Use a union to reduce the size of SmallVec

Author: Amanieu

.travis.yml

@@ -5,10 +5,9 @@ rust:
   - stable
 script: |
   cargo build --verbose &&
-  cargo build --all-features --verbose &&
   cargo test --verbose &&
-  cargo test --all-features --verbose &&
   ([ $TRAVIS_RUST_VERSION != nightly ] || cargo test --verbose --no-default-features) &&
+  ([ $TRAVIS_RUST_VERSION != nightly ] || cargo test --verbose --features union) &&
   ([ $TRAVIS_RUST_VERSION != nightly ] || cargo bench --verbose bench)
 notifications:
   webhooks: http://build.servo.org:54856/travis

Cargo.toml

@@ -12,13 +12,16 @@ documentation = "http://doc.servo.org/smallvec/"
 
 [features]
 std = []
+union = []
 default = ["std"]
 
 [lib]
 name = "smallvec"
 path = "lib.rs"
 
 [dependencies]
+unreachable = "1.0.0"
+debug_unreachable = "0.1"
 serde = { version = "1", optional = true }
 
 [dev_dependencies]