patch 9.2.1140: Vim9: :def in legacy script can create a script variable

Problem:  A :def function in a legacy script can create a script-local
          variable by assigning to it, while declaring one with "var"
          gives E1101.
Solution: Give E1089 for assigning to an unknown script-local variable
          in any :def function, not only in one defined in a Vim9
          script.  Remove uf_script_ctx_version, which was only used
          for this check.  Do not give it with ":source ++dryrun".

runtime/menu.vim created s:bmenu_short, s:bmenu_count, s:suglist,
s:fromword, s:changeitem, s:additem and s:ignoreitem this way, define
them at the script level.

":source ++dryrun" does not execute ":let" in a legacy script, thus
every script variable would be unknown when compiling.  Document that
reading or calling such a variable without "s:" still gives an error,
and separate the paragraphs of ":source-dryrun" with blank lines.

Test_unlet() created s:somevar this way, define it at the script level
instead.  Test_using_s_var_in_function() checks that assigning to
s:scriptlevel in a :def function of a legacy script gives E1089 when
the variable does not exist.  Test_source_dryrun() checks that
assigning to a script variable with "s:" in a :def function of a
legacy script gives no error with ":source ++dryrun".

closes: #21379

Assisted-by: Claude
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/repeat.txt

@@ -1,4 +1,4 @@
-*repeat.txt*	For Vim version 9.2.  Last change: 2026 Sep 25
+*repeat.txt*	For Vim version 9.2.  Last change: 2026 Sep 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -248,6 +248,7 @@ For writing a Vim script, see chapter 41 of the user manual |usr_41.txt|.
 			Read the script without running it: only what defines
 			something is executed, then every |:def| function in
 			it is compiled and the errors are reported as usual.
+
 			What is executed: `vim9script`, `import`, `def`,
 			`function`, `class`, `interface`, `enum`, `type` and a
 			declaration with `var`, `const` or `final`.  The
@@ -256,17 +257,27 @@ For writing a Vim script, see chapter 41 of the user manual |usr_41.txt|.
 			expression is not evaluated.  A static class variable
 			is treated the same way and an enum value is not
 			created.
+
 			Everything else is skipped, also `finish` and the
 			condition of an `if`, `while` or `for`; a definition
 			inside such a block is executed whether the condition
 			holds or not.  A function may therefore be defined
 			twice, the last definition counts.
+
+			In a legacy script `let` is not executed, thus a
+			script variable created by it does not exist.  A
+			|:def| function can use it with "s:", but reading it
+			or calling it without "s:" gives an error.  Defining a
+			function in a Dictionary it holds, such as
+			`function s:obj.Method()`, fails as well.
+
 			A script that is imported is read the same way, but an
 			autoload script is not loaded.  No |SourceCmd|,
 			|SourcePre| or |SourcePost| autocommand is triggered.
 			A class or enum in an autoload script is defined again
 			by a dry run, and after one by a normal load, since no
 			object was made from it; see |vim9-reload|.
+
 			Note: An error in a definition does not stop the
 			reading, the rest of the script is read as well.  And
 			an error in a line of a function does not stop

runtime/doc/version9.txt

@@ -1,4 +1,4 @@
-*version9.txt*	For Vim version 9.2.  Last change: 2026 Sep 25
+*version9.txt*	For Vim version 9.2.  Last change: 2026 Sep 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -52719,6 +52719,8 @@ Changed ~
 - The highlighting groups |hl-CursorLineFold| and |hl-CursorLineSign| are
   always used when 'cursorline' is set.
 - Virtual text above a line is now counted by |screenpos()| and |virtcol()|.
+- A |:def| function in a legacy script can no longer create a script-local
+  variable by assigning to it, this gives |E1089|.
 
 							*added-9.3*
 Added ~

runtime/doc/vim9.txt

@@ -1,4 +1,4 @@
-*vim9.txt*	For Vim version 9.2.  Last change: 2026 Sep 25
+*vim9.txt*	For Vim version 9.2.  Last change: 2026 Sep 28
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -3610,7 +3610,9 @@ or within a `:function`.  The three rules are:
     regardless of the function's parent context.  Similarly, it gives E1268 in
     the script-local scope of a Vim9 script.
  3. In a legacy Vim script, "s:" is optional in a `:def` function, regardless
-    of the function's parent context.
+    of the function's parent context.  A `:def` function cannot create a
+    script-local variable, assigning to one that does not exist when the
+    function is compiled gives |E1089|.
 
 The following three scripts demonstrate these rules:
 >vim

runtime/menu.vim

@@ -2,7 +2,7 @@
 " You can also use this as a start for your own set of menus.
 "
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2026 Jan 19
+" Last Change:	2026 Sep 28
 " Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 " Note that ":an" (short for ":anoremenu") is often used to make a menu work
@@ -677,6 +677,8 @@ if !exists("no_buffers_menu")
 " wait with building the menu until after loading 'session' files. Makes
 " startup faster.
 let s:bmenu_wait = 1
+let s:bmenu_short = 1
+let s:bmenu_count = 0
 
 " Dictionary of buffer number to name. This helps prevent problems where a
 " buffer as renamed and we didn't keep track of that.
@@ -1008,6 +1010,12 @@ cnoremenu <script> <silent> 1.100 PopUp.Select\ &All	<C-U>call <SID>SelectAll()<
 if has("spell")
   " Spell suggestions in the popup menu.  Note that this will slow down the
   " appearance of the menu!
+  let s:suglist = []
+  let s:fromword = ''
+  let s:changeitem = ''
+  let s:additem = ''
+  let s:ignoreitem = ''
+
   def s:SpellPopup()
     if exists("s:changeitem") && s:changeitem != ''
       call s:SpellDel()

src/structs.h

@@ -2083,7 +2083,6 @@ struct ufunc_S
     sctx_T	uf_script_ctx;	// SCTX where function was defined,
 				// used for s: variables; sc_version changed
 				// for :function
-    int		uf_script_ctx_version;  // original sc_version of SCTX
     int		uf_refcount;	// reference count, see func_name_refcount()
 
     funccall_T	*uf_scoped;	// l: local variables for closure

src/testdir/test_source.vim

@@ -859,6 +859,19 @@ func Test_source_dryrun()
   call assert_true(exists('*DryrunLegacy'))
   delfunc DryrunLegacy
 
+  " a :def function in a legacy script can assign to a script variable
+  " with "s:", although the ":let" that creates it is not executed
+  let lines =<< trim END
+    let s:count = 0
+    def DryrunLegacyDef()
+      s:count += 1
+    enddef
+  END
+  call writefile(lines, 'Xdryrun_legacydef.vim', 'D')
+  source ++dryrun Xdryrun_legacydef.vim
+  call assert_true(exists('*DryrunLegacyDef'))
+  delfunc DryrunLegacyDef
+
   " no SourceCmd, SourcePre or SourcePost autocommand, also not for the
   " imported script
   let g:dryrun_events = ''

src/testdir/test_vim9_assign.vim

@@ -2682,6 +2682,8 @@ def Test_cannot_use_let()
   v9.CheckDefAndScriptFailure(['let a = 34'], 'E1126:', 1)
 enddef
 
+let s:somevar = ''
+
 def Test_unlet()
   g:somevar = 'yes'
   assert_true(exists('g:somevar'))
@@ -3141,6 +3143,15 @@ def Test_using_s_var_in_function()
       call assert_equal(456, s:scriptlevel)
   END
   v9.CheckScriptSuccess(lines)
+
+  # but a :def function cannot create one
+  lines =<< trim END
+      def s:SomeFunc()
+        s:scriptlevel = 456
+      enddef
+      call s:SomeFunc()
+  END
+  v9.CheckScriptFailure(lines, 'E1089: Unknown variable: s:scriptlevel', 1)
 enddef
 
 " Test for specifying a type in assignment

src/userfunc.c

@@ -1624,7 +1624,6 @@ lambda_function_body(
     if (!ASCII_ISUPPER(*ufunc->uf_name))
 	ufunc->uf_flags |= FC_VIM9;
     ufunc->uf_script_ctx = current_sctx;
-    ufunc->uf_script_ctx_version = current_sctx.sc_version;
     ufunc->uf_script_ctx.sc_lnum += sourcing_lnum_top;
     set_function_type(ufunc);
 
@@ -5739,7 +5738,6 @@ define_function(
     fp->uf_calls = 0;
     fp->uf_cleared = FALSE;
     fp->uf_script_ctx = current_sctx;
-    fp->uf_script_ctx_version = current_sctx.sc_version;
     fp->uf_script_ctx.sc_lnum += sourcing_lnum_top;
     if (is_export)
     {

src/version.c

@@ -763,6 +763,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1140,
 /**/
     1139,
 /**/

src/vim9compile.c

@@ -1905,9 +1905,9 @@ compile_lhs_script_var(
 			lhs->lhs_name);
 	    return FAIL;
 	}
-	else if (cctx->ctx_ufunc->uf_script_ctx_version == SCRIPT_VERSION_VIM9
-		&& script_namespace
-		&& !script_var && import == NULL)
+	// With ":source ++dryrun" the ":let" that creates it was not executed.
+	else if (script_namespace && !script_var && import == NULL
+							       && !source_dryrun)
 	{
 	    semsg(_(e_unknown_variable_str), lhs->lhs_name);
 	    return FAIL;