gnu: Add rust-enum-as-inner-0.3.

* gnu/packages/crates-io.scm (rust-enum-as-inner-0.3): New variable.

gnu/packages/crates-io.scm

@@ -7177,6 +7177,31 @@ Standard.")
      "Streaming transcoding for encoding_rs.")
     (license (list license:asl2.0 license:expat))))
 
+(define-public rust-enum-as-inner-0.3
+  (package
+    (name "rust-enum-as-inner")
+    (version "0.3.3")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "enum-as-inner" version))
+       (file-name (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "15gmpgywijda93lkq7hf2y53h66sqkhzabzbxich288xm6b00pvw"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-heck" ,rust-heck-0.3)
+        ("rust-proc-macro2" ,rust-proc-macro2-1)
+        ("rust-quote" ,rust-quote-1)
+        ("rust-syn" ,rust-syn-1))))
+    (home-page "https://github.com/bluejekyll/enum-as-inner")
+    (synopsis "Proc-macro for deriving inner field accessor functions on enums")
+    (description "This package provides a proc-macro for deriving inner field
+accessor functions on enums.")
+    (license (list license:expat license:asl2.0))))
+
 (define-public rust-env-logger-0.7
   (package
     (name "rust-env-logger")