Add a note saying that {u8,i8}::from_{be,le,ne}_bytes is meaningless

Author: tbu-

library/core/src/num/mod.rs

@@ -77,6 +77,31 @@ pub use saturating::Saturating;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use wrapping::Wrapping;
 
+macro_rules! u8_xe_bytes_doc {
+ () => {
+ "
+
+**Note**: This function is meaningless on `u8`. Byte order does not exist as a
+concept for byte-sized integers. This function is only provided in symmetry
+with larger integer types.
+
+"
+ };
+}
+
+macro_rules! i8_xe_bytes_doc {
+ () => {
+ "
+
+**Note**: This function is meaningless on `i8`. Byte order does not exist as a
+concept for byte-sized integers. This function is only provided in symmetry
+with larger integer types. You can cast from and to `u8` using `as i8` and `as
+u8`.
+
+"
+ };
+}
+
 macro_rules! usize_isize_to_xe_bytes_doc {
  () => {
  "
@@ -348,8 +373,8 @@ impl i8 {
  reversed = "0x48",
  le_bytes = "[0x12]",
  be_bytes = "[0x12]",
- to_xe_bytes_doc = "",
- from_xe_bytes_doc = "",
+ to_xe_bytes_doc = i8_xe_bytes_doc!(),
+ from_xe_bytes_doc = i8_xe_bytes_doc!(),
  bound_condition = "",
  }
  midpoint_impl! { i8, i16, signed }
@@ -547,8 +572,8 @@ impl u8 {
  reversed = "0x48",
  le_bytes = "[0x12]",
  be_bytes = "[0x12]",
- to_xe_bytes_doc = "",
- from_xe_bytes_doc = "",
+ to_xe_bytes_doc = u8_xe_bytes_doc!(),
+ from_xe_bytes_doc = u8_xe_bytes_doc!(),
  bound_condition = "",
  }
  widening_impl! { u8, u16, 8, unsigned }