all: assigning 0 to reference fields now requires unsafe blocks (fix #14911) (#19955)

vlib/builtin/map.v

@@ -99,7 +99,7 @@ fn new_dense_array(key_bytes int, value_bytes int) DenseArray {
 		cap: cap
 		len: 0
 		deletes: 0
-		all_deleted: 0
+		all_deleted: unsafe { nil }
 		keys: unsafe { malloc(__at_least_one(u64(cap) * u64(key_bytes))) }
 		values: unsafe { malloc(__at_least_one(u64(cap) * u64(value_bytes))) }
 	}
@@ -679,9 +679,9 @@ fn (d &DenseArray) clone() DenseArray {
 		cap: d.cap
 		len: d.len
 		deletes: d.deletes
-		all_deleted: 0
+		all_deleted: unsafe { nil }
-		values: 0
+		values: unsafe { nil }
-		keys: 0
+		keys: unsafe { nil }
 	}
 	unsafe {
 		if d.deletes != 0 {

vlib/builtin/map_d_gcboehm_opt.v

@@ -23,7 +23,7 @@ fn new_dense_array_noscan(key_bytes int, key_noscan bool, value_bytes int, value
 		cap: cap
 		len: 0
 		deletes: 0
-		all_deleted: 0
+		all_deleted: unsafe { nil }
 		keys: __malloc_at_least_one(u64(cap) * u64(key_bytes), key_noscan)
 		values: __malloc_at_least_one(u64(cap) * u64(value_bytes), value_noscan)
 	}

vlib/gg/gg.c.v

@@ -445,7 +445,7 @@ pub fn new_context(cfg Config) &Context {
 		width: cfg.width
 		height: cfg.height
 		config: cfg
-		ft: 0
+		ft: unsafe { nil }
 		ui_mode: cfg.ui_mode
 		native_rendering: cfg.native_rendering
 		window: sapp.Desc{

vlib/net/urllib/urllib.v

@@ -470,7 +470,7 @@ fn parse_url(rawurl string, via_request bool) !URL {
 		return error(error_msg('parse_url: empty URL', rawurl))
 	}
 	mut url := URL{
-		user: 0
+		user: unsafe { nil }
 	}
 	if rawurl == '*' {
 		url.path = '*'

vlib/os/os_windows.c.v

@@ -328,10 +328,10 @@ pub fn raw_execute(cmd string) Result {
 	}
 	proc_info := ProcessInformation{}
 	start_info := StartupInfo{
-		lp_reserved2: 0
+		lp_reserved2: unsafe { nil }
-		lp_reserved: 0
+		lp_reserved: unsafe { nil }
-		lp_desktop: 0
+		lp_desktop: unsafe { nil }
-		lp_title: 0
+		lp_title: unsafe { nil }
 		cb: sizeof(C.PROCESS_INFORMATION)
 		h_std_input: child_stdin
 		h_std_output: child_stdout_write

vlib/os/process_windows.c.v

@@ -68,18 +68,18 @@ fn (mut p Process) win_spawn_process() int {
 	}
 	p.filename = abs_path(p.filename) // expand the path to an absolute one, in case we later change the working folder
 	mut wdata := &WProcess{
-		child_stdin: 0
+		child_stdin: unsafe { nil }
-		child_stdout_read: 0
+		child_stdout_read: unsafe { nil }
-		child_stdout_write: 0
+		child_stdout_write: unsafe { nil }
-		child_stderr_read: 0
+		child_stderr_read: unsafe { nil }
-		child_stderr_write: 0
+		child_stderr_write: unsafe { nil }
 	}
 	p.wdata = voidptr(wdata)
 	mut start_info := StartupInfo{
-		lp_reserved2: 0
+		lp_reserved2: unsafe { nil }
-		lp_reserved: 0
+		lp_reserved: unsafe { nil }
-		lp_desktop: 0
+		lp_desktop: unsafe { nil }
-		lp_title: 0
+		lp_title: unsafe { nil }
 		cb: sizeof(C.PROCESS_INFORMATION)
 	}
 	if p.use_stdio_ctl {

vlib/sync/channels.c.v

@@ -82,8 +82,8 @@ fn new_channel_st(n u32, st u32) &Channel {
 		read_avail: 0
 		ringbuf: rbuf
 		statusbuf: sbuf
-		write_subscriber: 0
+		write_subscriber: unsafe { nil }
-		read_subscriber: 0
+		read_subscriber: unsafe { nil }
 	}
 	ch.writesem.init(wsem)
 	ch.readsem.init(rsem)
@@ -105,8 +105,8 @@ fn new_channel_st_noscan(n u32, st u32) &Channel {
 			read_avail: 0
 			ringbuf: rbuf
 			statusbuf: sbuf
-			write_subscriber: 0
+			write_subscriber: unsafe { nil }
-			read_subscriber: 0
+			read_subscriber: unsafe { nil }
 		}
 		ch.writesem.init(wsem)
 		ch.readsem.init(rsem)

vlib/v/ast/table.v

@@ -96,9 +96,9 @@ pub fn (t &Table) panic(message string) {
 pub fn new_table() &Table {
 	mut t := &Table{
 		global_scope: &Scope{
-			parent: 0
+			parent: unsafe { nil }
 		}
-		cur_fn: 0
+		cur_fn: unsafe { nil }
 	}
 	t.register_builtin_type_symbols()
 	t.is_fmt = true

vlib/v/checker/checker.v

@@ -335,7 +335,7 @@ pub fn (mut c Checker) check_files(ast_files []&ast.File) {
 					file: the_main_file.path
 					return_type: ast.void_type
 					scope: &ast.Scope{
-						parent: 0
+						parent: nil
 					}
 				}
 				has_main_fn = true
@@ -2021,7 +2021,7 @@ fn (mut c Checker) stmt(mut node ast.Stmt) {
 				if mut id.info is ast.IdentVar {
 					if id.comptime && id.name in ast.valid_comptime_not_user_defined {
 						node.defer_vars[i] = ast.Ident{
-							scope: 0
+							scope: unsafe { nil }
 							name: ''
 						}
 						continue

vlib/v/checker/struct.v

@@ -691,10 +691,19 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 							init_field.pos)
 					}
 				} else {
-					if exp_type.is_ptr() && !got_type.is_any_kind_of_pointer()
+					is_unsafe_0 := init_field.expr is ast.UnsafeExpr
-						&& init_field.expr.str() != '0' && !exp_type.has_flag(.option) {
+						&& (init_field.expr as ast.UnsafeExpr).expr.str() == '0'
-						c.error('reference field must be initialized with reference',
+					if exp_type.is_ptr() && !is_unsafe_0 && !got_type.is_any_kind_of_pointer()
-							init_field.pos)
+						&& !exp_type.has_flag(.option) {
+						if init_field.expr.str() == '0' {
+							if !c.inside_unsafe && type_sym.language == .v {
+								c.note('assigning `0` to a reference field is only allowed in `unsafe` blocks',
+									init_field.pos)
+							}
+						} else {
+							c.error('reference field must be initialized with reference',
+								init_field.pos)
+						}
 					} else if exp_type.is_pointer() && !got_type.is_any_kind_of_pointer()
 						&& !got_type.is_int() {
 						got_typ_str := c.table.type_to_str(got_type)

vlib/v/checker/tests/struct_ref_fields_init_0_err.out

@@ -0,0 +1,14 @@
+vlib/v/checker/tests/struct_ref_fields_init_0_err.vv:6:10: notice: assigning `0` to a reference field is only allowed in `unsafe` blocks
+    4 | 
+    5 | fn main() {
+    6 |     _ = Foo{0}
+      |             ^
+    7 |     _ = Foo{
+    8 |         foo: 0
+vlib/v/checker/tests/struct_ref_fields_init_0_err.vv:8:3: notice: assigning `0` to a reference field is only allowed in `unsafe` blocks
+    6 |     _ = Foo{0}
+    7 |     _ = Foo{
+    8 |         foo: 0
+      |         ~~~~~~
+    9 |     }
+   10 | }

vlib/v/checker/tests/struct_ref_fields_init_0_err.vv

@@ -0,0 +1,10 @@
+struct Foo {
+	foo &u8
+}
+
+fn main() {
+	_ = Foo{0}
+	_ = Foo{
+		foo: 0
+	}
+}

vlib/v/gen/c/assign.v

@@ -215,7 +215,7 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 		mut gen_or := false
 		mut blank_assign := false
 		mut ident := ast.Ident{
-			scope: 0
+			scope: unsafe { nil }
 		}
 		left_sym := g.table.sym(g.unwrap_generic(var_type))
 		if mut left is ast.Ident {
@@ -781,7 +781,7 @@ fn (mut g Gen) gen_multi_return_assign(node &ast.AssignStmt, return_type ast.Typ
 	for i, lx in node.left {
 		mut is_auto_heap := false
 		mut ident := ast.Ident{
-			scope: 0
+			scope: unsafe { nil }
 		}
 		if lx is ast.Ident {
 			ident = lx

vlib/v/gen/c/cgen.v

@@ -279,7 +279,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref_ &pref.Preferences) (string
 	}
 	mut reflection_strings := map[string]int{}
 	mut global_g := Gen{
-		file: 0
+		file: unsafe { nil }
 		out: strings.new_builder(512000)
 		cheaders: strings.new_builder(15000)
 		includes: strings.new_builder(100)
@@ -308,7 +308,7 @@ pub fn gen(files []&ast.File, table &ast.Table, pref_ &pref.Preferences) (string
 		sql_buf: strings.new_builder(100)
 		table: table
 		pref: pref_
-		fn_decl: 0
+		fn_decl: unsafe { nil }
 		is_autofree: pref_.autofree
 		indent: -1
 		module_built: module_built
@@ -662,7 +662,7 @@ fn cgen_process_one_file_cb(mut p pool.PoolProcessor, idx int, wid int) &Gen {
 		cleanup: strings.new_builder(100)
 		table: global_g.table
 		pref: global_g.pref
-		fn_decl: 0
+		fn_decl: unsafe { nil }
 		indent: -1
 		module_built: global_g.module_built
 		timers: util.new_timers(
@@ -3994,7 +3994,7 @@ fn (mut g Gen) lock_expr(node ast.LockExpr) {
 	g.cur_lock = unsafe { node } // is ok because it is discarded at end of fn
 	defer {
 		g.cur_lock = ast.LockExpr{
-			scope: 0
+			scope: unsafe { nil }
 		}
 	}
 	tmp_result := if node.is_expr { g.new_tmp_var() } else { '' }

vlib/v/gen/c/orm.v

@@ -1025,7 +1025,7 @@ fn (mut g Gen) write_orm_select(node ast.SqlExpr, connection_var_name string, re
 					expr: right_where_expr
 					expr_type: (right_where_expr.info as ast.IdentVar).typ
 					typ: (right_where_expr.info as ast.IdentVar).typ
-					scope: 0
+					scope: unsafe { nil }
 				}
 				mut sql_expr_select_array := ast.SqlExpr{
 					typ: field.typ.set_flag(.result)

vlib/v/parser/comptime.v

@@ -102,7 +102,7 @@ fn (mut p Parser) hash() ast.HashStmt {
 
 fn (mut p Parser) comptime_call() ast.ComptimeCall {
 	err_node := ast.ComptimeCall{
-		scope: 0
+		scope: unsafe { nil }
 	}
 	start_pos := p.tok.pos()
 	p.check(.dollar)
@@ -130,7 +130,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 		p.check(.string)
 		p.check(.rpar)
 		return ast.ComptimeCall{
-			scope: 0
+			scope: unsafe { nil }
 			method_name: method_name
 			args_var: s
 			is_env: method_name == 'env'
@@ -149,14 +149,14 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 		p.check(.rpar)
 		if has_args {
 			return ast.ComptimeCall{
-				scope: 0
+				scope: unsafe { nil }
 				method_name: method_name
 				args_var: type_index
 				pos: start_pos.extend(p.prev_tok.pos())
 			}
 		}
 		return ast.ComptimeCall{
-			scope: 0
+			scope: unsafe { nil }
 			method_name: method_name
 			pos: start_pos.extend(p.prev_tok.pos())
 		}
@@ -197,7 +197,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 			p.register_auto_import('v.preludes.embed_file.zlib')
 		}
 		return ast.ComptimeCall{
-			scope: 0
+			scope: unsafe { nil }
 			is_embed: true
 			embed_file: ast.EmbeddedFile{
 				compression_type: embed_compression_type
@@ -233,7 +233,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 		if !os.exists(path) {
 			if p.pref.is_fmt {
 				return ast.ComptimeCall{
-					scope: 0
+					scope: unsafe { nil }
 					is_vweb: true
 					method_name: method_name
 					args_var: literal_string_param
@@ -274,7 +274,7 @@ fn (mut p Parser) comptime_call() ast.ComptimeCall {
 	mut file := parse_comptime(tmpl_path, v_code, p.table, p.pref, p.scope)
 	file.path = tmpl_path
 	return ast.ComptimeCall{
-		scope: 0
+		scope: unsafe { nil }
 		is_vweb: true
 		vweb_tmpl: file
 		method_name: method_name

vlib/v/parser/fn.v

@@ -289,7 +289,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	if p.tok.kind == .lpar {
 		is_method = true
 		p.fn_receiver(mut params, mut rec) or { return ast.FnDecl{
-			scope: 0
+			scope: unsafe { nil }
 		} }
 
 		// rec.language was initialized with language variable.
@@ -321,7 +321,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			p.error_with_pos('function names cannot contain uppercase letters, use snake_case instead',
 				name_pos)
 			return ast.FnDecl{
-				scope: 0
+				scope: unsafe { nil }
 			}
 		}
 		if is_method {
@@ -336,7 +336,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			if is_duplicate {
 				p.error_with_pos('duplicate method `${name}`', name_pos)
 				return ast.FnDecl{
-					scope: 0
+					scope: unsafe { nil }
 				}
 			}
 		}
@@ -344,7 +344,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			if name in p.imported_symbols {
 				p.error_with_pos('cannot redefine imported function `${name}`', name_pos)
 				return ast.FnDecl{
-					scope: 0
+					scope: unsafe { nil }
 				}
 			}
 		}
@@ -374,7 +374,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	} else {
 		p.error_with_pos('expecting method name', p.tok.pos())
 		return ast.FnDecl{
-			scope: 0
+			scope: unsafe { nil }
 		}
 	}
 	// [T]
@@ -386,7 +386,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			fn_generic_names := generic_names.clone()
 			generic_names = p.types_to_names(sym.info.generic_types, p.tok.pos(), 'sym.info.generic_types') or {
 				return ast.FnDecl{
-					scope: 0
+					scope: unsafe { nil }
 				}
 			}
 			for gname in fn_generic_names {
@@ -407,7 +407,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			if p.scope.known_var(param.name) {
 				p.error_with_pos('redefinition of parameter `${param.name}`', param.pos)
 				return ast.FnDecl{
-					scope: 0
+					scope: unsafe { nil }
 				}
 			}
 			is_stack_obj := !param.typ.has_flag(.shared_f) && (param.is_mut || param.typ.is_ptr())
@@ -483,7 +483,7 @@ run them via `v file.v` instead',
 			p.error_with_pos('cannot define new methods on non-local type ${type_sym.name}',
 				rec.type_pos)
 			return ast.FnDecl{
-				scope: 0
+				scope: unsafe { nil }
 			}
 		}
 		type_sym_method_idx = type_sym.register_method(ast.Fn{
@@ -585,7 +585,7 @@ run them via `v file.v` instead',
 	if !no_body && are_params_type_only {
 		p.error_with_pos('functions with type only params can not have bodies', body_start_pos)
 		return ast.FnDecl{
-			scope: 0
+			scope: unsafe { nil }
 		}
 	}
 	// if no_body && !name.starts_with('C.') {

vlib/v/parser/parser.v

@@ -262,7 +262,7 @@ pub fn parse_vet_file(path string, table_ &ast.Table, pref_ &pref.Preferences) (
 		eprintln('> ${@MOD}.${@FN} path: ${path}')
 	}
 	global_scope := &ast.Scope{
-		parent: 0
+		parent: unsafe { nil }
 	}
 	mut p := Parser{
 		scanner: scanner.new_scanner_file(path, .parse_comments, pref_) or { panic(err) }
@@ -1194,7 +1194,7 @@ fn (mut p Parser) asm_stmt(is_top_level bool) ast.AsmStmt {
 
 	p.check(.lcbr)
 	p.scope = &ast.Scope{
-		parent: 0 // you shouldn't be able to reference other variables in assembly blocks
+		parent: unsafe { nil } // you shouldn't be able to reference other variables in assembly blocks
 		detached_from_parent: true
 		start_pos: p.tok.pos
 		objects: ast.all_registers(mut p.table, arch) //
@@ -4295,7 +4295,7 @@ fn (mut p Parser) assoc() ast.Assoc {
 	mut v := p.scope.find_var(var_name) or {
 		p.error('unknown variable `${var_name}`')
 		return ast.Assoc{
-			scope: 0
+			scope: unsafe { nil }
 		}
 	}
 	v.is_used = true