Fixes really incorrect tuple impls.

Author: Nathaniel Ringo

gc/src/trace.rs

@@ -113,7 +113,7 @@ macro_rules! simple_empty_finalize_trace {
     }
 }
 
-simple_empty_finalize_trace![isize, usize, bool, i8, u8, i16, u16, i32, u32, i64, u64, f32, f64, char, String, Path, PathBuf];
+simple_empty_finalize_trace![(), isize, usize, bool, i8, u8, i16, u16, i32, u32, i64, u64, f32, f64, char, String, Path, PathBuf];
 
 macro_rules! fn_finalize_trace_one {
     ($ty:ty $(,$args:ident)*) => {
@@ -139,9 +139,18 @@ macro_rules! fn_finalize_trace_group {
 }
 
 macro_rules! tuple_finalize_trace {
+    () => {};
     ($($args:ident),*) => {
         impl<$($args),*> Finalize for ($($args,)*) {}
-        unsafe impl<$($args),*> Trace for ($($args,)*) { unsafe_empty_trace!(); }
+        unsafe impl<$($args: $crate::Trace),*> Trace for ($($args,)*) {
+            custom_trace!(this, {
+                #[allow(non_snake_case, unused_unsafe)]
+                fn avoid_lints<$($args: $crate::Trace),*>(&($(ref $args,)*): &($($args,)*)) {
+                    unsafe { $(mark($args);)* }
+                }
+                avoid_lints(this)
+            });
+        }
     }
 }