patch 8.2.2760: Vim9: no error for changing a for loop variablev8.2.2760

Problem:    Vim9: no error for changing a for loop variable.
Solution:   Make the loop variable read-only. (issue #8102)

6 files changed, 41 insertions, 12 deletions

diff --git a/src/eval.c b/src/eval.c
index 2e2ca23b6..99768ee28 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1351,7 +1351,8 @@ set_var_lval(
 	{
 	    typval_T tv;
 
-	    if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	    if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	    {
 		emsg(_(e_cannot_mod));
 		*endp = cc;
@@ -1390,7 +1391,8 @@ set_var_lval(
 	listitem_T *ll_li = lp->ll_li;
 	int	    ll_n1 = lp->ll_n1;
 
-	if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	{
 	    emsg(_("E996: Cannot lock a range"));
 	    return;
@@ -1449,7 +1451,8 @@ set_var_lval(
 	/*
 	 * Assign to a List or Dictionary item.
 	 */
-	if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	{
 	    emsg(_("E996: Cannot lock a list or dict"));
 	    return;
@@ -1775,7 +1778,9 @@ next_for_item(void *fi_void, char_u *arg)
 {
     forinfo_T	*fi = (forinfo_T *)fi_void;
     int		result;
-    int		flag = in_vim9script() ? ASSIGN_DECL : 0;
+    int		flag = ASSIGN_FOR_LOOP | (in_vim9script()
+			 ? (ASSIGN_FINAL | ASSIGN_DECL | ASSIGN_NO_MEMBER_TYPE)
+			 : 0);
     listitem_T	*item;
 
     if (fi->fi_blob != NULL)
diff --git a/src/evalvars.c b/src/evalvars.c
index b8a4352f8..eb9ad6da1 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -1315,7 +1315,8 @@ ex_let_one(
     // ":let $VAR = expr": Set environment variable.
     if (*arg == '$')
     {
-	if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	{
 	    emsg(_("E996: Cannot lock an environment variable"));
 	    return NULL;
@@ -1365,9 +1366,11 @@ ex_let_one(
     // ":let &option = expr": Set option value.
     // ":let &l:option = expr": Set local option value.
     // ":let &g:option = expr": Set global option value.
+    // ":for &ts in range(8)": Set option value for for loop
     else if (*arg == '&')
     {
-	if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	{
 	    emsg(_(e_const_option));
 	    return NULL;
@@ -1466,7 +1469,8 @@ ex_let_one(
     // ":let @r = expr": Set register contents.
     else if (*arg == '@')
     {
-	if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	{
 	    emsg(_("E996: Cannot lock a register"));
 	    return NULL;
@@ -3158,7 +3162,7 @@ set_var_const(
     type_T	*type,
     typval_T	*tv_arg,
     int		copy,	    // make copy of value in "tv"
-    int		flags,	    // ASSIGN_CONST, ASSIGN_FINAL, etc.
+    int		flags_arg,  // ASSIGN_CONST, ASSIGN_FINAL, etc.
     int		var_idx)    // index for ":let [a, b] = list"
 {
     typval_T	*tv = tv_arg;
@@ -3169,6 +3173,7 @@ set_var_const(
     int		is_script_local;
     int		vim9script = in_vim9script();
     int		var_in_vim9script;
+    int		flags = flags_arg;
 
     ht = find_var_ht(name, &varname);
     if (ht == NULL || *varname == NUL)
@@ -3187,6 +3192,11 @@ set_var_const(
 	vim9_declare_error(name);
 	goto failed;
     }
+    if ((flags & ASSIGN_FOR_LOOP) && name[1] == ':'
+			      && vim_strchr((char_u *)"gwbt", name[0]) != NULL)
+	// Do not make g:var, w:var, b:var or t:var final.
+	flags &= ~ASSIGN_FINAL;
+
     var_in_vim9script = is_script_local && current_script_is_vim9();
     if (var_in_vim9script && name[0] == '_' && name[1] == NUL)
     {
@@ -3220,7 +3230,8 @@ set_var_const(
 	// Item already exists.  Allowed to replace when reloading.
 	if ((di->di_flags & DI_FLAGS_RELOAD) == 0)
 	{
-	    if (flags & (ASSIGN_CONST | ASSIGN_FINAL))
+	    if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
+					     && (flags & ASSIGN_FOR_LOOP) == 0)
 	    {
 		emsg(_(e_cannot_mod));
 		goto failed;
@@ -3255,7 +3266,8 @@ set_var_const(
 	    // A Vim9 script-local variable is also present in sn_all_vars and
 	    // sn_var_vals.  It may set "type" from "tv".
 	    if (var_in_vim9script)
-		update_vim9_script_var(FALSE, di, flags, tv, &type);
+		update_vim9_script_var(FALSE, di, flags, tv, &type,
+					 (flags & ASSIGN_NO_MEMBER_TYPE) == 0);
 	}
 
 	// existing variable, need to clear the value
@@ -3353,7 +3365,8 @@ set_var_const(
 	// A Vim9 script-local variable is also added to sn_all_vars and
 	// sn_var_vals. It may set "type" from "tv".
 	if (var_in_vim9script)
-	    update_vim9_script_var(TRUE, di, flags, tv, &type);
+	    update_vim9_script_var(TRUE, di, flags, tv, &type,
+					 (flags & ASSIGN_NO_MEMBER_TYPE) == 0);
     }
 
     if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index db1707ace..af7e5fdbb 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2393,6 +2393,14 @@ def Test_for_loop_fails()
   g:adict = {a: 1}
   CheckDefExecFailure(['for i in g:adict', 'echo 3', 'endfor'], 'E1177: For loop on dict not supported')
   unlet g:adict
+
+  var lines =<< trim END
+      var d: list<dict<any>> = [{a: 0}]
+      for e in d
+        e = {a: 0, b: ''}
+      endfor
+  END
+  CheckDefAndScriptFailure2(lines, 'E1018:', 'E46:', 3)
 enddef
 
 def Test_for_loop_script_var()
diff --git a/src/version.c b/src/version.c
index fdb8d0a9b..4861ba1a9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2760,
+/**/
     2759,
 /**/
     2758,
diff --git a/src/vim.h b/src/vim.h
index baa3526d0..4c9e095a1 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2158,6 +2158,7 @@ typedef enum {
 #define ASSIGN_DECL	0x08  // may declare variable if it does not exist
 #define ASSIGN_UNPACK	0x10  // using [a, b] = list
 #define ASSIGN_NO_MEMBER_TYPE 0x20 // use "any" for list and dict member type
+#define ASSIGN_FOR_LOOP 0x40 // assigning to loop variable
 
 #include "ex_cmds.h"	    // Ex command defines
 #include "spell.h"	    // spell checking stuff
diff --git a/src/vim9compile.c b/src/vim9compile.c
index bcba1e322..4a55f1973 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -7590,7 +7590,7 @@ compile_for(char_u *arg_start, cctx_T *cctx)
 
 	    // Reserve a variable to store "var".
 	    // TODO: check for type
-	    var_lvar = reserve_local(cctx, arg, varlen, FALSE, &t_any);
+	    var_lvar = reserve_local(cctx, arg, varlen, TRUE, &t_any);
 	    if (var_lvar == NULL)
 		// out of memory or used as an argument
 		goto failed;