char_u numbuf[NUMBUFLEN];
+  char numbuf[NUMBUFLEN];
 
-  list_hashtable_vars(&curbuf->b_vars->dv_hashtab, (char_u *)"b:",
-      TRUE, first);
+  list_hashtable_vars(&curbuf->b_vars->dv_hashtab, "b:", true, first);
 
-  sprintf((char *)numbuf, "%" PRId64, (int64_t)curbuf->b_changedtick);
-  list_one_var_a((char_u *)"b:", (char_u *)"changedtick", VAR_NUMBER,
-      numbuf, first);
+  snprintf(numbuf, sizeof(numbuf), "%d", curbuf->b_changedtick);
+  list_one_var_a("b:", "changedtick", sizeof("changedtick") - 1, VAR_NUMBER,
+                 numbuf, first);
 }
 
 /*
@@ -1690,8 +1691,7 @@ static void list_buf_vars(int *first)
  */
 static void list_win_vars(int *first)
 {
-  list_hashtable_vars(&curwin->w_vars->dv_hashtab,
-      (char_u *)"w:", TRUE, first);
+  list_hashtable_vars(&curwin->w_vars->dv_hashtab, "w:", true, first);
 }
 
 /*
@@ -1699,8 +1699,7 @@ static void list_win_vars(int *first)
  */
 static void list_tab_vars(int *first)
 {
-  list_hashtable_vars(&curtab->tp_vars->dv_hashtab,
-      (char_u *)"t:", TRUE, first);
+  list_hashtable_vars(&curtab->tp_vars->dv_hashtab, "t:", true, first);
 }
 
 /*
@@ -1708,7 +1707,7 @@ static void list_tab_vars(int *first)
  */
 static void list_vim_vars(int *first)
 {
-  list_hashtable_vars(&vimvarht, (char_u *)"v:", FALSE, first);
+  list_hashtable_vars(&vimvarht, "v:", false, first);
 }
 
 /*
@@ -1716,9 +1715,9 @@ static void list_vim_vars(int *first)
  */
 static void list_script_vars(int *first)
 {
-  if (current_SID > 0 && current_SID <= ga_scripts.ga_len)
-    list_hashtable_vars(&SCRIPT_VARS(current_SID),
-        (char_u *)"s:", FALSE, first);
+  if (current_SID > 0 && current_SID <= ga_scripts.ga_len) {
+    list_hashtable_vars(&SCRIPT_VARS(current_SID), "s:", false, first);
+  }
 }
 
 /*
@@ -1726,36 +1725,37 @@ static void list_script_vars(int *first)
  */
 static void list_func_vars(int *first)
 {
-  if (current_funccal != NULL)
-    list_hashtable_vars(&current_funccal->l_vars.dv_hashtab,
-        (char_u *)"l:", FALSE, first);
+  if (current_funccal != NULL) {
+    list_hashtable_vars(&current_funccal->l_vars.dv_hashtab, "l:", false,
+                        first);
+  }
 }
 
 /*
  * List variables in "arg".
  */
-static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first)
+static const char *list_arg_vars(exarg_T *eap, const char *arg, int *first)
 {
   int error = FALSE;
   int len;
-  char_u      *name;
-  char_u      *name_start;
-  char_u      *arg_subsc;
-  char_u      *tofree;
+  const char *name;
+  const char *name_start;
   typval_T tv;
 
   while (!ends_excmd(*arg) && !got_int) {
     if (error || eap->skip) {
-      arg = find_name_end(arg, NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
+      arg = (const char *)find_name_end((char_u *)arg, NULL, NULL,
+                                        FNE_INCL_BR | FNE_CHECK_START);
       if (!ascii_iswhite(*arg) && !ends_excmd(*arg)) {
         emsg_severe = TRUE;
         EMSG(_(e_trailing));
         break;
       }
     } else {
-      /* get_name_len() takes care of expanding curly braces */
+      // get_name_len() takes care of expanding curly braces
       name_start = name = arg;
-      len = get_name_len(&arg, &tofree, TRUE, TRUE);
+      char *tofree;
+      len = get_name_len(&arg, &tofree, true, true);
       if (len <= 0) {
         /* This is mainly to keep test 49 working: when expanding
          * curly braces fails overrule the exception error message. */
@@ -1769,14 +1769,15 @@ static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first)
         if (tofree != NULL) {
           name = tofree;
         }
-        if (get_var_tv(name, len, &tv, NULL, true, false) == FAIL) {
+        if (get_var_tv((const char *)name, len, &tv, NULL, true, false)
+            == FAIL) {
           error = true;
         } else {
           // handle d.key, l[idx], f(expr)
-          arg_subsc = arg;
-          if (handle_subscript(&arg, &tv, TRUE, TRUE) == FAIL)
-            error = TRUE;
-          else {
+          const char *const arg_subsc = arg;
+          if (handle_subscript(&arg, &tv, true, true) == FAIL) {
+            error = true;
+          } else {
             if (arg == arg_subsc && len == 2 && name[1] == ':') {
               switch (*name) {
               case 'g': list_glob_vars(first); break;
@@ -1790,17 +1791,15 @@ static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first)
                 EMSG2(_("E738: Can't list variables for %s"), name);
               }
             } else {
-              int c;
-
-              char_u *s = (char_u *) encode_tv2echo(&tv, NULL);
-              c = *arg;
-              *arg = NUL;
-              list_one_var_a((char_u *)"",
-                  arg == arg_subsc ? name : name_start,
-                  tv.v_type,
-                  s == NULL ? (char_u *)"" : s,
-                  first);
-              *arg = c;
+              char *const s = encode_tv2echo(&tv, NULL);
+              const char *const used_name = (arg == arg_subsc
+                                             ? name
+                                             : name_start);
+              const ptrdiff_t name_size = (used_name == tofree
+                                           ? (ptrdiff_t)strlen(used_name)
+                                           : (arg - used_name));
+              list_one_var_a("", used_name, name_size,
+                             tv.v_type, s == NULL ? "" : s, first);
               xfree(s);
             }
             clear_tv(&tv);
@@ -1811,7 +1810,7 @@ static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first)
       xfree(tofree);
     }
 
-    arg = skipwhite(arg);
+    arg = (const char *)skipwhite((const char_u *)arg);
   }
 
   return arg;
@@ -1831,9 +1830,7 @@ ex_let_one (
     char_u *op                /* "+", "-", "."  or NULL*/
 )
 {
-  int c1;
   char_u      *name;
-  char_u      *p;
   char_u      *arg_end = NULL;
   int len;
   int opt_flags;
@@ -1847,18 +1844,18 @@ ex_let_one (
     ++arg;
     name = arg;
     len = get_env_len(&arg);
-    if (len == 0)
+    if (len == 0) {
       EMSG2(_(e_invarg2), name - 1);
-    else {
-      if (op != NULL && (*op == '+' || *op == '-'))
+    } else {
+      if (op != NULL && (*op == '+' || *op == '-')) {
         EMSG2(_(e_letwrong), op);
-      else if (endchars != NULL
-               && vim_strchr(endchars, *skipwhite(arg)) == NULL)
+      } else if (endchars != NULL
+                 && vim_strchr(endchars, *skipwhite(arg)) == NULL) {
         EMSG(_(e_letunexp));
-      else if (!check_secure()) {
-        c1 = name[len];
+      } else if (!check_secure()) {
+        const char_u c1 = name[len];
         name[len] = NUL;
-        p = get_tv_string_chk(tv);
+        char_u *p = get_tv_string_chk(tv);
         if (p != NULL && op != NULL && *op == '.') {
           char *s = vim_getenv((char *)name);
 
@@ -1882,43 +1879,41 @@ ex_let_one (
         xfree(tofree);
       }
     }
-  }
-  /*
-   * ":let &option = expr": Set option value.
-   * ":let &l:option = expr": Set local option value.
-   * ":let &g:option = expr": Set global option value.
-   */
-  else if (*arg == '&') {
-    /* Find the end of the name. */
-    p = find_option_end(&arg, &opt_flags);
-    if (p == NULL || (endchars != NULL
-                      && vim_strchr(endchars, *skipwhite(p)) == NULL))
+  // ":let &option = expr": Set option value.
+  // ":let &l:option = expr": Set local option value.
+  // ":let &g:option = expr": Set global option value.
+  } else if (*arg == '&') {
+    // Find the end of the name.
+    char *const p = (char *)find_option_end((const char **)&arg, &opt_flags);
+    if (p == NULL
+        || (endchars != NULL
+            && vim_strchr(endchars, *skipwhite((const char_u *)p)) == NULL)) {
       EMSG(_(e_letunexp));
-    else {
+    } else {
       long n;
       int opt_type;
       long numval;
-      char_u      *stringval = NULL;
-      char_u      *s;
+      char_u *stringval = NULL;
+      char_u *s;
 
-      c1 = *p;
+      const char c1 = *p;
       *p = NUL;
 
       n = get_tv_number(tv);
       s = get_tv_string_chk(tv);            /* != NULL if number or string */
       if (s != NULL && op != NULL && *op != '=') {
-        opt_type = get_option_value(arg, &numval,
-            &stringval, opt_flags);
+        opt_type = get_option_value(arg, &numval, &stringval, opt_flags);
         if ((opt_type == 1 && *op == '.')
-            || (opt_type == 0 && *op != '.'))
+            || (opt_type == 0 && *op != '.')) {
           EMSG2(_(e_letwrong), op);
-        else {
-          if (opt_type == 1) {          /* number */
-            if (*op == '+')
+        } else {
+          if (opt_type == 1) {  // number
+            if (*op == '+') {
               n = numval + n;
-            else
+            } else {
               n = numval - n;
-          } else if (opt_type == 0 && stringval != NULL) {     /* string */
+            }
+          } else if (opt_type == 0 && stringval != NULL) {  // string
             s = concat_str(stringval, s);
             xfree(stringval);
             stringval = s;
@@ -1927,7 +1922,7 @@ ex_let_one (
       }
       if (s != NULL) {
         set_option_value(arg, n, s, opt_flags);
-        arg_end = p;
+        arg_end = (char_u *)p;
       }
       *p = c1;
       xfree(stringval);
@@ -1947,7 +1942,7 @@ ex_let_one (
       char_u      *ptofree = NULL;
       char_u      *s;
 
-      p = get_tv_string_chk(tv);
+      char_u *p = get_tv_string_chk(tv);
       if (p != NULL && op != NULL && *op == '.') {
         s = get_reg_contents(*arg == '@' ? '"' : *arg, kGRegExprSrc);
         if (s != NULL) {
@@ -1969,7 +1964,7 @@ ex_let_one (
   else if (eval_isnamec1(*arg) || *arg == '{') {
     lval_T lv;
 
-    p = get_lval(arg, tv, &lv, FALSE, FALSE, 0, FNE_CHECK_START);
+    char_u *const p = get_lval(arg, tv, &lv, false, false, 0, FNE_CHECK_START);
     if (p != NULL && lv.ll_name != NULL) {
       if (endchars != NULL && vim_strchr(endchars, *skipwhite(p)) == NULL)
         EMSG(_(e_letunexp));
@@ -2079,9 +2074,11 @@ get_lval (
 
   cc = *p;
   *p = NUL;
-  v = find_var(lp->ll_name, &ht, flags & GLV_NO_AUTOLOAD);
-  if (v == NULL && !quiet)
+  v = find_var((const char *)lp->ll_name, STRLEN(lp->ll_name), &ht,
+               flags & GLV_NO_AUTOLOAD);
+  if (v == NULL && !quiet) {
     EMSG2(_(e_undefvar), lp->ll_name);
+  }
   *p = cc;
   if (v == NULL)
     return NULL;
@@ -2341,7 +2338,7 @@ static void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv, int copy, ch
 
         // handle +=, -= and .=
         di = NULL;
-        if (get_var_tv(lp->ll_name, (int)STRLEN(lp->ll_name),
+        if (get_var_tv((const char *)lp->ll_name, (int)STRLEN(lp->ll_name),
                        &tv, &di, true, false) == OK) {
           if ((di == NULL
                || (!var_check_ro(di->di_flags, lp->ll_name, false)
@@ -2817,7 +2814,7 @@ void ex_call(exarg_T *eap)
   // contents. For VAR_PARTIAL get its partial, unless we already have one
   // from trans_function_name().
   len = (int)STRLEN(tofree);
-  name = deref_func_name(tofree, &len,
+  name = deref_func_name((const char *)tofree, &len,
                          partial != NULL ? NULL : &partial, false);
 
   /* Skip white space to allow ":call func ()".  Not good, but required for
@@ -2855,9 +2852,10 @@ void ex_call(exarg_T *eap)
       break;
     }
 
-    /* Handle a function returning a Funcref, Dictionary or List. */
-    if (handle_subscript(&arg, &rettv, !eap->skip, TRUE) == FAIL) {
-      failed = TRUE;
+    // Handle a function returning a Funcref, Dictionary or List.
+    if (handle_subscript((const char **)&arg, &rettv, !eap->skip, true)
+        == FAIL) {
+      failed = true;
       break;
     }
 
@@ -3046,7 +3044,8 @@ int do_unlet(char_u *name, int forceit)
   dict_T      *d;
   dictitem_T  *di;
   dict_T *dict;
-  ht = find_var_ht_dict(name, &varname, &dict);
+  ht = find_var_ht_dict((const char *)name, STRLEN(name),
+                        (const char **)&varname, &dict);
 
   if (ht != NULL && *varname != NUL) {
     if (ht == &globvarht) {
@@ -3057,7 +3056,7 @@ int do_unlet(char_u *name, int forceit)
     } else if (ht == &compat_hashtab) {
         d = &vimvardict;
     } else {
-      di = find_var_in_ht(ht, *name, (char_u *)"", false);
+      di = find_var_in_ht(ht, *name, "", 0, false);
       d = di->di_tv.vval.v_dict;
     }
     if (d == NULL) {
@@ -3117,18 +3116,19 @@ static int do_lock_var(lval_T *lp, char_u *name_end, int deep, int lock)
     cc = *name_end;
     *name_end = NUL;
 
-    /* Normal name or expanded name. */
-    if (check_changedtick(lp->ll_name))
+    // Normal name or expanded name.
+    if (check_changedtick(lp->ll_name)) {
       ret = FAIL;
-    else {
-      di = find_var(lp->ll_name, NULL, TRUE);
-      if (di == NULL)
+    } else {
+      di = find_var((const char *)lp->ll_name, STRLEN(lp->ll_name), NULL, true);
+      if (di == NULL) {
         ret = FAIL;
-      else {
-        if (lock)
+      } else {
+        if (lock) {
           di->di_flags |= DI_FLAGS_LOCK;
-        else
+        } else {
           di->di_flags &= ~DI_FLAGS_LOCK;
+        }
         item_lock(&di->di_tv, deep, lock);
       }
     }
@@ -4305,9 +4305,10 @@ static int eval7(
     break;
 
   // Option value: &name
-  case '&':   ret = get_option_tv(arg, rettv, evaluate);
+  case '&': {
+    ret = get_option_tv((const char **)arg, rettv, evaluate);
     break;
-
+  }
   // Environment variable: $VAR.
   case '$':   ret = get_env_tv(arg, rettv, evaluate);
     break;
@@ -4343,7 +4344,7 @@ static int eval7(
     // Must be a variable or function name.
     // Can also be a curly-braces kind of name: {expr}.
     s = *arg;
-    len = get_name_len(arg, &alias, evaluate, true);
+    len = get_name_len((const char **)arg, (char **)&alias, evaluate, true);
     if (alias != NULL) {
       s = alias;
     }
@@ -4355,7 +4356,7 @@ static int eval7(
         partial_T *partial;
         // If "s" is the name of a variable of type VAR_FUNC
         // use its contents.
-        s = deref_func_name(s, &len, &partial, !evaluate);
+        s = deref_func_name((const char *)s, &len, &partial, !evaluate);
 
         // Invoke the function.
         ret = get_func_tv(s, len, rettv, arg,
@@ -4380,7 +4381,7 @@ static int eval7(
           ret = FAIL;
         }
       } else if (evaluate) {
-        ret = get_var_tv(s, len, rettv, NULL, true, false);
+        ret = get_var_tv((const char *)s, len, rettv, NULL, true, false);
       } else {
         ret = OK;
       }
@@ -4393,7 +4394,7 @@ static int eval7(
   // Handle following '[', '(' and '.' for expr[expr], expr.name,
   // expr(expr).
   if (ret == OK) {
-    ret = handle_subscript(arg, rettv, evaluate, true);
+    ret = handle_subscript((const char **)arg, rettv, evaluate, true);
   }
 
   // Apply logical NOT and unary '-', from right to left, ignore '+'.
@@ -4694,35 +4695,32 @@ eval_index (
   return OK;
 }
 
-/*
- * Get an option value.
- * "arg" points to the '&' or '+' before the option name.
- * "arg" is advanced to character after the option name.
- * Return OK or FAIL.
- */
-static int 
-get_option_tv (
-    char_u **arg,
-    typval_T *rettv,     /* when NULL, only check if option exists */
-    int evaluate
-)
+/// Get an option value
+///
+/// @param[in,out]  arg  Points to the '&' or '+' before the option name. Is
+///                      advanced to the character after the option name.
+/// @param[out]  rettv  Location where result is saved.
+/// @param[in]  evaluate  If not true, rettv is not populated.
+///
+/// @return OK or FAIL.
+static int get_option_tv(const char **const arg, typval_T *const rettv,
+                         const bool evaluate)
+  FUNC_ATTR_NONNULL_ARG(1)
 {
-  char_u      *option_end;
   long numval;
   char_u      *stringval;
   int opt_type;
   int c;
-  int working = (**arg == '+');              /* has("+option") */
+  bool working = (**arg == '+');  // has("+option")
   int ret = OK;
   int opt_flags;
 
-  /*
-   * Isolate the option name and find its value.
-   */
-  option_end = find_option_end(arg, &opt_flags);
+  // Isolate the option name and find its value.
+  char *option_end = (char *)find_option_end(arg, &opt_flags);
   if (option_end == NULL) {
-    if (rettv != NULL)
+    if (rettv != NULL) {
       EMSG2(_("E112: Option name missing: %s"), *arg);
+    }
     return FAIL;
   }
 
@@ -4733,8 +4731,8 @@ get_option_tv (
 
   c = *option_end;
   *option_end = NUL;
-  opt_type = get_option_value(*arg, &numval,
-      rettv == NULL ? NULL : &stringval, opt_flags);
+  opt_type = get_option_value((char_u *)(*arg), &numval,
+                              rettv == NULL ? NULL : &stringval, opt_flags);
 
   if (opt_type == -3) {                 /* invalid name */
     if (rettv != NULL)
@@ -6994,40 +6992,45 @@ static VimLFuncDef *find_internal_func(const char *const name)
   return find_internal_func_gperf(name, len);
 }
 
-/// Check if "name" is a variable of type VAR_FUNC.  If so, return the function
-/// name it contains, otherwise return "name".
-/// If "partialp" is not NULL, and "name" is of type VAR_PARTIAL also set
-/// "partialp".
-static char_u *deref_func_name(
-    char_u *name, int *lenp,
-    partial_T **partialp, bool no_autoload
-)
+/// Return name of the function corresponding to `name`
+///
+/// If `name` points to variable that is either a function or partial then
+/// corresponding function name is returned. Otherwise it returns `name` itself.
+///
+/// @param[in]  name  Function name to check.
+/// @param[in,out]  lenp  Location where length of the returned name is stored.
+///                       Must be set to the length of the `name` argument.
+/// @param[out]  partialp  Location where partial will be stored if found
+///                        function appears to be a partial. May be NULL if this
+///                        is not needed.
+/// @param[in]  no_autoload  If true, do not source autoload scripts if function
+///                          was not found.
+///
+/// @return name of the function.
+static char_u *deref_func_name(const char *name, int *lenp,
+                               partial_T **const partialp, bool no_autoload)
+  FUNC_ATTR_NONNULL_ARG(1, 2)
 {
-  dictitem_T  *v;
-  int cc;
   if (partialp != NULL) {
     *partialp = NULL;
   }
 
-  cc = name[*lenp];
-  name[*lenp] = NUL;
-  v = find_var(name, NULL, no_autoload);
-  name[*lenp] = cc;
+  dictitem_T *const v = find_var(name, (size_t)(*lenp), NULL, no_autoload);
   if (v != NULL && v->di_tv.v_type == VAR_FUNC) {
-    if (v->di_tv.vval.v_string == NULL) {
+    if (v->di_tv.vval.v_string == NULL) {  // just in case
       *lenp = 0;
-      return (char_u *)"";              /* just in case */
+      return (char_u *)"";
     }
     *lenp = (int)STRLEN(v->di_tv.vval.v_string);
     return v->di_tv.vval.v_string;
   }
 
   if (v != NULL && v->di_tv.v_type == VAR_PARTIAL) {
-    partial_T *pt = v->di_tv.vval.v_partial;
+    partial_T *const pt = v->di_tv.vval.v_partial;
 
-    if (pt == NULL) {
+    if (pt == NULL) {  // just in case
       *lenp = 0;
-      return (char_u *)"";  // just in case
+      return (char_u *)"";
     }
     if (partialp != NULL) {
       *partialp = pt;
@@ -7036,7 +7039,7 @@ static char_u *deref_func_name(
     return pt->pt_name;
   }
 
-  return name;
+  return (char_u *)name;
 }
 
 /*
@@ -7103,33 +7106,48 @@ get_func_tv (
   return ret;
 }
 
-#define ERROR_UNKNOWN   0
-#define ERROR_TOOMANY   1
-#define ERROR_TOOFEW    2
-#define ERROR_SCRIPT    3
-#define ERROR_DICT      4
-#define ERROR_NONE      5
-#define ERROR_OTHER     6
-#define ERROR_BOTH      7
+typedef enum {
+  ERROR_UNKNOWN = 0,
+  ERROR_TOOMANY,
+  ERROR_TOOFEW,
+  ERROR_SCRIPT,
+  ERROR_DICT,
+  ERROR_NONE,
+  ERROR_OTHER,
+  ERROR_BOTH,
+} FnameTransError;
+
 #define FLEN_FIXED 40
 
-/// In a script change <SID>name() and s:name() to K_SNR 123_name().
-/// Change <SNR>123_name() to K_SNR 123_name().
-/// Use "fname_buf[FLEN_FIXED + 1]" when it fits, otherwise allocate memory
-/// (slow).
-static char_u *
-fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *error) {
-  int llen;
+/// In a script transform script-local names into actually used names
+///
+/// Transforms "<SID>" and "s:" prefixes to `K_SNR {N}` (e.g. K_SNR "123") and
+/// "<SNR>" prefix to `K_SNR`. Uses `fname_buf` buffer that is supposed to have
+/// #FLEN_FIXED + 1 length when it fits, otherwise it allocates memory.
+///
+/// @param[in]  name  Name to transform.
+/// @param  fname_buf  Buffer to save resulting function name to, if it fits.
+///                    Must have at least #FLEN_FIXED + 1 length.
+/// @param[out]  tofree  Location where pointer to an allocated memory is saved
+///                      in case result does not fit into fname_buf.
+/// @param[out]  error  Location where error type is saved, @see
+///                     FnameTransError.
+///
+/// @return transformed name: either `fname_buf` or a pointer to an allocated
+///         memory.
+static char_u *fname_trans_sid(const char_u *const name,
+                               char_u *const fname_buf,
+                               char_u **const tofree, int *const error)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
+{
   char_u *fname;
-  int i;
-
-  llen = eval_fname_script(name);
+  const int llen = eval_fname_script((const char *)name);
   if (llen > 0) {
     fname_buf[0] = K_SPECIAL;
     fname_buf[1] = KS_EXTRA;
     fname_buf[2] = (int)KE_SNR;
-    i = 3;
-    if (eval_fname_sid(name)) {  // "<SID>" or "s:"
+    int i = 3;
+    if (eval_fname_sid((const char *)name)) {  // "<SID>" or "s:"
       if (current_SID <= 0) {
         *error = ERROR_SCRIPT;
       } else {
@@ -7152,7 +7170,7 @@ fname_trans_sid(char_u *name, char_u *fname_buf, char_u **tofree, int *error) {
       }
     }
   } else {
-    fname = name;
+    fname = (char_u *)name;
   }
 
   return fname;
@@ -7235,10 +7253,8 @@ call_func(
     rettv->vval.v_number = 0;
     error = ERROR_UNKNOWN;
 
-    if (!builtin_function(rfname, -1)) {
-      /*
-       * User defined function.
-       */
+    if (!builtin_function((const char *)rfname, -1)) {
+      // User defined function.
       fp = find_func(rfname);
 
       /* Trigger FuncUndefined event, may load the function. */
@@ -7248,9 +7264,10 @@ call_func(
         /* executed an autocommand, search for the function again */
         fp = find_func(rfname);
       }
-      /* Try loading a package. */
-      if (fp == NULL && script_autoload(rfname, TRUE) && !aborting()) {
-        /* loaded a package, search for the function again */
+      // Try loading a package.
+      if (fp == NULL && script_autoload((const char *)rfname, STRLEN(rfname),
+                                        true) && !aborting()) {
+        // Loaded a package, search for the function again.