Merge pull request #377 from dtolnay/bounds

Support generic types that need multiple bounds

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;

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");
+}