new file mode 100644
--- /dev/null
+++ b/src/vim9script.c
@@ -0,0 +1,405 @@
+/* vi:set ts=8 sts=4 sw=4 noet:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * vim9script.c: :vim9script, :import, :export and friends
+ */
+
+#include "vim.h"
+
+#if defined(FEAT_EVAL) || defined(PROTO)
+
+#include "vim9.h"
+
+static char e_needs_vim9[] = N_("E1042: import/export can only be used in vim9script");
+
+    int
+in_vim9script(void)
+{
+    // TODO: go up the stack?
+    return current_sctx.sc_version == SCRIPT_VERSION_VIM9;
+}
+
+/*
+ * ":vim9script".
+ */
+    void
+ex_vim9script(exarg_T *eap)
+{
+    scriptitem_T *si = &SCRIPT_ITEM(current_sctx.sc_sid);
+
+    if (!getline_equal(eap->getline, eap->cookie, getsourceline))
+    {
+	emsg(_("E1038: vim9script can only be used in a script"));
+	return;
+    }
+    if (si->sn_had_command)
+    {
+	emsg(_("E1039: vim9script must be the first command in a script"));
+	return;
+    }
+    current_sctx.sc_version = SCRIPT_VERSION_VIM9;
+    si->sn_version = SCRIPT_VERSION_VIM9;
+    si->sn_had_command = TRUE;
+
+    if (STRCMP(p_cpo, CPO_VIM) != 0)
+    {
+	si->sn_save_cpo = p_cpo;
+	p_cpo = vim_strsave((char_u *)CPO_VIM);
+    }
+}
+
+/*
+ * ":export let Name: type"
+ * ":export const Name: type"
+ * ":export def Name(..."
+ * ":export class Name ..."
+ *
+ * ":export {Name, ...}"
+ */
+    void
+ex_export(exarg_T *eap UNUSED)
+{
+    if (current_sctx.sc_version != SCRIPT_VERSION_VIM9)
+    {
+	emsg(_(e_needs_vim9));
+	return;
+    }
+
+    eap->cmd = eap->arg;
+    (void)find_ex_command(eap, NULL, lookup_scriptvar, NULL);
+    switch (eap->cmdidx)
+    {
+	case CMD_let:
+	case CMD_const:
+	case CMD_def:
+	// case CMD_class:
+	    is_export = TRUE;
+	    do_cmdline(eap->cmd, eap->getline, eap->cookie,
+						DOCMD_VERBOSE + DOCMD_NOWAIT);
+
+	    // The command will reset "is_export" when exporting an item.
+	    if (is_export)
+	    {
+		emsg(_("E1044: export with invalid argument"));
+		is_export = FALSE;
+	    }
+	    break;
+	default:
+	    emsg(_("E1043: Invalid command after :export"));
+	    break;
+    }
+}
+
+/*
+ * Add a new imported item entry to the current script.
+ */
+    static imported_T *
+new_imported(garray_T *gap)
+{
+    if (ga_grow(gap, 1) == OK)
+	return ((imported_T *)gap->ga_data + gap->ga_len++);
+    return NULL;
+}
+
+/*
+ * Free all imported items in script "sid".
+ */
+    void
+free_imports(int sid)
+{
+    scriptitem_T    *si = &SCRIPT_ITEM(sid);
+    int		    idx;
+
+    for (idx = 0; idx < si->sn_imports.ga_len; ++idx)
+    {
+	imported_T *imp = ((imported_T *)si->sn_imports.ga_data + idx);
+
+	vim_free(imp->imp_name);
+    }
+    ga_clear(&si->sn_imports);
+}
+
+/*
+ * ":import Item from 'filename'"
+ * ":import Item as Alias from 'filename'"
+ * ":import {Item} from 'filename'".
+ * ":import {Item as Alias} from 'filename'"
+ * ":import {Item, Item} from 'filename'"
+ * ":import {Item, Item as Alias} from 'filename'"
+ *
+ * ":import * as Name from 'filename'"
+ */
+    void
+ex_import(exarg_T *eap)
+{
+    if (current_sctx.sc_version != SCRIPT_VERSION_VIM9)
+	emsg(_(e_needs_vim9));
+    else
+    {
+	char_u *cmd_end = handle_import(eap->arg, NULL, current_sctx.sc_sid);
+
+	if (cmd_end != NULL)
+	    eap->nextcmd = check_nextcmd(cmd_end);
+    }
+}
+
+/*
+ * Handle an ":import" command and add the resulting imported_T to "gap", when
+ * not NULL, or script "import_sid" sn_imports.
+ * Returns a pointer to after the command or NULL in case of failure
+ */
+    char_u *
+handle_import(char_u *arg_start, garray_T *gap, int import_sid)
+{
+    char_u	*arg = arg_start;
+    char_u	*cmd_end;
+    char_u	*as_ptr = NULL;
+    char_u	*from_ptr;
+    int		as_len = 0;
+    int		ret = FAIL;
+    typval_T	tv;
+    int		sid = -1;
+    int		res;
+
+    if (*arg == '{')
+    {
+	// skip over {item} list
+	while (*arg != NUL && *arg != '}')
+	    ++arg;
+	if (*arg == '}')
+	    arg = skipwhite(arg + 1);
+    }
+    else
+    {
+	if (*arg == '*')
+	    arg = skipwhite(arg + 1);
+	else
+	{
+	    while (eval_isnamec1(*arg))
+		++arg;
+	    arg = skipwhite(arg);
+	}
+	if (STRNCMP("as", arg, 2) == 0 && VIM_ISWHITE(arg[2]))
+	{
+	    // skip over "as Name "
+	    arg = skipwhite(arg + 2);
+	    as_ptr = arg;
+	    while (eval_isnamec1(*arg))
+		++arg;
+	    as_len = (int)(arg - as_ptr);
+	    arg = skipwhite(arg);
+	}
+	else if (*arg_start == '*')
+	{
+	    emsg(_("E1045: Missing \"as\" after *"));
+	    return NULL;
+	}
+    }
+    if (STRNCMP("from", arg, 4) != 0 || !VIM_ISWHITE(arg[4]))
+    {
+	emsg(_("E1045: Missing \"from\""));
+	return NULL;
+    }
+    from_ptr = arg;
+    arg = skipwhite(arg + 4);
+    tv.v_type = VAR_UNKNOWN;
+    // TODO: should we accept any expression?
+    if (*arg == '\'')
+	ret = get_lit_string_tv(&arg, &tv, TRUE);
+    else if (*arg == '"')
+	ret = get_string_tv(&arg, &tv, TRUE);
+    if (ret == FAIL || tv.vval.v_string == NULL || *tv.vval.v_string == NUL)
+    {
+	emsg(_("E1045: Invalid string after \"from\""));
+	return NULL;
+    }
+    cmd_end = arg;
+
+    // find script tv.vval.v_string
+    if (*tv.vval.v_string == '.')
+    {
+	size_t		len;
+	scriptitem_T	*si = &SCRIPT_ITEM(current_sctx.sc_sid);
+	char_u		*tail = gettail(si->sn_name);
+	char_u		*from_name;
+
+	// Relative to current script: "./name.vim", "../../name.vim".
+	len = STRLEN(si->sn_name) - STRLEN(tail) + STRLEN(tv.vval.v_string) + 2;
+	from_name = alloc((int)len);
+	if (from_name == NULL)
+	{
+	    clear_tv(&tv);
+	    return NULL;
+	}
+	vim_strncpy(from_name, si->sn_name, tail - si->sn_name);
+	add_pathsep(from_name);
+	STRCAT(from_name, tv.vval.v_string);
+	simplify_filename(from_name);
+
+	res = do_source(from_name, FALSE, DOSO_NONE, &sid);
+	vim_free(from_name);
+    }
+    else if (mch_isFullName(tv.vval.v_string))
+    {
+	// Absolute path: "/tmp/name.vim"
+	res = do_source(tv.vval.v_string, FALSE, DOSO_NONE, &sid);
+    }
+    else
+    {
+	size_t	    len = 7 + STRLEN(tv.vval.v_string) + 1;
+	char_u	    *from_name;
+
+	// Find file in "import" subdirs in 'runtimepath'.
+	from_name = alloc((int)len);
+	if (from_name == NULL)
+	{
+	    clear_tv(&tv);
+	    return NULL;
+	}
+	vim_snprintf((char *)from_name, len, "import/%s", tv.vval.v_string);
+	res = source_in_path(p_rtp, from_name, DIP_NOAFTER, &sid);
+	vim_free(from_name);
+    }
+
+    if (res == FAIL || sid <= 0)
+    {
+	semsg(_("E1053: Could not import \"%s\""), tv.vval.v_string);
+	clear_tv(&tv);
+	return NULL;
+    }
+    clear_tv(&tv);
+
+    if (*arg_start == '*')
+    {
+	imported_T *imported = new_imported(gap != NULL ? gap
+					: &SCRIPT_ITEM(import_sid).sn_imports);
+
+	if (imported == NULL)
+	    return NULL;
+	imported->imp_name = vim_strnsave(as_ptr, as_len);
+	imported->imp_sid = sid;
+	imported->imp_all = TRUE;
+    }
+    else
+    {
+	scriptitem_T *script = &SCRIPT_ITEM(sid);
+
+	arg = arg_start;
+	if (*arg == '{')
+	    arg = skipwhite(arg + 1);
+	for (;;)
+	{
+	    char_u	*name = arg;
+	    int		name_len;
+	    int		cc;
+	    int		idx;
+	    svar_T	*sv;
+	    imported_T	*imported;
+	    ufunc_T	*ufunc;
+
+	    // isolate one name
+	    while (eval_isnamec1(*arg))
+		++arg;
+	    name_len = (int)(arg - name);
+
+	    // find name in "script"
+	    // TODO: also find script-local user function
+	    cc = *arg;
+	    *arg = NUL;
+	    idx = get_script_item_idx(sid, name, FALSE);
+	    if (idx >= 0)
+	    {
+		sv = ((svar_T *)script->sn_var_vals.ga_data) + idx;
+		if (!sv->sv_export)
+		{
+		    semsg(_("E1049: Item not exported in script: %s"), name);
+		    *arg = cc;
+		    return NULL;
+		}
+	    }
+	    else
+	    {
+		char_u	buffer[200];
+		char_u	*funcname;
+
+		// it could be a user function.
+		if (STRLEN(name) < sizeof(buffer) - 10)
+		    funcname = buffer;
+		else
+		{
+		    funcname = alloc(STRLEN(name) + 10);
+		    if (funcname == NULL)
+		    {
+			*arg = cc;
+			return NULL;
+		    }
+		}
+		funcname[0] = K_SPECIAL;
+		funcname[1] = KS_EXTRA;
+		funcname[2] = (int)KE_SNR;
+		sprintf((char *)funcname + 3, "%ld_%s", (long)sid, name);
+		ufunc = find_func(funcname, NULL);
+		if (funcname != buffer)
+		    vim_free(funcname);
+
+		if (ufunc == NULL)
+		{
+		    semsg(_("E1048: Item not found in script: %s"), name);
+		    *arg = cc;
+		    return NULL;
+		}
+	    }
+
+	    imported = new_imported(gap != NULL ? gap
+					: &SCRIPT_ITEM(import_sid).sn_imports);
+	    if (imported == NULL)
+		return NULL;
+
+	    *arg = cc;
+	    arg = skipwhite(arg);
+
+	    // TODO: check for "as" following
+	    // imported->imp_name = vim_strnsave(as_ptr, as_len);
+	    imported->imp_name = vim_strnsave(name, name_len);
+	    imported->imp_sid = sid;
+	    if (idx >= 0)
+	    {
+		imported->imp_type = sv->sv_type;
+		imported->imp_var_vals_idx = idx;
+	    }
+	    else
+		imported->imp_funcname = ufunc->uf_name;
+
+	    arg = skipwhite(arg);
+	    if (*arg_start != '{')
+		break;
+	    if (*arg == '}')
+	    {
+		arg = skipwhite(arg + 1);
+		break;
+	    }
+
+	    if (*arg != ',')
+	    {
+		emsg(_("E1046: Missing comma in import"));
+		return NULL;
+	    }
+	    arg = skipwhite(arg + 1);
+	}
+	if (arg != from_ptr)
+	{
+	    emsg(_("E1047: syntax error in import"));
+	    return NULL;
+	}
+    }
+    return cmd_end;
+}
+
+#endif // FEAT_EVAL