checker: allow assign to a shared int var (fix #25986) (#25988)

Author: kbkpbot

vlib/v/checker/assign.v

@@ -649,7 +649,8 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 				}
 			}
 			right_is_ptr := right_type.is_any_kind_of_pointer()
-			if !right_is_ptr && node.op == .assign && right_type_unwrapped.is_number() {
+			if !left_type.has_flag(.shared_f) && !right_is_ptr && node.op == .assign
+				&& right_type_unwrapped.is_number() {
 				c.error('cannot assign to `${left}`: ' +
 					c.expected_msg(right_type_unwrapped, left_type_unwrapped), right.pos())
 			}

vlib/v/tests/shared_int_assign_test.v

@@ -0,0 +1,18 @@
+module main
+
+struct Foo {
+mut:
+	a shared int
+}
+
+fn test_main() {
+	mut x := Foo{}
+	lock x.a {
+		x.a = 100
+	}
+	rlock x.a {
+		k := x.a
+		// can't use assert x.a == 100, to be fixed
+		assert k == 100
+	}
+}