cgen: fix threads array wait without go calls (fix #12009) (#12050)

vlib/v/gen/c/cgen.v

@@ -887,6 +887,23 @@ fn (mut g Gen) write_shareds() {
 	}
 }
 
+fn (mut g Gen) register_thread_void_wait_call() {
+	if '__v_thread_wait' !in g.waiter_fns {
+		g.gowrappers.writeln('void __v_thread_wait(__v_thread thread) {')
+		if g.pref.os == .windows {
+			g.gowrappers.writeln('\tu32 stat = WaitForSingleObject(thread, INFINITE);')
+		} else {
+			g.gowrappers.writeln('\tint stat = pthread_join(thread, (void **)NULL);')
+		}
+		g.gowrappers.writeln('\tif (stat != 0) { _v_panic(_SLIT("unable to join thread")); }')
+		if g.pref.os == .windows {
+			g.gowrappers.writeln('\tCloseHandle(thread);')
+		}
+		g.gowrappers.writeln('}')
+		g.waiter_fns << '__v_thread_wait'
+	}
+}
+
 fn (mut g Gen) register_thread_array_wait_call(eltyp string) string {
 	is_void := eltyp == 'void'
 	thread_typ := if is_void { '__v_thread' } else { '__v_thread_$eltyp' }
@@ -896,6 +913,7 @@ fn (mut g Gen) register_thread_array_wait_call(eltyp string) string {
 	if fn_name !in g.waiter_fns {
 		g.waiter_fns << fn_name
 		if is_void {
+			g.register_thread_void_wait_call()
 			g.gowrappers.writeln('
 void ${fn_name}($thread_arr_typ a) {
 	for (int i = 0; i < a.len; ++i) {

vlib/v/parser/parse_type.v

@@ -70,6 +70,9 @@ pub fn (mut p Parser) parse_array_type() ast.Type {
 		// error is set in parse_type
 		return 0
 	}
+	if elem_type.idx() == ast.thread_type_idx {
+		p.register_auto_import('sync.threads')
+	}
 	mut nr_dims := 1
 	// detect attr
 	not_attr := p.peek_tok.kind != .name && p.peek_token(2).kind !in [.semicolon, .rsbr]

vlib/v/tests/go_array_wait_without_go_test.v

@@ -0,0 +1,27 @@
+fn test_go_array_wait_without_go() {
+	sa := SA{}
+	sb := SA{}
+
+	sa.wait()
+	sb.wait()
+
+	assert true
+}
+
+struct SA {
+mut:
+	threads []thread
+}
+
+pub fn (self SA) wait() {
+	self.threads.wait()
+}
+
+struct SB {
+mut:
+	threads []thread
+}
+
+pub fn (self SB) wait() {
+	self.threads.wait()
+}