Add const-generics feature

Author: survived

Cargo.toml

@@ -28,6 +28,7 @@ travis-ci = { repository = "dalek-cryptography/subtle", branch = "master"}
 rand = { version = "0.7" }
 
 [features]
+const-generics = []
 core_hint_black_box = []
 default = ["std", "i128"]
 std = []

fuzz/Cargo.toml

@@ -10,7 +10,7 @@ cargo-fuzz = true
 
 [dependencies.subtle]
 path = ".."
-features = ["nightly"]
+features = ["nightly", "const-generics"]
 [dependencies.libfuzzer-sys]
 git = "https://github.com/rust-fuzz/libfuzzer-sys.git"
 

src/lib.rs

@@ -539,8 +539,10 @@ impl ConditionallySelectable for Choice {
     }
 }
 
+#[cfg(feature = "const-generics")]
 impl<T, const N: usize> ConditionallySelectable for [T; N]
-where T: ConditionallySelectable
+where
+    T: ConditionallySelectable,
 {
     #[inline]
     fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {