table,cgen: fix bug preventing `t := []thread{}` to compile (#8913)

vlib/v/gen/c/cgen.v

@@ -620,18 +620,19 @@ fn (mut g Gen) find_or_register_shared(t table.Type, base string) string {
 }
 
 fn (mut g Gen) register_thread_array_wait_call(eltyp string) string {
-	thread_typ := '__v_thread_$eltyp'
-	ret_typ := if eltyp == '' { 'void' } else { 'Array_$eltyp' }
+	is_void := eltyp == 'void'
+	thread_typ := if is_void { '__v_thread' } else { '__v_thread_$eltyp' }
+	ret_typ := if is_void { 'void' } else { 'Array_$eltyp' }
 	thread_arr_typ := 'Array_$thread_typ'
 	fn_name := '${thread_arr_typ}_wait'
 	if fn_name !in g.waiter_fns {
 		g.waiter_fns << fn_name
-		if eltyp == 'void' {
+		if is_void {
 			g.gowrappers.writeln('
 void ${fn_name}($thread_arr_typ a) {
 	for (int i = 0; i < a.len; ++i) {
 		$thread_typ t = (($thread_typ*)a.data)[i];
-		__v_thread_${eltyp}_wait(t);
+		__v_thread_wait(t);
 	}
 }')
 		} else {
@@ -5376,7 +5377,7 @@ fn (mut g Gen) write_types(types []table.TypeSymbol) {
 			}
 			table.Thread {
 				if g.pref.os == .windows {
-					if name == '__v_thread_void' {
+					if name == '__v_thread' {
 						g.type_definitions.writeln('typedef HANDLE $name;')
 					} else {
 						// Windows can only return `u32` (no void*) from a thread, so the
@@ -5869,8 +5870,11 @@ fn (mut g Gen) go_stmt(node ast.GoStmt, joinable bool) string {
 	if g.pref.os == .windows && node.call_expr.return_type != table.void_type {
 		g.writeln('$arg_tmp_var->ret_ptr = malloc(sizeof($s_ret_typ));')
 	}
-	gohandle_name := '__v_thread_' +
-		g.table.get_type_symbol(g.unwrap_generic(node.call_expr.return_type)).cname
+	gohandle_name := if node.call_expr.return_type == table.void_type {
+		'__v_thread'
+	} else {
+		'__v_thread_' + g.table.get_type_symbol(g.unwrap_generic(node.call_expr.return_type)).cname
+	}
 	if g.pref.os == .windows {
 		simple_handle := if joinable && node.call_expr.return_type != table.void_type {
 			'thread_handle_$tmp'

vlib/v/table/table.v

@@ -487,6 +487,9 @@ pub fn (t &Table) chan_cname(elem_type Type, is_mut bool) string {
 
 [inline]
 pub fn (t &Table) thread_name(return_type Type) string {
+	if return_type == void_type {
+		return 'thread'
+	}
 	return_type_sym := t.get_type_symbol(return_type)
 	ptr := if return_type.is_ptr() { '&' } else { '' }
 	return 'thread $ptr$return_type_sym.name'
@@ -494,6 +497,9 @@ pub fn (t &Table) thread_name(return_type Type) string {
 
 [inline]
 pub fn (t &Table) thread_cname(return_type Type) string {
+	if return_type == void_type {
+		return '__v_thread'
+	}
 	return_type_sym := t.get_type_symbol(return_type)
 	suffix := if return_type.is_ptr() { '_ptr' } else { '' }
 	return '__v_thread_$return_type_sym.cname$suffix'

vlib/v/table/types.v

@@ -540,7 +540,15 @@ pub fn (mut t Table) register_builtin_type_symbols() {
 		cname: 'int_literal'
 		mod: 'builtin'
 	)
-	t.register_type_symbol(kind: .thread, name: 'thread', cname: '__v_thread', mod: 'builtin')
+	t.register_type_symbol(
+		kind: .thread
+		name: 'thread'
+		cname: '__v_thread'
+		mod: 'builtin'
+		info: Thread{
+			return_type: table.void_type
+		}
+	)
 }
 
 [inline]

vlib/v/tests/go_array_wait_test.v

@@ -36,3 +36,16 @@ fn test_array_thread_void_wait() {
 	}
 }
 
+fn test_void_thread_decl() {
+	shared a := [2 3 9]
+	mut t1 := thread(0)
+	mut tarr := []thread{len: 2}
+	t1 = go g(shared a, 0)
+	tarr[0] = go g(shared a, 1)
+	tarr[1] = go g(shared a, 2)
+	t1.wait()
+	tarr.wait()
+	rlock a {
+		assert a == [6, 12, 90]
+	}
+}