Work around async_trait behavior

src/traverse.rs

@@ -736,8 +736,17 @@ fn diff_generics(
     let old_count = old_gen.own_counts();
     let new_count = new_gen.own_counts();
 
+    // NEEDSWORK: proper detection of what's going on here..
+    let was_async_trait_transformed = old_count.lifetimes > 0
+        && old_gen.params[old_count.lifetimes - 1].name.as_str() == "'async_trait";
+
     let self_add = if old_gen.has_self && new_gen.has_self {
-        1
+        if was_async_trait_transformed {
+            // async_trait transformation undoes the self lifetime?
+            0
+        } else {
+            1
+        }
     } else if !old_gen.has_self && !new_gen.has_self {
         0
     } else {

tests/full.rs

@@ -173,6 +173,8 @@ mod full {
     full_test!(libc0, "libc", "0.2.28", "0.2.31", cfg!(windows));
     full_test!(libc1, "libc", "0.2.47", "0.2.48", true);
     full_test!(rmpv, "rmpv", "0.4.0", "0.4.1", false);
+    // NOTE: this one is a regression test for the async-trait workaround (#295) mostly
+    full_test!(async_trait, "config", "0.13.0", "0.13.1", false);
     // full_test!(mozjs, "mozjs", "0.2.0", "0.3.0");
     // full_test!(rand, "rand", "0.3.10", "0.3.16");
     // full_test!(serde_pre, "serde", "0.7.0", "1.0.0");