From 97f200533058ee40b1b4ba01a6996a994ce8c171 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 17:13:03 +0100
Subject: [PATCH 01/12] Add unstable cfg_if! macro to libcore

---
 src/libcore/macros.rs       | 83 +++++++++++++++++++++++++++++++++++++
 src/libcore/tests/cfg_if.rs | 52 +++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 src/libcore/tests/cfg_if.rs

diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index ad8ce1af1f6a1..3d45ed8b017e4 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -635,6 +635,89 @@ macro_rules! uninitialized_array {
     });
 }
 
+/// A macro for defining `#[cfg]` if-else statements.
+///
+/// The macro provided by this crate, `cfg_if`, is similar to the `if/elif` C
+/// preprocessor macro by allowing definition of a cascade of `#[cfg]` cases,
+/// emitting the implementation which matches first.
+///
+/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code
+/// without having to rewrite each clause multiple times.
+///
+/// # Example
+///
+/// ```
+/// #[macro_use]
+/// extern crate cfg_if;
+///
+/// cfg_if! {
+///     if #[cfg(unix)] {
+///         fn foo() { /* unix specific functionality */ }
+///     } else if #[cfg(target_pointer_width = "32")] {
+///         fn foo() { /* non-unix, 32-bit functionality */ }
+///     } else {
+///         fn foo() { /* fallback implementation */ }
+///     }
+/// }
+///
+/// # fn main() {}
+/// ```
+#[macro_export(local_inner_macros)]
+#[unstable(feature = "cfg_if", issue = "59442")]
+macro_rules! cfg_if {
+    // match if/else chains with a final `else`
+    ($(
+        if #[cfg($($meta:meta),*)] { $($it:item)* }
+    ) else * else {
+        $($it2:item)*
+    }) => {
+        cfg_if! {
+            @__items
+            () ;
+            $( ( ($($meta),*) ($($it)*) ), )*
+            ( () ($($it2)*) ),
+        }
+    };
+
+    // match if/else chains lacking a final `else`
+    (
+        if #[cfg($($i_met:meta),*)] { $($i_it:item)* }
+        $(
+            else if #[cfg($($e_met:meta),*)] { $($e_it:item)* }
+        )*
+    ) => {
+        cfg_if! {
+            @__items
+            () ;
+            ( ($($i_met),*) ($($i_it)*) ),
+            $( ( ($($e_met),*) ($($e_it)*) ), )*
+            ( () () ),
+        }
+    };
+
+    // Internal and recursive macro to emit all the items
+    //
+    // Collects all the negated cfgs in a list at the beginning and after the
+    // semicolon is all the remaining items
+    (@__items ($($not:meta,)*) ; ) => {};
+    (@__items ($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
+        // Emit all items within one block, applying an approprate #[cfg]. The
+        // #[cfg] will require all `$m` matchers specified and must also negate
+        // all previous matchers.
+        cfg_if! { @__apply cfg(all($($m,)* not(any($($not),*)))), $($it)* }
+
+        // Recurse to emit all other items in `$rest`, and when we do so add all
+        // our `$m` matchers to the list of `$not` matchers as future emissions
+        // will have to negate everything we just matched as well.
+        cfg_if! { @__items ($($not,)* $($m,)*) ; $($rest)* }
+    };
+
+    // Internal macro to Apply a cfg attribute to a list of items
+    (@__apply $m:meta, $($it:item)*) => {
+        $(#[$m] $it)*
+    };
+}
+
 /// Built-in macros to the compiler itself.
 ///
 /// These macros do not have any corresponding definition with a `macro_rules!`
diff --git a/src/libcore/tests/cfg_if.rs b/src/libcore/tests/cfg_if.rs
new file mode 100644
index 0000000000000..2e9784d8543d0
--- /dev/null
+++ b/src/libcore/tests/cfg_if.rs
@@ -0,0 +1,52 @@
+#![feature(cfg_if)]
+
+cfg_if! {
+    if #[cfg(test)] {
+        use core::option::Option as Option2;
+        fn works1() -> Option2<u32> { Some(1) }
+    } else {
+        fn works1() -> Option<u32> { None }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works2() -> bool { false }
+    } else if #[cfg(test)] {
+        fn works2() -> bool { true }
+    } else {
+        fn works2() -> bool { false }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works3() -> bool { false }
+    } else {
+        fn works3() -> bool { true }
+    }
+}
+
+cfg_if! {
+    if #[cfg(test)] {
+        use core::option::Option as Option3;
+        fn works4() -> Option3<u32> { Some(1) }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works5() -> bool { false }
+    } else if #[cfg(test)] {
+        fn works5() -> bool { true }
+    }
+}
+
+#[test]
+fn it_works() {
+    assert!(works1().is_some());
+    assert!(works2());
+    assert!(works3());
+    assert!(works4().is_some());
+    assert!(works5());
+}

From c0aabcf038c541660ae2d7e5ada96c2fa240ea4f Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:31:37 +0100
Subject: [PATCH 02/12] Remove cfg_if macro from libstd

---
 src/libstd/macros.rs | 36 ------------------------------------
 1 file changed, 36 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index d5dc5f7c4f0df..e00e234997548 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -943,39 +943,3 @@ mod builtin {
         ($cond:expr, $($arg:tt)+) => ({ /* compiler built-in */ });
     }
 }
-
-/// A macro for defining `#[cfg]` if-else statements.
-///
-/// This is similar to the `if/elif` C preprocessor macro by allowing definition
-/// of a cascade of `#[cfg]` cases, emitting the implementation which matches
-/// first.
-///
-/// This allows you to conveniently provide a long list `#[cfg]`'d blocks of code
-/// without having to rewrite each clause multiple times.
-macro_rules! cfg_if {
-    ($(
-        if #[cfg($($meta:meta),*)] { $($it:item)* }
-    ) else * else {
-        $($it2:item)*
-    }) => {
-        __cfg_if_items! {
-            () ;
-            $( ( ($($meta),*) ($($it)*) ), )*
-            ( () ($($it2)*) ),
-        }
-    }
-}
-
-macro_rules! __cfg_if_items {
-    (($($not:meta,)*) ; ) => {};
-    (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
-        __cfg_if_apply! { cfg(all(not(any($($not),*)), $($m,)*)), $($it)* }
-        __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
-    }
-}
-
-macro_rules! __cfg_if_apply {
-    ($m:meta, $($it:item)*) => {
-        $(#[$m] $it)*
-    }
-}

From 3e9d356da57f2bc425c5cd0df93494d9ae302404 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:34:30 +0100
Subject: [PATCH 03/12] Test that cfg_if from prelude can be overriden

---
 src/libcore/tests/cfg_if_override.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 src/libcore/tests/cfg_if_override.rs

diff --git a/src/libcore/tests/cfg_if_override.rs b/src/libcore/tests/cfg_if_override.rs
new file mode 100644
index 0000000000000..b8cd205d3205b
--- /dev/null
+++ b/src/libcore/tests/cfg_if_override.rs
@@ -0,0 +1,16 @@
+#![feature(cfg_if)]
+
+macro_rules! cfg_if {
+    (()) => {
+        mod foo {
+            fn foo() {}
+        }
+    }
+}
+
+cfg_if!{}
+
+#[test]
+fn it_works() {
+    foo::foo();
+}

From 52bd6ad7199272b4eb71ce94f04aac0a114c456c Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:38:52 +0100
Subject: [PATCH 04/12] Add test that overrides cfg_if with the one from
 crates.io

---
 src/libcore/Cargo.toml                      |  1 +
 src/libcore/tests/cfg_if_override.rs        |  2 +
 src/libcore/tests/cfg_if_stable_override.rs | 55 +++++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 src/libcore/tests/cfg_if_stable_override.rs

diff --git a/src/libcore/Cargo.toml b/src/libcore/Cargo.toml
index fa2ab11243b6c..6865525e0c89f 100644
--- a/src/libcore/Cargo.toml
+++ b/src/libcore/Cargo.toml
@@ -21,6 +21,7 @@ path = "../libcore/benches/lib.rs"
 
 [dev-dependencies]
 rand = "0.6"
+cfg_if = "1.0"
 
 [features]
 # Make panics and failed asserts immediately abort without formatting any message
diff --git a/src/libcore/tests/cfg_if_override.rs b/src/libcore/tests/cfg_if_override.rs
index b8cd205d3205b..fc1cc6156a7e9 100644
--- a/src/libcore/tests/cfg_if_override.rs
+++ b/src/libcore/tests/cfg_if_override.rs
@@ -1,3 +1,5 @@
+//! Test that overriding cfg_if with our own cfg_if macro does not break
+//! anything.
 #![feature(cfg_if)]
 
 macro_rules! cfg_if {
diff --git a/src/libcore/tests/cfg_if_stable_override.rs b/src/libcore/tests/cfg_if_stable_override.rs
new file mode 100644
index 0000000000000..2718b9cab9fa1
--- /dev/null
+++ b/src/libcore/tests/cfg_if_stable_override.rs
@@ -0,0 +1,55 @@
+//! Test that using cfg_if from the cfg_if crate does not break anything.
+
+#[macro_use(cfg_if)]
+extern crate cfg_if;
+
+cfg_if! {
+    if #[cfg(test)] {
+        use core::option::Option as Option2;
+        fn works1() -> Option2<u32> { Some(1) }
+    } else {
+        fn works1() -> Option<u32> { None }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works2() -> bool { false }
+    } else if #[cfg(test)] {
+        fn works2() -> bool { true }
+    } else {
+        fn works2() -> bool { false }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works3() -> bool { false }
+    } else {
+        fn works3() -> bool { true }
+    }
+}
+
+cfg_if! {
+    if #[cfg(test)] {
+        use core::option::Option as Option3;
+        fn works4() -> Option3<u32> { Some(1) }
+    }
+}
+
+cfg_if! {
+    if #[cfg(foo)] {
+        fn works5() -> bool { false }
+    } else if #[cfg(test)] {
+        fn works5() -> bool { true }
+    }
+}
+
+#[test]
+fn it_works() {
+    assert!(works1().is_some());
+    assert!(works2());
+    assert!(works3());
+    assert!(works4().is_some());
+    assert!(works5());
+}

From f35f2dfe80ea1350376d2f527fefd1bf538a5b90 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:47:12 +0100
Subject: [PATCH 05/12] Enable cfg_if feature for libstd

---
 src/libstd/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 296c4c887274e..1710ae09b78d7 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -241,6 +241,7 @@
 #![feature(bind_by_move_pattern_guards)]
 #![feature(box_syntax)]
 #![feature(c_variadic)]
+#![feature(cfg_if)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_thread_local)]
 #![feature(char_error_internals)]

From 72eed28c8d15e75a6c0dba144c2e486e227d06eb Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:54:45 +0100
Subject: [PATCH 06/12] cfg_if doc-example should use the macro from libcore

---
 src/libcore/macros.rs | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 3d45ed8b017e4..e45c4afb55fd9 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -647,9 +647,6 @@ macro_rules! uninitialized_array {
 /// # Example
 ///
 /// ```
-/// #[macro_use]
-/// extern crate cfg_if;
-///
 /// cfg_if! {
 ///     if #[cfg(unix)] {
 ///         fn foo() { /* unix specific functionality */ }

From f6fbf937f375565df3de7090e352d0beb6d738bc Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:54:58 +0100
Subject: [PATCH 07/12] Remove unnecessary feature(cfg_if)

---
 src/libcore/tests/cfg_if_override.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/libcore/tests/cfg_if_override.rs b/src/libcore/tests/cfg_if_override.rs
index fc1cc6156a7e9..16471ec91b1ec 100644
--- a/src/libcore/tests/cfg_if_override.rs
+++ b/src/libcore/tests/cfg_if_override.rs
@@ -1,6 +1,5 @@
 //! Test that overriding cfg_if with our own cfg_if macro does not break
 //! anything.
-#![feature(cfg_if)]
 
 macro_rules! cfg_if {
     (()) => {

From 881b5922e10d4edbdfca52ca909fad5e43742cad Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 19:56:11 +0100
Subject: [PATCH 08/12] Fix typo in name of the cfg-if dev-dependency

---
 src/libcore/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcore/Cargo.toml b/src/libcore/Cargo.toml
index 6865525e0c89f..1790d61558494 100644
--- a/src/libcore/Cargo.toml
+++ b/src/libcore/Cargo.toml
@@ -21,7 +21,7 @@ path = "../libcore/benches/lib.rs"
 
 [dev-dependencies]
 rand = "0.6"
-cfg_if = "1.0"
+cfg-if = "1.0"
 
 [features]
 # Make panics and failed asserts immediately abort without formatting any message

From 168229b1177423610dd69d7d13a10d0ae3eebdd3 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 20:09:16 +0100
Subject: [PATCH 09/12] Re-export cfg_if macro from libstd and test

---
 src/libstd/lib.rs          |  4 ++++
 src/libstd/tests/cfg_if.rs | 14 ++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 src/libstd/tests/cfg_if.rs

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 1710ae09b78d7..dce40160fadac 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -327,6 +327,10 @@ pub use core::{assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::{unreachable, unimplemented, write, writeln, r#try, todo};
 
+#[unstable(feature = "cfg_if", issue = "59442")]
+pub use core::cfg_if;
+
+
 #[allow(unused_imports)] // macros from `alloc` are not used on all platforms
 #[macro_use]
 extern crate alloc as alloc_crate;
diff --git a/src/libstd/tests/cfg_if.rs b/src/libstd/tests/cfg_if.rs
new file mode 100644
index 0000000000000..cd84202767d9a
--- /dev/null
+++ b/src/libstd/tests/cfg_if.rs
@@ -0,0 +1,14 @@
+pub use std::cfg_if;
+
+cfg_if! {
+    if #[cfg(test)] {
+        fn foo() -> bool { true }
+    } else {
+        fn foo() -> bool { false }
+    }
+}
+
+#[test]
+fn cfg_if_test {
+    assert!(foo());
+}

From f915ae4a91ab9e7d44110d7343bf9cf85ffce8ef Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Tue, 26 Mar 2019 22:31:06 +0100
Subject: [PATCH 10/12] Choose right cfg-if version number

---
 src/libcore/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcore/Cargo.toml b/src/libcore/Cargo.toml
index 1790d61558494..8508fa4aa3e57 100644
--- a/src/libcore/Cargo.toml
+++ b/src/libcore/Cargo.toml
@@ -21,7 +21,7 @@ path = "../libcore/benches/lib.rs"
 
 [dev-dependencies]
 rand = "0.6"
-cfg-if = "1.0"
+cfg-if = "0.1"
 
 [features]
 # Make panics and failed asserts immediately abort without formatting any message

From 165882ca0e2a6c60ec11bc2ee7add946c8918b75 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Thu, 28 Mar 2019 10:42:38 +0100
Subject: [PATCH 11/12] Update Cargo.lock

---
 Cargo.lock | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 73adb762e485b..279f1f5e31a1c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -521,6 +521,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "core"
 version = "0.0.0"
 dependencies = [
+ "cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2074,7 +2075,7 @@ name = "rand_chacha"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -2096,7 +2097,7 @@ name = "rand_hc"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2121,7 +2122,7 @@ name = "rand_xorshift"
 version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "rand_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

From 98e146185d1f12094b42c66d9c5211656b6bb0f8 Mon Sep 17 00:00:00 2001
From: gnzlbg <gonzalobg88@gmail.com>
Date: Fri, 29 Mar 2019 12:21:40 +0100
Subject: [PATCH 12/12] fix build

---
 src/libcore/macros.rs      | 1 +
 src/libstd/tests/cfg_if.rs | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index e45c4afb55fd9..9cfa70f91954a 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -647,6 +647,7 @@ macro_rules! uninitialized_array {
 /// # Example
 ///
 /// ```
+/// # #![feature(cfg_if)]
 /// cfg_if! {
 ///     if #[cfg(unix)] {
 ///         fn foo() { /* unix specific functionality */ }
diff --git a/src/libstd/tests/cfg_if.rs b/src/libstd/tests/cfg_if.rs
index cd84202767d9a..3ecfadba8d3c9 100644
--- a/src/libstd/tests/cfg_if.rs
+++ b/src/libstd/tests/cfg_if.rs
@@ -1,3 +1,4 @@
+#![feature(cfg_if)]
 pub use std::cfg_if;
 
 cfg_if! {
@@ -9,6 +10,6 @@ cfg_if! {
 }
 
 #[test]
-fn cfg_if_test {
+fn cfg_if_test() {
     assert!(foo());
 }