Fix use of no_std after rust-lang/RFC-1184

rust-lang/rfcs#1184

Author: Marwes

examples/no_std.rs

@@ -4,7 +4,7 @@
 // cfg-gating is a workaround for Cargo until https://github.com/rust-lang/cargo/issues/1570 lands.
 // Do not include it if you copy any code.
 
-#![cfg_attr(feature = "no_std", feature(lang_items, start, core, alloc, no_std))]
+#![cfg_attr(feature = "no_std", feature(lang_items, start, alloc, no_std))]
 #![cfg_attr(feature = "no_std", no_std)]
 
 #[cfg(not(feature = "no_std"))]
@@ -14,12 +14,11 @@ fn main() { }
 #[macro_use]
 extern crate mopa;
 
-#[cfg(feature = "no_std")]
-extern crate core;
 #[cfg(feature = "no_std")]
 extern crate alloc;
 
 #[cfg(feature = "no_std")]
+#[allow(dead_code)]
 mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item {
     trait Panic { fn panic(&self) { } }
 
@@ -43,5 +42,6 @@ mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item {
 
     #[lang = "stack_exhausted"] extern fn stack_exhausted() {}
     #[lang = "eh_personality"] extern fn eh_personality() {}
+    #[lang = "eh_unwind_resume"] extern fn eh_unwind_resume() {}
     #[lang = "panic_fmt"] extern fn panic_fmt() {}
 }

examples/no_std_or_alloc.rs

@@ -5,7 +5,7 @@
 // Do not include it if you copy any code.
 
 
-#![cfg_attr(feature = "no_std", feature(lang_items, start, core, libc, no_std))]
+#![cfg_attr(feature = "no_std", feature(lang_items, start, libc, no_std))]
 #![cfg_attr(feature = "no_std", no_std)]
 
 #[cfg(not(feature = "no_std"))]
@@ -15,17 +15,17 @@ fn main() { }
 #[macro_use]
 extern crate mopa;
 
-#[cfg(feature = "no_std")]
-extern crate core;
 #[cfg(feature = "no_std")]
 extern crate libc;
 
 #[cfg(feature = "no_std")]
+#[allow(dead_code)]
 mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item {
     trait Panic { fn panic(&self) { } }
 
     trait PanicAny: Panic + ::mopa::Any { }
 
+    #[allow(dead_code)]
     mopafy!(PanicAny, core = core);
 
     impl Panic for i32 { }
@@ -44,5 +44,6 @@ mod silly_wrapper_to_save_writing_the_whole_cfg_incantation_on_every_item {
 
     #[lang = "stack_exhausted"] extern fn stack_exhausted() {}
     #[lang = "eh_personality"] extern fn eh_personality() {}
+    #[lang = "eh_unwind_resume"] extern fn eh_unwind_resume() {}
     #[lang = "panic_fmt"] extern fn panic_fmt() {}
 }

src/lib.rs

@@ -132,13 +132,9 @@
 //! types across a variety of libraries. But the question of purpose and suitability is open, and I
 //! don’t have a really good example of such a use case here at present. TODO.
 
-#![cfg_attr(feature = "no_std", feature(core, no_std))]
+#![cfg_attr(feature = "no_std", feature(no_std))]
 #![cfg_attr(feature = "no_std", no_std)]
 
-#[cfg(feature = "no_std")]
-#[macro_use]
-extern crate core;
-
 #[cfg(all(test, feature = "no_std"))]
 extern crate std;
 
@@ -251,7 +247,7 @@ macro_rules! mopafy {
     };
 
     ($trait_:ident, core = $core:ident) => {
-        mopafy!($trait_(), core = $core, alloc = std);
+        mopafy!($trait_(), core = $core);
     };
 
     ($trait_:ident, core = $core:ident, alloc = $alloc:ident) => {
@@ -263,7 +259,7 @@ macro_rules! mopafy {
     };
 
     ($trait_:ident <$($args: ident),+>, core = $core:ident) => {
-        mopafy!($trait_($($args),*), core = $core, alloc = $alloc);
+        mopafy!($trait_($($args),*), core = $core);
     };
 
     ($trait_:ident <$($args: ident),+>, core = $core:ident, alloc = $alloc:ident) => {