Simplify no_std logic a bit

phf/src/lib.rs

@@ -8,17 +8,12 @@
 #![cfg_attr(feature = "core", feature(no_std))]
 #![cfg_attr(feature = "core", no_std)]
 
+#[cfg(not(feature = "core"))]
+extern crate std as core;
+
 extern crate debug_builders;
 extern crate phf_shared;
 
-#[cfg(feature = "core")]
-mod std {
-    pub use core::{borrow, fmt, iter, option, ops, slice};
-    pub mod prelude {
-        pub use core::prelude as v1;
-    }
-}
-
 pub use phf_shared::PhfHash;
 #[doc(inline)]
 pub use map::Map;

phf/src/map.rs

@@ -1,10 +1,10 @@
 //! An immutable map constructed at compile time.
 use debug_builders::DebugMap;
-use std::borrow::Borrow;
-use std::ops::Index;
-use std::slice;
-use std::fmt;
-use std::iter::IntoIterator;
+use core::borrow::Borrow;
+use core::ops::Index;
+use core::slice;
+use core::fmt;
+use core::iter::IntoIterator;
 use PhfHash;
 use phf_shared;
 

phf/src/ordered_map.rs

@@ -1,10 +1,10 @@
 //! An order-preserving immutable map constructed at compile time.
 use debug_builders::DebugMap;
-use std::borrow::Borrow;
-use std::iter::IntoIterator;
-use std::ops::Index;
-use std::fmt;
-use std::slice;
+use core::borrow::Borrow;
+use core::iter::IntoIterator;
+use core::ops::Index;
+use core::fmt;
+use core::slice;
 
 use PhfHash;
 use phf_shared;

phf/src/ordered_set.rs

@@ -1,8 +1,8 @@
 //! An order-preserving immutable set constructed at compile time.
 use debug_builders::DebugSet;
-use std::borrow::Borrow;
-use std::iter::IntoIterator;
-use std::fmt;
+use core::borrow::Borrow;
+use core::iter::IntoIterator;
+use core::fmt;
 use ordered_map;
 use {PhfHash, OrderedMap};
 

phf/src/set.rs

@@ -1,8 +1,8 @@
 //! An immutable set constructed at compile time.
 use debug_builders::DebugSet;
-use std::borrow::Borrow;
-use std::iter::IntoIterator;
-use std::fmt;
+use core::borrow::Borrow;
+use core::iter::IntoIterator;
+use core::fmt;
 
 use PhfHash;
 use map;

phf_shared/src/lib.rs

@@ -1,13 +1,10 @@
 #![doc(html_root_url="http://sfackler.github.io/rust-phf/doc/v0.7.5")]
 #![cfg_attr(feature = "core", feature(no_std, core_slice_ext, core_str_ext))]
 #![cfg_attr(feature = "core", no_std)]
+#[cfg(not(feature = "core"))]
+extern crate std as core;
 
-#[cfg(feature = "core")]
-mod std {
-    pub use core::{slice, str, hash};
-}
-
-use std::hash::{Hasher, Hash, SipHasher};
+use core::hash::{Hasher, Hash, SipHasher};
 
 #[inline]
 pub fn displace(f1: u32, f2: u32, d1: u32, d2: u32) -> u32 {