cgen: fix `x in shared_map` (#13442)

vlib/v/gen/c/infix_expr.v

@@ -430,9 +430,12 @@ fn (mut g Gen) infix_expr_in_op(node ast.InfixExpr) {
 			g.expr(node.left)
 		}
 		g.write(', ')
-		if !right.typ.is_ptr() {
+		if !right.typ.is_ptr() || right.typ.has_flag(.shared_f) {
 			g.write('ADDR(map, ')
 			g.expr(node.right)
+			if right.typ.has_flag(.shared_f) {
+				g.write('->val')
+			}
 			g.write(')')
 		} else {
 			g.expr(node.right)

vlib/v/tests/shared_map_test.v

@@ -155,3 +155,17 @@ fn test_shared_map_iteration() {
 	assert n1 == 1
 	assert n2 == 1
 }
+
+fn test_shared_map_in() {
+	shared m := {
+		'qwe': 12.75
+		'rtz': -0.125
+		'k':   17
+	}
+	rlock m {
+		assert 'qwe' in m
+		assert 'rtz' in m
+		assert 'k' in m
+		assert 'zxc' !in m
+	}
+}