Add comment about d < 10 vs d < 64

Author: nilehmann

library/core/src/ascii/ascii_char.rs

@@ -509,6 +509,9 @@ impl AsciiChar {
     /// when writing code using this method, since the implementation doesn't
     /// need something really specific, not to make those other arguments do
     /// something useful. It might be tightened before stabilization.)
+    // Only `d < 64` is required for safety as described above, but we use `d < 10` as 
+    // in the `assert_unsafe_precondition` inside. See https://github.com/rust-lang/rust/pull/129374
+    // for some context about the discrepancy.
     #[cfg_attr(flux, flux::spec(fn(d: u8{d < 10}) -> Self))]
     #[unstable(feature = "ascii_char", issue = "110998")]
     #[inline]

library/core/src/num/niche_types.rs

@@ -53,7 +53,7 @@ macro_rules! define_valid_range_type {
             /// Immediate language UB if `val == 0`, as it violates the validity
             /// invariant of this type.
             #[inline]
-            #[cfg_attr(flux, flux::spec(fn (val: $int{ $low <= cast(val) && cast(val) <= $high }) -> Self[{val:cast(val)}]))] // NOTE: `val == 0` comments are stale(?)
+            #[cfg_attr(flux, flux::spec(fn (val: $int{ $low <= cast(val) && cast(val) <= $high }) -> Self[{val:cast(val)}]))]
             pub const unsafe fn new_unchecked(val: $int) -> Self {
                 // SAFETY: Caller promised that `val` is non-zero.
                 unsafe { $name(val) }