Commits on Jan 26, 2024

1. Fix proc macro panicked with Invalid type in const_random! in R… …

   …ust 1.77.
   
   With Rust nightly 1.77, any invocation of `const_random!` with a `u8`
   array causes a compile-time panic. This can be seen when running `cargo
   test`:
   ```
   error: proc macro panicked
     --> tests/tests.rs:52:28
      |
   52 |     const VALUE1: &[u8] = &const_random!([u8; 30]);
      |                            ^^^^^^^^^^^^^^^^^^^^^^^
      |
      = help: message: Invalid type
   ```
   This is because the proc macro starts by calling `to_string` on the
   input token stream, and then uses substring matching to "parse" it. In
   Rust 1.77 the `Display` impl for `TokenStream` has changed, and what
   used to be converted to the string `"[u8 ; 30]"` is now `"[u8; 30]"`. As
   a result, the `byte_array.starts_with("[u8 ; ")` call fails.
   
   Note that substring matching is inherently flawed because the whitespace
   in the output of `to_string` is not guaranteed.
   
   This commit rewrites the proc macro to be robust in the face of
   `to_string` whitespace changes, by iterating over the individual
   `TokenTrees`s.
   
   The commit also adds a comment explaining why `usize` and `isize` are
   handled differently, because it's subtle.
   
   Note: I ran `cargo fmt` within `macro/` to format the changes to
   `macro/src/lib.rs` and it made some minor changes to `macro/src/span.rs`
   as well.

   

   nnethercote committed Jan 26, 2024
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