Bump `virtue` to 0.0.9 and add test for #537 (#591)

derive/Cargo.toml

@@ -19,4 +19,4 @@ description = "Implementation of #[derive(Encode, Decode)] for bincode"
 proc-macro = true
 
 [dependencies]
-virtue = "0.0.8"
+virtue = "0.0.9"

tests/issues.rs

@@ -24,6 +24,9 @@ mod issue_500;
 #[path = "issues/issue_523.rs"]
 mod issue_523;
 
+#[path = "issues/issue_537.rs"]
+mod issue_537;
+
 #[path = "issues/issue_547.rs"]
 mod issue_547;
 

tests/issues/issue_537.rs

@@ -0,0 +1,8 @@
+#![cfg(all(feature = "derive", feature = "std"))]
+
+use bincode::{Decode, Encode};
+
+#[derive(Encode, Decode)]
+struct Foo<Bar = ()> {
+    x: Bar,
+}