Add test using generic type with multiple bounds

error[E0277]: the trait bound `T: UpperHex` is not satisfied
       --> tests/test_generics.rs:179:13
        |
    178 |     #[derive(Error, Debug)]
        |              ----- in this derive macro expansion
    179 |     #[error("0x{thing:x} 0x{thing:X}")]
        |             ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `UpperHex` is not implemented for `T`
        |
        = note: required for `&T` to implement `UpperHex`
    note: required by a bound in `core::fmt::rt::Argument::<'_>::new_upper_hex`
       --> $RUSTUP_HOME/toolchains/nightly-aarch64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:133:29
        |
    133 |     pub fn new_upper_hex<T: UpperHex>(x: &T) -> Argument<'_> {
        |                             ^^^^^^^^ required by this bound in `Argument::<'_>::new_upper_hex`
        = note: this error originates in the macro `$crate::format_args` which comes from the expansion of the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)

tests/test_generics.rs

@@ -172,3 +172,15 @@ fn test_no_bound_on_named_fmt() {
     let error = Error { thing: DebugOnly };
     assert_eq!(error.to_string(), "...");
 }
+
+#[test]
+fn test_multiple_bound() {
+    #[derive(Error, Debug)]
+    #[error("0x{thing:x} 0x{thing:X}")]
+    pub struct Error<T> {
+        thing: T,
+    }
+
+    let error = Error { thing: 0xFFi32 };
+    assert_eq!(error.to_string(), "0xff 0xFF");
+}