refactor: reduce number of unique char casts (#15995)

29 files changed, 133 insertions, 140 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 3a38a14cdd..31d44c68bf 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -1903,7 +1903,7 @@ Integer nvim_buf_add_highlight(Buffer buffer, Integer ns_id, String hl_group, In
 
   int hl_id = 0;
   if (hl_group.size > 0) {
-    hl_id = syn_check_group((char_u *)hl_group.data, (int)hl_group.size);
+    hl_id = syn_check_group(hl_group.data, (int)hl_group.size);
   } else {
     return ns_id;
   }
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index aed87048ce..b2529db5be 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -1559,7 +1559,7 @@ int object_to_hl_id(Object obj, const char *what, Error *err)
 {
   if (obj.type == kObjectTypeString) {
     String str = obj.data.string;
-    return str.size ? syn_check_group((char_u *)str.data, (int)str.size) : 0;
+    return str.size ? syn_check_group(str.data, (int)str.size) : 0;
   } else if (obj.type == kObjectTypeInteger) {
     return MAX((int)obj.data.integer, 0);
   } else {
@@ -1593,7 +1593,7 @@ HlMessage parse_hl_msg(Array chunks, Error *err)
       String hl = chunk.items[1].data.string;
       if (hl.size > 0) {
         // TODO(bfredl): use object_to_hl_id and allow integer
-        int hl_id = syn_check_group((char_u *)hl.data, (int)hl.size);
+        int hl_id = syn_check_group(hl.data, (int)hl.size);
         attr = hl_id > 0 ? syn_id2attr(hl_id) : 0;
       }
     }
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 0565f8cd77..e58a59e872 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -195,7 +195,7 @@ Dictionary nvim_get_hl_by_id(Integer hl_id, Boolean rgb, Error *err)
 Integer nvim_get_hl_id_by_name(String name)
   FUNC_API_SINCE(7)
 {
-  return syn_check_group((const char_u *)name.data, (int)name.size);
+  return syn_check_group(name.data, (int)name.size);
 }
 
 Dictionary nvim__get_hl_defs(Integer ns_id, Error *err)
@@ -227,7 +227,7 @@ Dictionary nvim__get_hl_defs(Integer ns_id, Error *err)
 void nvim_set_hl(Integer ns_id, String name, Dictionary val, Error *err)
   FUNC_API_SINCE(7)
 {
-  int hl_id = syn_check_group( (char_u *)(name.data), (int)name.size);
+  int hl_id = syn_check_group(name.data, (int)name.size);
   int link_id = -1;
 
   HlAttrs attrs = dict2hlattrs(val, true, &link_id, err);
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 6d91632dcd..2617859381 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -2711,21 +2711,21 @@ void buflist_list(exarg_T *eap)
     const bool job_running = buf->terminal && terminal_running(buf->terminal);
 
     // skip unspecified buffers
-    if ((!buf->b_p_bl && !eap->forceit && !strchr((char *)eap->arg, 'u'))
-        || (strchr((char *)eap->arg, 'u') && buf->b_p_bl)
-        || (strchr((char *)eap->arg, '+')
+    if ((!buf->b_p_bl && !eap->forceit && !vim_strchr(eap->arg, 'u'))
+        || (vim_strchr(eap->arg, 'u') && buf->b_p_bl)
+        || (vim_strchr(eap->arg, '+')
             && ((buf->b_flags & BF_READERR) || !bufIsChanged(buf)))
-        || (strchr((char *)eap->arg, 'a')
+        || (vim_strchr(eap->arg, 'a')
             && (buf->b_ml.ml_mfp == NULL || buf->b_nwindows == 0))
-        || (strchr((char *)eap->arg, 'h')
+        || (vim_strchr(eap->arg, 'h')
             && (buf->b_ml.ml_mfp == NULL || buf->b_nwindows != 0))
-        || (strchr((char *)eap->arg, 'R') && (!is_terminal || !job_running))
-        || (strchr((char *)eap->arg, 'F') && (!is_terminal || job_running))
-        || (strchr((char *)eap->arg, '-') && buf->b_p_ma)
-        || (strchr((char *)eap->arg, '=') && !buf->b_p_ro)
-        || (strchr((char *)eap->arg, 'x') && !(buf->b_flags & BF_READERR))
-        || (strchr((char *)eap->arg, '%') && buf != curbuf)
-        || (strchr((char *)eap->arg, '#')
+        || (vim_strchr(eap->arg, 'R') && (!is_terminal || !job_running))
+        || (vim_strchr(eap->arg, 'F') && (!is_terminal || job_running))
+        || (vim_strchr(eap->arg, '-') && buf->b_p_ma)
+        || (vim_strchr(eap->arg, '=') && !buf->b_p_ro)
+        || (vim_strchr(eap->arg, 'x') && !(buf->b_flags & BF_READERR))
+        || (vim_strchr(eap->arg, '%') && buf != curbuf)
+        || (vim_strchr(eap->arg, '#')
             && (buf == curbuf || curwin->w_alt_fnum != buf->b_fnum))) {
       continue;
     }
diff --git a/src/nvim/cursor_shape.c b/src/nvim/cursor_shape.c
index 128bc480da..18cade1052 100644
--- a/src/nvim/cursor_shape.c
+++ b/src/nvim/cursor_shape.c
@@ -230,12 +230,11 @@ char_u *parse_shape_opt(int what)
               slashp = vim_strchr(p, '/');
               if (slashp != NULL && slashp < endp) {
                 // "group/langmap_group"
-                i = syn_check_group(p, (int)(slashp - p));
+                i = syn_check_group((char *)p, (int)(slashp - p));
                 p = slashp + 1;
               }
               if (round == 2) {
-                shape_table[idx].id = syn_check_group(p,
-                                                      (int)(endp - p));
+                shape_table[idx].id = syn_check_group((char *)p, (int)(endp - p));
                 shape_table[idx].id_lm = shape_table[idx].id;
                 if (slashp != NULL && slashp < endp) {
                   shape_table[idx].id = i;
diff --git a/src/nvim/debugger.c b/src/nvim/debugger.c
index 58b1d9ce7f..aeaf2555b1 100644
--- a/src/nvim/debugger.c
+++ b/src/nvim/debugger.c
@@ -390,7 +390,7 @@ static char_u *debug_skipped_name;
 /// Called from do_one_cmd() before executing a command.
 void dbg_check_breakpoint(exarg_T *eap)
 {
-  char_u *p;
+  char *p;
 
   debug_skipped = false;
   if (debug_breakpoint_name != NULL) {
@@ -399,9 +399,9 @@ void dbg_check_breakpoint(exarg_T *eap)
       if (debug_breakpoint_name[0] == K_SPECIAL
           && debug_breakpoint_name[1] == KS_EXTRA
           && debug_breakpoint_name[2] == KE_SNR) {
-        p = (char_u *)"<SNR>";
+        p = "<SNR>";
       } else {
-        p = (char_u *)"";
+        p = "";
       }
       smsg(_("Breakpoint in \"%s%s\" line %" PRId64),
            p,
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 5ac733285d..ea49222a93 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -5123,7 +5123,7 @@ static int ins_complete(int c, bool enable_pum)
                     ))) {
           prefix = (char_u *)"";
         }
-        STRCPY((char *)compl_pattern, prefix);
+        STRCPY(compl_pattern, prefix);
         (void)quote_meta(compl_pattern + STRLEN(prefix),
                          line + compl_col, compl_length);
       } else if (--startcol < 0
@@ -5152,13 +5152,13 @@ static int ins_complete(int c, bool enable_pum)
            * xmalloc(7) is enough  -- Acevedo
            */
           compl_pattern = xmalloc(7);
-          STRCPY((char *)compl_pattern, "\\<");
+          STRCPY(compl_pattern, "\\<");
           (void)quote_meta(compl_pattern + 2, line + compl_col, 1);
-          STRCAT((char *)compl_pattern, "\\k");
+          STRCAT(compl_pattern, "\\k");
         } else {
           compl_pattern = xmalloc(quote_meta(NULL, line + compl_col,
                                              compl_length) + 2);
-          STRCPY((char *)compl_pattern, "\\<");
+          STRCPY(compl_pattern, "\\<");
           (void)quote_meta(compl_pattern + 2, line + compl_col,
                            compl_length);
         }
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index a281c09042..ac659fbda4 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -5899,17 +5899,17 @@ void prepare_assert_error(garray_T *gap)
 
   ga_init(gap, 1, 100);
   if (sourcing_name != NULL) {
-    ga_concat(gap, sourcing_name);
+    ga_concat(gap, (char *)sourcing_name);
     if (sourcing_lnum > 0) {
-      ga_concat(gap, (char_u *)" ");
+      ga_concat(gap, " ");
     }
   }
   if (sourcing_lnum > 0) {
     vim_snprintf(buf, ARRAY_SIZE(buf), "line %" PRId64, (int64_t)sourcing_lnum);
-    ga_concat(gap, (char_u *)buf);
+    ga_concat(gap, buf);
   }
   if (sourcing_name != NULL || sourcing_lnum > 0) {
-    ga_concat(gap, (char_u *)": ");
+    ga_concat(gap, ": ");
   }
 }
 
@@ -5923,27 +5923,27 @@ static void ga_concat_esc(garray_T *gap, const char_u *p, int clen)
   if (clen > 1) {
     memmove(buf, p, clen);
     buf[clen] = NUL;
-    ga_concat(gap, buf);
+    ga_concat(gap, (char *)buf);
   } else {
     switch (*p) {
     case BS:
-      ga_concat(gap, (char_u *)"\\b"); break;
+      ga_concat(gap, "\\b"); break;
     case ESC:
-      ga_concat(gap, (char_u *)"\\e"); break;
+      ga_concat(gap, "\\e"); break;
     case FF:
-      ga_concat(gap, (char_u *)"\\f"); break;
+      ga_concat(gap, "\\f"); break;
     case NL:
-      ga_concat(gap, (char_u *)"\\n"); break;
+      ga_concat(gap, "\\n"); break;
     case TAB:
-      ga_concat(gap, (char_u *)"\\t"); break;
+      ga_concat(gap, "\\t"); break;
     case CAR:
-      ga_concat(gap, (char_u *)"\\r"); break;
+      ga_concat(gap, "\\r"); break;
     case '\\':
-      ga_concat(gap, (char_u *)"\\\\"); break;
+      ga_concat(gap, "\\\\"); break;
     default:
       if (*p < ' ') {
         vim_snprintf((char *)buf, NUMBUFLEN, "\\x%02x", *p);
-        ga_concat(gap, buf);
+        ga_concat(gap, (char *)buf);
       } else {
         ga_append(gap, *p);
       }
@@ -5960,7 +5960,7 @@ static void ga_concat_shorten_esc(garray_T *gap, const char_u *str)
   char_u buf[NUMBUFLEN];
 
   if (str == NULL) {
-    ga_concat(gap, (char_u *)"NULL");
+    ga_concat(gap, "NULL");
     return;
   }
 
@@ -5974,12 +5974,12 @@ static void ga_concat_shorten_esc(garray_T *gap, const char_u *str)
       s += clen;
     }
     if (same_len > 20) {
-      ga_concat(gap, (char_u *)"\\[");
+      ga_concat(gap, "\\[");
       ga_concat_esc(gap, p, clen);
-      ga_concat(gap, (char_u *)" occurs ");
+      ga_concat(gap, " occurs ");
       vim_snprintf((char *)buf, NUMBUFLEN, "%d", same_len);
-      ga_concat(gap, buf);
-      ga_concat(gap, (char_u *)" times]");
+      ga_concat(gap, (char *)buf);
+      ga_concat(gap, " times]");
       p = s - 1;
     } else {
       ga_concat_esc(gap, p, clen);
@@ -5995,17 +5995,17 @@ void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv, char_u *exp_str, typ
 
   if (opt_msg_tv->v_type != VAR_UNKNOWN) {
     tofree = (char_u *)encode_tv2echo(opt_msg_tv, NULL);
-    ga_concat(gap, tofree);
+    ga_concat(gap, (char *)tofree);
     xfree(tofree);
-    ga_concat(gap, (char_u *)": ");
+    ga_concat(gap, ": ");
   }
 
   if (atype == ASSERT_MATCH || atype == ASSERT_NOTMATCH) {
-    ga_concat(gap, (char_u *)"Pattern ");
+    ga_concat(gap, "Pattern ");
   } else if (atype == ASSERT_NOTEQUAL) {
-    ga_concat(gap, (char_u *)"Expected not equal to ");
+    ga_concat(gap, "Expected not equal to ");
   } else {
-    ga_concat(gap, (char_u *)"Expected ");
+    ga_concat(gap, "Expected ");
   }
 
   if (exp_str == NULL) {
@@ -6018,11 +6018,11 @@ void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv, char_u *exp_str, typ
 
   if (atype != ASSERT_NOTEQUAL) {
     if (atype == ASSERT_MATCH) {
-      ga_concat(gap, (char_u *)" does not match ");
+      ga_concat(gap, " does not match ");
     } else if (atype == ASSERT_NOTMATCH) {
-      ga_concat(gap, (char_u *)" does match ");
+      ga_concat(gap, " does match ");
     } else {
-      ga_concat(gap, (char_u *)" but got ");
+      ga_concat(gap, " but got ");
     }
     tofree = (char_u *)encode_tv2string(got_tv, NULL);
     ga_concat_shorten_esc(gap, tofree);
@@ -6126,21 +6126,21 @@ int assert_equalfile(typval_T *argvars)
     prepare_assert_error(&ga);
     if (argvars[2].v_type != VAR_UNKNOWN) {
       char *const tofree = encode_tv2echo(&argvars[2], NULL);
-      ga_concat(&ga, (char_u *)tofree);
+      ga_concat(&ga, tofree);
       xfree(tofree);
-      ga_concat(&ga, (char_u *)": ");
+      ga_concat(&ga, ": ");
     }
-    ga_concat(&ga, IObuff);
+    ga_concat(&ga, (char *)IObuff);
     if (lineidx > 0) {
       line1[lineidx] = NUL;
       line2[lineidx] = NUL;
-      ga_concat(&ga, (char_u *)" after \"");
-      ga_concat(&ga, (char_u *)line1);
+      ga_concat(&ga, " after \"");
+      ga_concat(&ga, line1);
       if (STRCMP(line1, line2) != 0) {
-        ga_concat(&ga, (char_u *)"\" vs \"");
-        ga_concat(&ga, (char_u *)line2);
+        ga_concat(&ga, "\" vs \"");
+        ga_concat(&ga, line2);
       }
-      ga_concat(&ga, (char_u *)"\"");
+      ga_concat(&ga, "\"");
     }
     assert_error(&ga);
     ga_clear(&ga);
@@ -6166,13 +6166,13 @@ int assert_inrange(typval_T *argvars)
       prepare_assert_error(&ga);
       if (argvars[3].v_type != VAR_UNKNOWN) {
         char_u *const tofree = (char_u *)encode_tv2string(&argvars[3], NULL);
-        ga_concat(&ga, tofree);
+        ga_concat(&ga, (char *)tofree);
         xfree(tofree);
       } else {
         char msg[80];
         vim_snprintf(msg, sizeof(msg), "Expected range %g - %g, but got %g",
                      flower, fupper, factual);
-        ga_concat(&ga, (char_u *)msg);
+        ga_concat(&ga, msg);
       }
       assert_error(&ga);
       ga_clear(&ga);
@@ -6238,7 +6238,7 @@ int assert_exception(typval_T *argvars)
   const char *const error = tv_get_string_chk(&argvars[0]);
   if (vimvars[VV_EXCEPTION].vv_str == NULL) {
     prepare_assert_error(&ga);
-    ga_concat(&ga, (char_u *)"v:exception is not set");
+    ga_concat(&ga, "v:exception is not set");
     assert_error(&ga);
     ga_clear(&ga);
     return 1;
@@ -6259,10 +6259,10 @@ static void assert_append_cmd_or_arg(garray_T *gap, typval_T *argvars, const cha
 {
   if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN) {
     char *const tofree = encode_tv2echo(&argvars[2], NULL);
-    ga_concat(gap, (char_u *)tofree);
+    ga_concat(gap, tofree);
     xfree(tofree);
   } else {
-    ga_concat(gap, (char_u *)cmd);
+    ga_concat(gap, cmd);
   }
 }
 
@@ -6280,11 +6280,11 @@ int assert_beeps(typval_T *argvars, bool no_beep)
     garray_T ga;
     prepare_assert_error(&ga);
     if (no_beep) {
-      ga_concat(&ga, (const char_u *)"command did beep: ");
+      ga_concat(&ga, "command did beep: ");
     } else {
-      ga_concat(&ga, (const char_u *)"command did not beep: ");
+      ga_concat(&ga, "command did not beep: ");
     }
-    ga_concat(&ga, (const char_u *)cmd);
+    ga_concat(&ga, cmd);
     assert_error(&ga);
     ga_clear(&ga);
     ret = 1;
@@ -6312,7 +6312,7 @@ int assert_fails(typval_T *argvars)
   do_cmdline_cmd(cmd);
   if (!called_emsg) {
     prepare_assert_error(&ga);
-    ga_concat(&ga, (const char_u *)"command did not fail: ");
+    ga_concat(&ga, "command did not fail: ");
     assert_append_cmd_or_arg(&ga, argvars, cmd);
     assert_error(&ga);
     ga_clear(&ga);
@@ -6326,7 +6326,7 @@ int assert_fails(typval_T *argvars)
       prepare_assert_error(&ga);
       fill_assert_error(&ga, &argvars[2], NULL, &argvars[1],
                         &vimvars[VV_ERRMSG].vv_tv, ASSERT_OTHER);
-      ga_concat(&ga, (char_u *)": ");
+      ga_concat(&ga, ": ");
       assert_append_cmd_or_arg(&ga, argvars, cmd);
       assert_error(&ga);
       ga_clear(&ga);
diff --git a/src/nvim/eval/encode.c b/src/nvim/eval/encode.c
index 5ef0045659..2d4d9fdea9 100644
--- a/src/nvim/eval/encode.c
+++ b/src/nvim/eval/encode.c
@@ -29,7 +29,6 @@
 #include "nvim/message.h"
 #include "nvim/vim.h"  // For _()
 
-#define ga_concat(a, b) ga_concat(a, (char_u *)b)
 #define utf_ptr2char(b) utf_ptr2char((char_u *)b)
 #define utf_ptr2len(b) ((size_t)utf_ptr2len((char_u *)b))
 #define utf_char2len(b) ((size_t)utf_char2len(b))
@@ -142,7 +141,7 @@ static int conv_error(const char *const msg, const MPConvStack *const mpstack,
       char *const key = encode_tv2string(&key_tv, NULL);
       vim_snprintf((char *)IObuff, IOSIZE, key_msg, key);
       xfree(key);
-      ga_concat(&msg_ga, IObuff);
+      ga_concat(&msg_ga, (char *)IObuff);
       break;
     }
     case kMPConvPairs:
@@ -163,7 +162,7 @@ static int conv_error(const char *const msg, const MPConvStack *const mpstack,
           || (TV_LIST_ITEM_TV(li)->v_type != VAR_LIST
               && tv_list_len(TV_LIST_ITEM_TV(li)->vval.v_list) <= 0)) {
         vim_snprintf((char *)IObuff, IOSIZE, idx_msg, idx);
-        ga_concat(&msg_ga, IObuff);
+        ga_concat(&msg_ga, (char *)IObuff);
       } else {
         assert(li != NULL);
         listitem_T *const first_item =
@@ -173,7 +172,7 @@ static int conv_error(const char *const msg, const MPConvStack *const mpstack,
         char *const key = encode_tv2echo(&key_tv, NULL);
         vim_snprintf((char *)IObuff, IOSIZE, key_pair_msg, key, idx);
         xfree(key);
-        ga_concat(&msg_ga, IObuff);
+        ga_concat(&msg_ga, (char *)IObuff);
       }
       break;
     }
@@ -193,7 +192,7 @@ static int conv_error(const char *const msg, const MPConvStack *const mpstack,
     case kMPConvPartialList: {
       const int idx = (int)(v.data.a.arg - v.data.a.argv) - 1;
       vim_snprintf((char *)IObuff, IOSIZE, partial_arg_i_msg, idx);
-      ga_concat(&msg_ga, IObuff);
+      ga_concat(&msg_ga, (char *)IObuff);
       break;
     }
     }
@@ -355,20 +354,20 @@ int encode_read_from_list(ListReaderState *const state, char *const buf, const s
     const float_T flt_ = (flt); \
     switch (xfpclassify(flt_)) { \
     case FP_NAN: { \
-      ga_concat(gap, (char_u *)"str2float('nan')"); \
+      ga_concat(gap, "str2float('nan')"); \
       break; \
     } \
     case FP_INFINITE: { \
       if (flt_ < 0) { \
         ga_append(gap, '-'); \
       } \
-      ga_concat(gap, (char_u *)"str2float('inf')"); \
+      ga_concat(gap, "str2float('inf')"); \
       break; \
     } \
     default: { \
       char numbuf[NUMBUFLEN]; \
       vim_snprintf(numbuf, ARRAY_SIZE(numbuf), "%g", flt_); \
-      ga_concat(gap, (char_u *)numbuf); \
+      ga_concat(gap, numbuf); \
     } \
     } \
   } while (0)
@@ -569,7 +568,7 @@ int encode_read_from_list(ListReaderState *const state, char *const buf, const s
     default: { \
       char numbuf[NUMBUFLEN]; \
       vim_snprintf(numbuf, ARRAY_SIZE(numbuf), "%g", flt_); \
-      ga_concat(gap, (char_u *)numbuf); \
+      ga_concat(gap, numbuf); \
       break; \
     } \
     } \
@@ -874,7 +873,7 @@ char *encode_tv2echo(typval_T *tv, size_t *len)
   ga_init(&ga, (int)sizeof(char), 80);
   if (tv->v_type == VAR_STRING || tv->v_type == VAR_FUNC) {
     if (tv->vval.v_string != NULL) {
-      ga_concat(&ga, tv->vval.v_string);
+      ga_concat(&ga, (char *)tv->vval.v_string);
     }
   } else {
     const int eve_ret = encode_vim_to_echo(&ga, tv, N_(":echo argument"));
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 709ef8e5b6..17cf141b54 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -491,7 +491,7 @@ static void f_assert_report(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   garray_T ga;
 
   prepare_assert_error(&ga);
-  ga_concat(&ga, (const char_u *)tv_get_string(&argvars[0]));
+  ga_concat(&ga, tv_get_string(&argvars[0]));
   assert_error(&ga);
   ga_clear(&ga);
   rettv->vval.v_number = 1;
@@ -5909,7 +5909,7 @@ static void f_list2str(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   TV_LIST_ITER_CONST(l, li, {
     buf[utf_char2bytes(tv_get_number(TV_LIST_ITEM_TV(li)), buf)] = NUL;
-    ga_concat(&ga, buf);
+    ga_concat(&ga, (char *)buf);
   });
   ga_append(&ga, NUL);
 
@@ -12012,10 +12012,10 @@ static void f_winrestcmd(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
       snprintf((char *)buf, sizeof(buf), "%dresize %d|", winnr,
                wp->w_height);
-      ga_concat(&ga, buf);
+      ga_concat(&ga, (char *)buf);
       snprintf((char *)buf, sizeof(buf), "vert %dresize %d|", winnr,
                wp->w_width);
-      ga_concat(&ga, buf);
+      ga_concat(&ga, (char *)buf);
       winnr++;
     }
   }
diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index cfc95ba167..6300ce6150 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -789,12 +789,12 @@ static int list_join_inner(garray_T *const gap, list_T *const l, const char *con
     if (first) {
       first = false;
     } else {
-      ga_concat(gap, (const char_u *)sep);
+      ga_concat(gap, sep);
     }
     const Join *const p = ((const Join *)join_gap->ga_data) + i;
 
     if (p->s != NULL) {
-      ga_concat(gap, p->s);
+      ga_concat(gap, (char *)p->s);
     }
     line_breakcheck();
   }
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 3bfbb42d87..d247118589 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -4409,7 +4409,7 @@ skip:
         pre_src_id = (int)nvim_create_namespace((String)STRING_INIT);
       }
       if (pre_hl_id == 0) {
-        pre_hl_id = syn_check_group((char_u *)S_LEN("Substitute"));
+        pre_hl_id = syn_check_group(S_LEN("Substitute"));
       }
       curbuf->b_changed = save_b_changed;  // preserve 'modified' during preview
       preview_buf = show_sub(eap, old_cursor, &preview_lines,
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 46b86fbc84..c3cde2f15a 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -1984,7 +1984,7 @@ static void cmd_source_buffer(const exarg_T *const eap)
     if (ga.ga_len > 400) {
       ga_set_growsize(&ga, MAX(ga.ga_len, 8000));
     }
-    ga_concat(&ga, ml_get(curr_lnum));
+    ga_concat(&ga, (char *)ml_get(curr_lnum));
     ga_append(&ga, NL);
   }
   ((char_u *)ga.ga_data)[ga.ga_len - 1] = NUL;
@@ -2459,7 +2459,7 @@ char_u *getsourceline(int c, void *cookie, int indent, bool do_concat)
       garray_T ga;
 
       ga_init(&ga, (int)sizeof(char_u), 400);
-      ga_concat(&ga, line);
+      ga_concat(&ga, (char *)line);
       while (sp->nextline != NULL
              && concat_continued_line(&ga, 400, sp->nextline,
                                       STRLEN(sp->nextline))) {
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index f4f07e0680..4c4d3e89e4 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -6595,7 +6595,7 @@ char *script_get(exarg_T *const eap, size_t *const lenp)
     }
 
     if (!eap->skip) {
-      ga_concat(&ga, (const char_u *)theline);
+      ga_concat(&ga, theline);
       ga_append(&ga, '\n');
     }
     xfree(theline);
diff --git a/src/nvim/garray.c b/src/nvim/garray.c
index bc3b7211c9..69ad17ebcb 100644
--- a/src/nvim/garray.c
+++ b/src/nvim/garray.c
@@ -192,13 +192,13 @@ char_u *ga_concat_strings(const garray_T *gap) FUNC_ATTR_NONNULL_RET
 ///
 /// @param gap
 /// @param s
-void ga_concat(garray_T *gap, const char_u *restrict s)
+void ga_concat(garray_T *gap, const char *restrict s)
 {
   if (s == NULL) {
     return;
   }
 
-  ga_concat_len(gap, (const char *restrict)s, strlen((char *)s));
+  ga_concat_len(gap, s, strlen((char *)s));
 }
 
 /// Concatenate a string to a growarray which contains characters
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index a53742b17b..280d2506c6 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -4470,7 +4470,7 @@ static char_u *translate_mapping(char_u *str, int cpo_flags)
         str += 2;
       }
       if (IS_SPECIAL(c) || modifiers) {         // special key
-        ga_concat(&ga, get_special_key_name(c, modifiers));
+        ga_concat(&ga, (char *)get_special_key_name(c, modifiers));
         continue;         // for (str)
       }
     }
@@ -4564,7 +4564,7 @@ char_u *getcmdkeycmd(int promptc, void *cookie, int indent, bool do_concat)
       aborted = true;
     } else if (IS_SPECIAL(c1)) {
       if (c1 == K_SNR) {
-        ga_concat(&line_ga, (char_u *)"<SNR>");
+        ga_concat(&line_ga, "<SNR>");
       } else {
         EMSG2(e_cmdmap_key, get_special_key_name(c1, cmod));
         aborted = true;
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index bb325b3f25..737e668e81 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -306,7 +306,7 @@ void update_window_hl(win_T *wp, bool invalid)
   // syntax group! It needs at least 10 layers of special casing! Noooooo!
   //
   // haha, theme engine go brrr
-  int normality = syn_check_group((const char_u *)S_LEN("Normal"));
+  int normality = syn_check_group(S_LEN("Normal"));
   int ns_attr = ns_get_hl(-1, normality, false, false);
   if (ns_attr > 0) {
     // TODO(bfredl): hantera NormalNC and so on
@@ -890,7 +890,7 @@ HlAttrs dict2hlattrs(Dictionary dict, bool use_rgb, int *link_id, Error *err)
     } else if (link_id && strequal(key, "link")) {
       if (val.type == kObjectTypeString) {
         String str = val.data.string;
-        *link_id = syn_check_group((const char_u *)str.data, (int)str.size);
+        *link_id = syn_check_group(str.data, (int)str.size);
       } else if (val.type == kObjectTypeInteger) {
         // TODO(bfredl): validate range?
         *link_id = (int)val.data.integer;
diff --git a/src/nvim/marktree.c b/src/nvim/marktree.c
index e62f91e698..fd7012e895 100644
--- a/src/nvim/marktree.c
+++ b/src/nvim/marktree.c
@@ -1168,8 +1168,7 @@ char *mt_inspect_rec(MarkTree *b)
 void mt_inspect_node(MarkTree *b, garray_T *ga, mtnode_t *n, mtpos_t off)
 {
   static char buf[1024];
-#define GA_PUT(x) ga_concat(ga, (char_u *)(x))
-  GA_PUT("[");
+  ga_concat(ga, "[");
   if (n->level) {
     mt_inspect_node(b, ga, n->ptr[0], off);
   }
@@ -1177,14 +1176,13 @@ void mt_inspect_node(MarkTree *b, garray_T *ga, mtnode_t *n, mtpos_t off)
     mtpos_t p = n->key[i].pos;
     unrelative(off, &p);
     snprintf((char *)buf, sizeof(buf), "%d/%d", p.row, p.col);
-    GA_PUT(buf);
+    ga_concat(ga, buf);
     if (n->level) {
       mt_inspect_node(b, ga, n->ptr[i+1], p);
     } else {
-      GA_PUT(",");
+      ga_concat(ga, ",");
     }
   }
-  GA_PUT("]");
-#undef GA_PUT
+  ga_concat(ga, "]");
 }
 
diff --git a/src/nvim/message.c b/src/nvim/message.c
index cc4319b8da..c4aab18c35 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -1609,7 +1609,7 @@ char *str2special_save(const char *const str, const bool replace_spaces, const b
 
   const char *p = str;
   while (*p != NUL) {
-    ga_concat(&ga, (const char_u *)str2special(&p, replace_spaces, replace_lt));
+    ga_concat(&ga, str2special(&p, replace_spaces, replace_lt));
   }
   ga_append(&ga, NUL);
   return (char *)ga.ga_data;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index a9bff8285c..b766ae92cf 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -3745,7 +3745,7 @@ static bool parse_winhl_opt(win_T *wp)
     char *hi = colon+1;
     char *commap = xstrchrnul(hi, ',');
     int len = (int)(commap-hi);
-    int hl_id = len ? syn_check_group((char_u *)hi, len) : -1;
+    int hl_id = len ? syn_check_group(hi, len) : -1;
 
     if (strncmp("Normal", p, nlen) == 0) {
       w_hl_id_normal = hl_id;
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index fcd8fb1118..d8cd8c2008 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -2208,7 +2208,7 @@ static int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool noc
 
     if (provider_err) {
       Decoration err_decor = DECORATION_INIT;
-      int hl_err = syn_check_group((char_u *)S_LEN("ErrorMsg"));
+      int hl_err = syn_check_group(S_LEN("ErrorMsg"));
       kv_push(err_decor.virt_text,
               ((VirtTextChunk){ .text = provider_err,
                                 .hl_id = hl_err }));
diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 2610df666b..10f93913ad 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -3978,7 +3978,7 @@ static bool shada_removable(const char *name)
 
   char *new_name = (char *)home_replace_save(NULL, (char_u *)name);
   for (p = (char *)p_shada; *p; ) {
-    (void)(char *)copy_option_part((char_u **)&p, (char_u *)part, ARRAY_SIZE(part), ", ");
+    (void)copy_option_part((char_u **)&p, (char_u *)part, ARRAY_SIZE(part), ", ");
     if (part[0] == 'r') {
       home_replace(NULL, (char_u *)(part + 1), (char_u *)NameBuff, MAXPATHL, true);
       size_t n = STRLEN(NameBuff);
diff --git a/src/nvim/sign.c b/src/nvim/sign.c
index 25427de6bf..1b100161bf 100644
--- a/src/nvim/sign.c
+++ b/src/nvim/sign.c
@@ -902,7 +902,7 @@ static int sign_define_init_text(sign_T *sp, char_u *text)
 
 /// Define a new sign or update an existing sign
 int sign_define_by_name(char_u *name, char_u *icon, char_u *linehl, char_u *text, char_u *texthl,
-                        char_u *numhl)
+                        char *numhl)
 {
   sign_T *sp_prev;
   sign_T *sp;
@@ -940,11 +940,11 @@ int sign_define_by_name(char_u *name, char_u *icon, char_u *linehl, char_u *text
   }
 
   if (linehl != NULL) {
-    sp->sn_line_hl = syn_check_group(linehl, (int)STRLEN(linehl));
+    sp->sn_line_hl = syn_check_group((char *)linehl, (int)STRLEN(linehl));
   }
 
   if (texthl != NULL) {
-    sp->sn_text_hl = syn_check_group(texthl, (int)STRLEN(texthl));
+    sp->sn_text_hl = syn_check_group((char *)texthl, (int)STRLEN(texthl));
   }
 
   if (numhl != NULL) {
@@ -1167,7 +1167,7 @@ static void sign_define_cmd(char_u *sign_name, char_u *cmdline)
   }
 
   if (!failed) {
-    sign_define_by_name(sign_name, icon, linehl, text, texthl, numhl);
+    sign_define_by_name(sign_name, icon, linehl, text, texthl, (char *)numhl);
   }
 
   xfree(icon);
@@ -1871,7 +1871,7 @@ int sign_define_from_dict(const char *name_arg, dict_T *dict)
   }
 
   if (sign_define_by_name((char_u *)name, (char_u *)icon, (char_u *)linehl,
-                          (char_u *)text, (char_u *)texthl, (char_u *)numhl)
+                          (char_u *)text, (char_u *)texthl, numhl)
       == OK) {
     retval = 0;
   }
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index 772275df84..2a501f4714 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -2659,7 +2659,7 @@ static afffile_T *spell_read_aff(spellinfo_T *spin, char_u *fname)
 
           // We simply concatenate all the MAP strings, separated by
           // slashes.
-          ga_concat(&spin->si_map, items[1]);
+          ga_concat(&spin->si_map, (char *)items[1]);
           ga_append(&spin->si_map, '/');
         }
       }
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 49f54dcfe1..2b5faee8de 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -4423,7 +4423,7 @@ static void syn_cmd_keyword(exarg_T *eap, int syncing)
     if (eap->skip) {
       syn_id = -1;
     } else {
-      syn_id = syn_check_group(arg, (int)(group_name_end - arg));
+      syn_id = syn_check_group((char *)arg, (int)(group_name_end - arg));
     }
     if (syn_id != 0) {
       // Allocate a buffer, for removing backslashes in the keyword.
@@ -4560,7 +4560,7 @@ static void syn_cmd_match(exarg_T *eap, int syncing)
     if (!ends_excmd(*rest) || eap->skip) {
       rest = NULL;
     } else {
-      if ((syn_id = syn_check_group(arg, (int)(group_name_end - arg))) != 0) {
+      if ((syn_id = syn_check_group((char *)arg, (int)(group_name_end - arg))) != 0) {
         syn_incl_toplevel(syn_id, &syn_opt_arg.flags);
         /*
          * Store the pattern in the syn_items list
@@ -4709,7 +4709,7 @@ static void syn_cmd_region(exarg_T *eap, int syncing)
       if ((p - rest == 4 && STRNCMP(rest, "NONE", 4) == 0) || eap->skip) {
         matchgroup_id = 0;
       } else {
-        matchgroup_id = syn_check_group(rest, (int)(p - rest));
+        matchgroup_id = syn_check_group((char *)rest, (int)(p - rest));
         if (matchgroup_id == 0) {
           illegal = true;
           break;
@@ -4768,7 +4768,7 @@ static void syn_cmd_region(exarg_T *eap, int syncing)
       rest = NULL;
     } else {
       ga_grow(&(curwin->w_s->b_syn_patterns), pat_count);
-      if ((syn_id = syn_check_group(arg, (int)(group_name_end - arg))) != 0) {
+      if ((syn_id = syn_check_group((char *)arg, (int)(group_name_end - arg))) != 0) {
         syn_incl_toplevel(syn_id, &syn_opt_arg.flags);
         /*
          * Store the start/skip/end in the syn_items list
@@ -5264,8 +5264,7 @@ static void syn_cmd_sync(exarg_T *eap, int syncing)
       if (!ends_excmd(*next_arg)) {
         arg_end = skiptowhite(next_arg);
         if (!eap->skip) {
-          curwin->w_s->b_syn_sync_id = syn_check_group(next_arg,
-                                                       (int)(arg_end - next_arg));
+          curwin->w_s->b_syn_sync_id = syn_check_group((char *)next_arg, (int)(arg_end - next_arg));
         }
         next_arg = skipwhite(arg_end);
       } else if (!eap->skip) {
@@ -5447,7 +5446,7 @@ static int get_id_list(char_u **const arg, const int keylen, int16_t **const lis
          * Handle full group name.
          */
         if (vim_strpbrk(name + 1, (char_u *)"\\.*^$~[") == NULL) {
-          id = syn_check_group(name + 1, (int)(end - p));
+          id = syn_check_group((char *)(name + 1), (int)(end - p));
         } else {
           // Handle match of regexp with group names.
           *name = '^';
@@ -6813,13 +6812,11 @@ void do_highlight(const char *line, const bool forceit, const bool init)
       return;
     }
 
-    from_id = syn_check_group((const char_u *)from_start,
-                              (int)(from_end - from_start));
+    from_id = syn_check_group(from_start, (int)(from_end - from_start));
     if (strncmp(to_start, "NONE", 4) == 0) {
       to_id = 0;
     } else {
-      to_id = syn_check_group((const char_u *)to_start,
-                              (int)(to_end - to_start));
+      to_id = syn_check_group(to_start, (int)(to_end - to_start));
     }
 
     if (from_id > 0) {
@@ -6880,7 +6877,7 @@ void do_highlight(const char *line, const bool forceit, const bool init)
   }
 
   // Find the group name in the table.  If it does not exist yet, add it.
-  id = syn_check_group((const char_u *)line, (int)(name_end - line));
+  id = syn_check_group(line, (int)(name_end - line));
   if (id == 0) {  // Failed (out of memory).
     return;
   }
@@ -7684,11 +7681,11 @@ char_u *syn_id2name(int id)
 /// @param len length of \p pp
 ///
 /// @return 0 for failure else the id of the group
-int syn_check_group(const char_u *name, int len)
+int syn_check_group(const char *name, int len)
 {
-  int id = syn_name2id_len(name, len);
+  int id = syn_name2id_len((char_u *)name, len);
   if (id == 0) {  // doesn't exist yet
-    return syn_add_group(vim_strnsave(name, len));
+    return syn_add_group(vim_strnsave((char_u *)name, len));
   }
   return id;
 }
@@ -7888,7 +7885,7 @@ void highlight_changed(void)
 
   /// Translate builtin highlight groups into attributes for quick lookup.
   for (int hlf = 0; hlf < HLF_COUNT; hlf++) {
-    id = syn_check_group((char_u *)hlf_names[hlf], STRLEN(hlf_names[hlf]));
+    id = syn_check_group(hlf_names[hlf], STRLEN(hlf_names[hlf]));
     if (id == 0) {
       abort();
     }
diff --git a/src/nvim/syntax.h b/src/nvim/syntax.h
index e61c75c840..15fc084a0a 100644
--- a/src/nvim/syntax.h
+++ b/src/nvim/syntax.h
@@ -27,7 +27,7 @@
 #define HL_CONCEAL     0x20000  // can be concealed
 #define HL_CONCEALENDS 0x40000  // can be concealed
 
-#define SYN_GROUP_STATIC(s) syn_check_group((char_u *)S_LEN(s))
+#define SYN_GROUP_STATIC(s) syn_check_group(S_LEN(s))
 
 typedef struct {
   char *name;
diff --git a/src/nvim/ui_compositor.c b/src/nvim/ui_compositor.c
index 7a0f68cfeb..d7becb4fd4 100644
--- a/src/nvim/ui_compositor.c
+++ b/src/nvim/ui_compositor.c
@@ -89,10 +89,10 @@ void ui_comp_init(void)
 
 void ui_comp_syn_init(void)
 {
-  dbghl_normal = syn_check_group((char_u *)S_LEN("RedrawDebugNormal"));
-  dbghl_clear = syn_check_group((char_u *)S_LEN("RedrawDebugClear"));
-  dbghl_composed = syn_check_group((char_u *)S_LEN("RedrawDebugComposed"));
-  dbghl_recompose = syn_check_group((char_u *)S_LEN("RedrawDebugRecompose"));
+  dbghl_normal = syn_check_group(S_LEN("RedrawDebugNormal"));
+  dbghl_clear = syn_check_group(S_LEN("RedrawDebugClear"));
+  dbghl_composed = syn_check_group(S_LEN("RedrawDebugComposed"));
+  dbghl_recompose = syn_check_group(S_LEN("RedrawDebugRecompose"));
 }
 
 void ui_comp_attach(UI *ui)
diff --git a/src/nvim/version.c b/src/nvim/version.c
index bc06ef0b98..9e2358c9a3 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -2017,9 +2017,9 @@ void ex_version(exarg_T *eap)
 /// When "wrap" is TRUE wrap the string in [].
 /// @param s
 /// @param wrap
-static void version_msg_wrap(char_u *s, int wrap)
+static void version_msg_wrap(char *s, int wrap)
 {
-  int len = vim_strsize(s) + (wrap ? 2 : 0);
+  int len = vim_strsize((char_u *)s) + (wrap ? 2 : 0);
 
   if (!got_int
       && (len < Columns)
@@ -2032,7 +2032,7 @@ static void version_msg_wrap(char_u *s, int wrap)
     if (wrap) {
       msg_puts("[");
     }
-    msg_puts((char *)s);
+    msg_puts(s);
     if (wrap) {
       msg_puts("]");
     }
@@ -2041,7 +2041,7 @@ static void version_msg_wrap(char_u *s, int wrap)
 
 static void version_msg(char *s)
 {
-  version_msg_wrap((char_u *)s, false);
+  version_msg_wrap(s, false);
 }
 
 /// List all features.
@@ -2082,7 +2082,7 @@ void list_in_columns(char_u **items, int size, int current)
   if (Columns < width) {
     // Not enough screen columns - show one per line
     for (i = 0; i < item_count; i++) {
-      version_msg_wrap(items[i], i == current);
+      version_msg_wrap((char *)items[i], i == current);
       if (msg_col > 0 && i < item_count - 1) {
         msg_putchar('\n');
       }
diff --git a/src/nvim/window.c b/src/nvim/window.c
index ff97eaa757..1fe4aa1add 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -6693,7 +6693,7 @@ int match_add(win_T *wp, const char *const grp, const char *const pat, int prio,
       cur = cur->next;
     }
   }
-  if ((hlg_id = syn_check_group((const char_u *)grp, strlen(grp))) == 0) {
+  if ((hlg_id = syn_check_group(grp, strlen(grp))) == 0) {
     return -1;
   }
   if (pat != NULL && (regprog = vim_regcomp((char_u *)pat, RE_MAGIC)) == NULL) {