From fb8d3a7f448aa2db8e9bb13fae03c687f64d112b Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Fri, 8 Nov 2024 12:43:16 -0500
Subject: [PATCH 1/2] 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 | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/test_generics.rs b/tests/test_generics.rs
index 4d49edf5..36f11811 100644
--- a/tests/test_generics.rs
+++ b/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");
+}

From 5948ee6ce45031a4520f7a6a345df36bf8a33be0 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Fri, 8 Nov 2024 12:48:02 -0500
Subject: [PATCH 2/2] Support generic types that need multiple bounds

---
 impl/src/fmt.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/impl/src/fmt.rs b/impl/src/fmt.rs
index 36300e52..6dfdccf2 100644
--- a/impl/src/fmt.rs
+++ b/impl/src/fmt.rs
@@ -99,10 +99,6 @@ impl Display<'_> {
                 formatvar = IdentUnraw::new(format_ident!("_{}", formatvar.to_string()));
             }
             out += &formatvar.to_string();
-            if !macro_named_args.insert(member.clone()) {
-                // Already added to scope by a previous use.
-                continue;
-            }
             let local = formatvar.to_local();
             let mut binding_value = ToTokens::into_token_stream(match &member {
                 MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
@@ -142,7 +138,11 @@ impl Display<'_> {
                     }
                 );
             }
-            bindings.push((local, binding_value));
+            if macro_named_args.insert(member) {
+                bindings.push((local, binding_value));
+            } else {
+                // Already added to bindings by a previous use.
+            }
         }
 
         out += read;