From e4f250e405046713ba6fbcf481d0a88f26d25ae8 Mon Sep 17 00:00:00 2001
From: Alex Gaynor <alex.gaynor@gmail.com>
Date: Wed, 26 Jun 2019 07:50:30 -0400
Subject: [PATCH] Implement mem::{zeroed,uninitialized} in terms of
 MaybeUninit.

Refs #62061
---
 src/libcore/intrinsics.rs                        | 16 +++++++---------
 src/libcore/mem/mod.rs                           |  6 ++----
 src/librustc_codegen_llvm/intrinsic.rs           |  2 +-
 src/librustc_typeck/check/intrinsic.rs           |  1 -
 src/test/run-pass/intrinsics/intrinsic-uninit.rs | 13 -------------
 src/test/ui/init-unsafe.rs                       |  1 +
 src/test/ui/init-unsafe.stderr                   |  2 +-
 7 files changed, 12 insertions(+), 29 deletions(-)
 delete mode 100644 src/test/run-pass/intrinsics/intrinsic-uninit.rs

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index b30eff8baa9c8..7383b90bb4140 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -700,17 +700,15 @@ extern "rust-intrinsic" {
     /// which is unsafe unless `T` is `Copy`. Also, even if T is
     /// `Copy`, an all-zero value may not correspond to any legitimate
     /// state for the type in question.
+    #[unstable(feature = "core_intrinsics",
+               reason = "intrinsics are unlikely to ever be stabilized, instead \
+                         they should be used through stabilized interfaces \
+                         in the rest of the standard library",
+               issue = "0")]
+    #[rustc_deprecated(reason = "no longer used by rustc, will be removed - use MaybeUnint instead",
+                       since = "1.38.0")]
     pub fn init<T>() -> T;
 
-    /// Creates an uninitialized value.
-    ///
-    /// `uninit` is unsafe because there is no guarantee of what its
-    /// contents are. In particular its drop-flag may be set to any
-    /// state, which means it may claim either dropped or
-    /// undropped. In the general case one must use `ptr::write` to
-    /// initialize memory previous set to the result of `uninit`.
-    pub fn uninit<T>() -> T;
-
     /// Moves a value out of scope without running drop glue.
     pub fn forget<T: ?Sized>(_: T);
 
diff --git a/src/libcore/mem/mod.rs b/src/libcore/mem/mod.rs
index b31522db474b7..b62d81affddbd 100644
--- a/src/libcore/mem/mod.rs
+++ b/src/libcore/mem/mod.rs
@@ -450,8 +450,7 @@ pub const fn needs_drop<T>() -> bool {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn zeroed<T>() -> T {
-    intrinsics::panic_if_uninhabited::<T>();
-    intrinsics::init()
+    MaybeUninit::zeroed().assume_init()
 }
 
 /// Bypasses Rust's normal memory-initialization checks by pretending to
@@ -476,8 +475,7 @@ pub unsafe fn zeroed<T>() -> T {
 #[rustc_deprecated(since = "1.38.0", reason = "use `mem::MaybeUninit` instead")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn uninitialized<T>() -> T {
-    intrinsics::panic_if_uninhabited::<T>();
-    intrinsics::uninit()
+    MaybeUninit::uninit().assume_init()
 }
 
 /// Swaps the values at two mutable locations, without deinitializing either one.
diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index 7831c200114a5..69f8356f66920 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -234,7 +234,7 @@ impl IntrinsicCallMethods<'tcx> for Builder<'a, 'll, 'tcx> {
                 return;
             }
             // Effectively no-ops
-            "uninit" | "forget" => {
+            "forget" => {
                 return;
             }
             "needs_drop" => {
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index 9b1a891382209..82a736bf9c5f2 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -145,7 +145,6 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem) {
             "rustc_peek" => (1, vec![param(0)], param(0)),
             "panic_if_uninhabited" => (1, Vec::new(), tcx.mk_unit()),
             "init" => (1, Vec::new(), param(0)),
-            "uninit" => (1, Vec::new(), param(0)),
             "forget" => (1, vec![param(0)], tcx.mk_unit()),
             "transmute" => (2, vec![ param(0) ], param(1)),
             "move_val_init" => {
diff --git a/src/test/run-pass/intrinsics/intrinsic-uninit.rs b/src/test/run-pass/intrinsics/intrinsic-uninit.rs
deleted file mode 100644
index 9555efb639b50..0000000000000
--- a/src/test/run-pass/intrinsics/intrinsic-uninit.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-// run-pass
-// pretty-expanded FIXME #23616
-
-#![feature(intrinsics)]
-
-mod rusti {
-    extern "rust-intrinsic" {
-        pub fn uninit<T>() -> T;
-    }
-}
-pub fn main() {
-    let _a : isize = unsafe {rusti::uninit()};
-}
diff --git a/src/test/ui/init-unsafe.rs b/src/test/ui/init-unsafe.rs
index 92b21c4efa3a2..3d65cfc234092 100644
--- a/src/test/ui/init-unsafe.rs
+++ b/src/test/ui/init-unsafe.rs
@@ -1,3 +1,4 @@
+#![allow(deprecated)]
 #![feature(core_intrinsics)]
 
 use std::intrinsics::{init};
diff --git a/src/test/ui/init-unsafe.stderr b/src/test/ui/init-unsafe.stderr
index 857142dff64b7..e1126316af34e 100644
--- a/src/test/ui/init-unsafe.stderr
+++ b/src/test/ui/init-unsafe.stderr
@@ -1,5 +1,5 @@
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/init-unsafe.rs:7:17
+  --> $DIR/init-unsafe.rs:8:17
    |
 LL |     let stuff = init::<isize>();
    |                 ^^^^^^^^^^^^^^^ call to unsafe function