Automatically enable inclusive range support

This gets rid of the `rust_1_27` cargo feature.

Author: vks

Cargo.toml

@@ -12,6 +12,7 @@ Random number generators and other randomness functionality.
 """
 keywords = ["random", "rng"]
 categories = ["algorithms", "no-std"]
+build = "build.rs"
 
 [badges]
 travis-ci = { repository = "rust-lang-nursery/rand" }
@@ -25,7 +26,6 @@ alloc = ["rand_core/alloc"]  # enables Vec and Box support (without std)
 i128_support = [] # enables i128 and u128 support
 simd_support = [] # enables SIMD support
 serde1 = ["serde", "serde_derive", "rand_core/serde1"] # enables serialization for PRNGs
-rust_1_27 = ["i128_support"] # enables RangeInclusive, i128 and u128 support for Rust >= 1.27
 
 [workspace]
 members = ["rand_core", "rand_isaac"]
@@ -60,5 +60,8 @@ wasm-bindgen = { version = "0.2.12", optional = true }
 # deps yet, see: https://github.com/rust-lang/cargo/issues/1596
 bincode = "1.0"
 
+[build-dependencies]
+rustc_version = "0.2"
+
 [package.metadata.docs.rs]
 all-features = true

src/distributions/uniform.rs

@@ -276,7 +276,7 @@ impl<X: SampleUniform> From<::core::ops::Range<X>> for Uniform<X> {
     }
 }
 
-#[cfg(feature = "rust_1_27")]
+#[cfg(rust_1_27)]
 impl<X: SampleUniform> From<::core::ops::RangeInclusive<X>> for Uniform<X> {
     fn from(r: ::core::ops::RangeInclusive<X>) -> Uniform<X> {
         Uniform::new_inclusive(r.start(), r.end())
@@ -1068,7 +1068,7 @@ mod tests {
         assert_eq!(r.inner.scale, 5.0);
     }
 
-    #[cfg(feature = "rust_1_27")]
+    #[cfg(rust_1_27)]
     #[test]
     fn test_uniform_from_std_range_inclusive() {
         let r = Uniform::from(2u32..=6);