fix

vlib/v/ast/table.v

@@ -1952,6 +1952,17 @@ pub fn (mut t Table) unwrap_generic_type(typ Type, generic_names []string, concr
 			nrt += ']'
 			idx := t.type_idxs[nrt]
 			if idx != 0 && t.type_symbols[idx].kind != .placeholder {
+				fields = ts.info.fields.clone()
+				for i in 0 .. fields.len {
+					if fields[i].typ.has_flag(.generic) {
+						// Map[T], []Type[T]
+						if fields[i].typ.has_flag(.generic)
+							&& t.type_kind(fields[i].typ) in [.array, .array_fixed, .map]
+							&& t.check_if_elements_need_unwrap(typ, fields[i].typ) {
+							t.unwrap_generic_type(fields[i].typ, t_generic_names, t_concrete_types)
+						}
+					}
+				}
 				return new_type(idx).derive(typ).clear_flag(.generic)
 			} else {
 				// fields type translate to concrete type

vlib/v/tests/structs/struct_array_generic_field_test.v

@@ -0,0 +1,58 @@
+// callback types
+type CBnoret[T] = fn (val T)
+
+type CBnoret2[T] = fn (val T, prev T)
+
+type CBvret[T] = fn (val T) T
+
+type CBvret2[T] = fn (val T, prev T) T
+
+type Callback[T] = CBnoret[T] | CBnoret2[T] | CBvret[T] | CBvret2[T]
+
+interface IObv[T] {
+	v    T
+	prev T
+	cb   []Callback[T]
+}
+
+struct Obv[T] {
+mut:
+	v    T
+	prev T
+	cb   []Callback[T]
+}
+
+fn (o Obv[T]) get() T {
+	return o.v
+}
+
+fn (o Obv[T]) do_callbacks() T {
+	return o.v
+}
+
+fn (mut o Obv[T]) set(new_value T) T {
+	prev := o.v
+	if prev != new_value {
+		o.v = new_value
+		o.prev = prev
+	}
+
+	return o.v
+}
+
+fn oo[T](init T) Obv[T] {
+	return Obv[T]{
+		v: init
+	}
+}
+
+fn test_main() {
+	one := oo(1)
+	txt := oo('lala')
+
+	println('txt: ${txt.get()}')
+	println('one: ${one.get()}')
+
+	assert txt.get() == 'lala'
+	assert one.get() == 1
+}