rust: Add a "nightly" feature

The `clear_on_drop` crate supports zeroing using Rust intrinsics on
nightly (as opposed to the stable solution of linking against a small C
shim).

This exposes it as a "nightly" feature

.travis.yml

@@ -9,6 +9,10 @@ matrix:
   allow_failures:
   - rust: nightly
   include:
+  - language: csharp
+    mono: none
+    dotnet: 2.0.0
+    before_script: cd dotnet
   - language: go
     go: 1.9
     before_script: cd go
@@ -34,8 +38,8 @@ matrix:
     rust: stable
     before_script: cd rust
     env:
-      - RUSTFLAGS=-Ctarget-feature=+aes
       - CARGO_FEATURES=--features="aes-soft"
+      - RUSTFLAGS=-Ctarget-feature=+aes
   - language: rust
     rust: stable
     before_script: cd rust
@@ -45,12 +49,13 @@ matrix:
     rust: nightly
     before_script: cd rust
     env:
+      - CARGO_FEATURES=--features="aes-soft,nightly"
       - RUSTFLAGS=-Ctarget-feature=+aes
-      - CARGO_FEATURES=--features="aes-soft"
   - language: rust
     rust: nightly
     before_script: cd rust
     env:
+      - CARGO_FEATURES=--features="aes-soft,nightly"
       - RUSTFLAGS=-Ctarget-feature=+aes
   - language: rust
     rust: nightly
@@ -62,8 +67,3 @@ matrix:
     script:
       - make
       - ./ffi_test
-
-  - language: csharp
-    mono: none
-    dotnet: 2.0.0
-    before_script: cd dotnet

rust/Cargo.toml

@@ -18,7 +18,7 @@ aes = "0.1.0"
 crypto-mac = "0.6"
 block-modes = "0.1"
 byteorder = { version = "1.2", default-features = false }
-clear_on_drop = { version = "0.2" }
+clear_on_drop = "0.2"
 cmac = "0.1"
 dbl = "0.1"
 pmac = "0.1"
@@ -30,11 +30,12 @@ data-encoding = "2.0"
 serde_json = "1"
 
 [features]
+aes-soft = ["aes/force_soft"]
 bench = ["ring"]
 default = ["std"]
+nightly = ["clear_on_drop/nightly"]
 staticlib = []
 std = []
-aes-soft = ["aes/force_soft"]
 
 [profile.release]
 opt-level = 3

rust/ci.sh

@@ -2,4 +2,4 @@
 
 set -e
 
-cargo test $CARGO_FEATURES
+cargo test $CARGO_FEATURES