patch 9.2.0301: Vim9: void function return value inconsistent

Problem:  Vim9: void function return value inconsistent between
          script and :def
Solution: Make void built-in functions like bufload() return void
          consistently (Hirohito Higashi)

In Vim9 script, calling a void built-in function (e.g. bufload()) at the
script level did not set rettv to VAR_VOID, making it appear to return
0. Inside :def it correctly returned VAR_VOID and raised E1031.  Set
rettv to VAR_VOID after calling a ret_void built-in function in Vim9
script so the behavior is consistent.

Also fix the documentation for bufload() and ch_logfile() to correctly
state that the return type is void.

closes: #19919

Signed-off-by: Hirohito Higashi <[email protected]>
Signed-off-by: Yegappan Lakshmanan <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: h-east

runtime/doc/builtin.txt

@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.2.  Last change: 2026 Mar 25
+*builtin.txt*	For Vim version 9.2.  Last change: 2026 Apr 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -82,7 +82,7 @@ browsedir({title}, {initdir})	String	put up a directory requester
 bufadd({name})			Number	add a buffer to the buffer list
 bufexists({buf})		Number	|TRUE| if buffer {buf} exists
 buflisted({buf})		Number	|TRUE| if buffer {buf} is listed
-bufload({buf})			Number	load buffer {buf} if not loaded yet
+bufload({buf})			none	load buffer {buf} if not loaded yet
 bufloaded({buf})		Number	|TRUE| if buffer {buf} is loaded
 bufname([{buf}])		String	name of the buffer {buf}
 bufnr([{buf} [, {create}]])	Number	number of the buffer {buf}
@@ -1500,7 +1500,7 @@ bufload({buf})						*bufload()*
 		Can also be used as a |method|: >
 			eval 'somename'->bufload()
 <
-		Return type: |Number|
+		Return type: void
 
 
 bufloaded({buf})					*bufloaded()*

runtime/doc/channel.txt

@@ -1,4 +1,4 @@
-*channel.txt*	For Vim version 9.2.  Last change: 2026 Mar 13
+*channel.txt*	For Vim version 9.2.  Last change: 2026 Apr 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -736,7 +736,7 @@ ch_logfile({fname} [, {mode}])					*ch_logfile()*
 		Can also be used as a |method|: >
 			'logfile'->ch_logfile('w')
 <
-		Return type: |Number|
+		Return type: void
 
 ch_open({address} [, {options}])				*ch_open()*
 		Open a channel to {address}.  See |channel|.

src/evalfunc.c

@@ -3499,6 +3499,8 @@ call_internal_func(
 	return FCERR_OTHER;
     argvars[argcount].v_type = VAR_UNKNOWN;
     global_functions[i].f_func(argvars, rettv);
+    if (in_vim9script() && global_functions[i].f_retfunc == ret_void)
+	rettv->v_type = VAR_VOID;
     return FCERR_NONE;
 }
 
@@ -3509,6 +3511,8 @@ call_internal_func_by_idx(
 	typval_T    *rettv)
 {
     global_functions[idx].f_func(argvars, rettv);
+    if (in_vim9script() && global_functions[idx].f_retfunc == ret_void)
+	rettv->v_type = VAR_VOID;
 }
 
 /*

src/testdir/test_vim9_builtin.vim

@@ -4089,8 +4089,8 @@ enddef
 
 def Test_setenv()
   v9.CheckSourceDefAndScriptFailure(['setenv(1, 2)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1174: String required for argument 1'])
-  assert_equal(0, setenv('', ''))
-  assert_equal(0, setenv('', v:null))
+  setenv('', '')
+  setenv('', v:null)
 enddef
 
 def Test_setfperm()
@@ -4939,7 +4939,7 @@ enddef
 
 def Test_timer_stop()
   v9.CheckSourceDefAndScriptFailure(['timer_stop("x")'], ['E1013: Argument 1: type mismatch, expected number but got string', 'E1210: Number required for argument 1'])
-  assert_equal(0, timer_stop(100))
+  timer_stop(100)
 enddef
 
 def Test_tolower()

src/testdir/test_vim9_func.vim

@@ -5002,6 +5002,41 @@ def Test_void_method_chain()
     defcompile TestFunc
   END
   v9.CheckScriptFailure(lines, 'E1031: Cannot use void value')
+
+  #### Case 4: Script-level and :def should behave the same ####
+  # script-level: void built-in assigned to variable
+  lines =<< trim END
+    vim9script
+    var x = bufload('')
+  END
+  v9.CheckScriptFailure(lines, 'E1031: Cannot use void value')
+
+  # inside def: same error
+  lines =<< trim END
+    vim9script
+    def TestFunc()
+      var x = bufload('')
+    enddef
+    TestFunc()
+  END
+  v9.CheckScriptFailure(lines, 'E1031: Cannot use void value')
+
+  # script-level: echo void built-in
+  lines =<< trim END
+    vim9script
+    echo bufload('')
+  END
+  v9.CheckScriptFailure(lines, 'E1186: Expression does not result in a value: bufload(')
+
+  # inside def: compile-time error
+  lines =<< trim END
+    vim9script
+    def TestFunc()
+      echo bufload('')
+    enddef
+    TestFunc()
+  END
+  v9.CheckScriptFailure(lines, 'E1186: Expression does not result in a value: bufload(')
 enddef
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    301,
 /**/
     300,
 /**/