Rollup merge of rust-lang#138546 - GuillaumeGomez:integer-to-string-tests, r=Amanieu

Add integer to string formatting tests

As discussed in rust-lang#136264, there doesn't seem to have tests to ensure that int to string conversion is performed correctly, only sporadic tests here and there. Now we have some basic tests. :)

r? ````@Mark-Simulacrum````

Author: matthiaskrgr

library/alloctests/tests/lib.rs

@@ -63,6 +63,7 @@ mod fmt;
 mod heap;
 mod linked_list;
 mod misc_tests;
+mod num;
 mod rc;
 mod slice;
 mod sort;

library/alloctests/tests/num.rs

@@ -0,0 +1,69 @@
+use std::fmt::{Debug, Display};
+use std::str::FromStr;
+
+fn assert_nb<Int: ToString + FromStr + Debug + Display + Eq>(value: Int) {
+    let s = value.to_string();
+    let s2 = format!("s: {}.", value);
+
+    assert_eq!(format!("s: {s}."), s2);
+    let Ok(ret) = Int::from_str(&s) else {
+        panic!("failed to convert into to string");
+    };
+    assert_eq!(ret, value);
+}
+
+macro_rules! uint_to_s {
+    ($($fn_name:ident, $int:ident,)+) => {
+        $(
+            #[test]
+            fn $fn_name() {
+                assert_nb::<$int>($int::MIN);
+                assert_nb::<$int>($int::MAX);
+                assert_nb::<$int>(1);
+                assert_nb::<$int>($int::MIN / 2);
+                assert_nb::<$int>($int::MAX / 2);
+            }
+        )+
+    }
+}
+macro_rules! int_to_s {
+    ($($fn_name:ident, $int:ident,)+) => {
+        $(
+            #[test]
+            fn $fn_name() {
+                assert_nb::<$int>($int::MIN);
+                assert_nb::<$int>($int::MAX);
+                assert_nb::<$int>(1);
+                assert_nb::<$int>(0);
+                assert_nb::<$int>(-1);
+                assert_nb::<$int>($int::MIN / 2);
+                assert_nb::<$int>($int::MAX / 2);
+            }
+        )+
+    }
+}
+
+int_to_s!(
+    test_i8_to_string,
+    i8,
+    test_i16_to_string,
+    i16,
+    test_i32_to_string,
+    i32,
+    test_i64_to_string,
+    i64,
+    test_i128_to_string,
+    i128,
+);
+uint_to_s!(
+    test_u8_to_string,
+    u8,
+    test_u16_to_string,
+    u16,
+    test_u32_to_string,
+    u32,
+    test_u64_to_string,
+    u64,
+    test_u128_to_string,
+    u128,
+);