fix range_do_eq

crates/sui-framework/packages/move-stdlib/sources/macros.move

@@ -64,8 +64,14 @@ module std::macros {
         let start = $start;
         let stop = $stop;
         let mut i = start;
-        while (i <= stop) {
+        // we check `i >= stop` inside the loop instead of `i <= stop` as `while` consition to avoid
+        // incrementing `i` past the MAX integer value.
+        // Because of this, we need to check if `start > stop` and return early, instead
+        // of letting the loop bound handle it, like in the `range_do` macro.
+        if (start > stop) return;
+        loop {
             $f(i);
+            if (i >= stop) break;
             i = i + 1;
         }
     }

crates/sui-framework/packages/move-stdlib/tests/integer_tests.move

@@ -203,6 +203,10 @@ module std::integer_tests {
             case_succ.range_do_eq!(case, |_| assert!(false));
         });
 
+        // test upper bound being max
+        let max_pred = max - 1;
+        max_pred.range_do_eq!(max, |_| ());
+
         // test iteration numbers
         let cases: vector<$T> = vector[3, 5, 8, 11, 14];
         cases!(max, cases, |case_pred, case, case_succ| {

crates/sui-framework/packages/move-stdlib/tests/u8_tests.move

@@ -4,6 +4,7 @@
 #[test_only]
 module std::u8_tests {
     use std::integer_tests;
+    use std::unit_test::assert_eq;
 
     const BIT_SIZE: u8 = 8;
     const MAX: u8 = 0xFF;
@@ -68,6 +69,9 @@ module std::u8_tests {
 
     #[test]
     fun test_dos() {
+        let mut sum = 0u16;
+        255u8.do_eq!(|i| sum = sum + (i as u16));
+        assert_eq!(sum, 32640);
         integer_tests::test_dos!(MAX, CASES);
     }
 }