fix missing syn feature

Author: msrd0

derive/Cargo.toml

@@ -20,4 +20,4 @@ regex = []
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = { version = "1.0", features = ["derive", "parsing", "printing", "proc-macro"], default-features = false }
+syn = { version = "1.0", features = ["clone-impls", "derive", "parsing", "printing", "proc-macro"], default-features = false }