From 011fa9107f405149d006a4208ffb8503214e82ce Mon Sep 17 00:00:00 2001
From: Dodo <kasper199914@gmail.com>
Date: Mon, 2 Mar 2020 21:05:14 +0100
Subject: [PATCH 1/3] const forget tests

---
 src/libcore/tests/lib.rs |  1 +
 src/libcore/tests/mem.rs | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs
index 991458db5b72b..cc341c939803e 100644
--- a/src/libcore/tests/lib.rs
+++ b/src/libcore/tests/lib.rs
@@ -40,6 +40,7 @@
 #![feature(never_type)]
 #![feature(unwrap_infallible)]
 #![feature(leading_trailing_ones)]
+#![feature(const_forget)]
 
 extern crate test;
 
diff --git a/src/libcore/tests/mem.rs b/src/libcore/tests/mem.rs
index 59588d97787b7..4841be5fc7107 100644
--- a/src/libcore/tests/mem.rs
+++ b/src/libcore/tests/mem.rs
@@ -129,3 +129,21 @@ fn test_discriminant_send_sync() {
     is_send_sync::<Discriminant<Regular>>();
     is_send_sync::<Discriminant<NotSendSync>>();
 }
+
+#[test]
+fn test_const_forget() {
+    const fn test_const_forget<T>(x: T) {
+        forget(x);
+    }
+
+    // Writing this function signature without const-forget
+    // triggers compiler errors:
+    // 1) That we use a non-const fn inside a const fn
+    // 2) without the forget, it complains about the destructor of Box
+    const fn const_forget_box<T>(mut x: Box<T>) {
+        forget(x);
+    }
+
+    const _: () = test_const_forget(0i32);
+    const _: () = test_const_forget(Vec::<Vec<Box<i32>>>::new());
+}
\ No newline at end of file

From 5f4af546d4fd19dd1238aaf2fd1026237b39916f Mon Sep 17 00:00:00 2001
From: Dodo <kasper199914@gmail.com>
Date: Mon, 2 Mar 2020 21:40:35 +0100
Subject: [PATCH 2/3] An enter as last character pleases tidy it seems

---
 src/libcore/tests/mem.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libcore/tests/mem.rs b/src/libcore/tests/mem.rs
index 4841be5fc7107..9ed2323e2873e 100644
--- a/src/libcore/tests/mem.rs
+++ b/src/libcore/tests/mem.rs
@@ -146,4 +146,4 @@ fn test_const_forget() {
 
     const _: () = test_const_forget(0i32);
     const _: () = test_const_forget(Vec::<Vec<Box<i32>>>::new());
-}
\ No newline at end of file
+}

From a674e1c88c632c237d7e56fbb6972b46c39a1fb0 Mon Sep 17 00:00:00 2001
From: Dodo <kasper199914@gmail.com>
Date: Mon, 2 Mar 2020 23:43:50 +0100
Subject: [PATCH 3/3] remove unused mut, restructure the test

---
 src/libcore/tests/mem.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/libcore/tests/mem.rs b/src/libcore/tests/mem.rs
index 9ed2323e2873e..8337ab103419f 100644
--- a/src/libcore/tests/mem.rs
+++ b/src/libcore/tests/mem.rs
@@ -132,18 +132,18 @@ fn test_discriminant_send_sync() {
 
 #[test]
 fn test_const_forget() {
-    const fn test_const_forget<T>(x: T) {
-        forget(x);
-    }
+    const _: () = forget(0i32);
+    const _: () = forget(Vec::<Vec<Box<i32>>>::new());
 
     // Writing this function signature without const-forget
     // triggers compiler errors:
     // 1) That we use a non-const fn inside a const fn
     // 2) without the forget, it complains about the destructor of Box
-    const fn const_forget_box<T>(mut x: Box<T>) {
+    const fn const_forget_box<T>(x: Box<T>) {
         forget(x);
     }
 
-    const _: () = test_const_forget(0i32);
-    const _: () = test_const_forget(Vec::<Vec<Box<i32>>>::new());
+    // Call the forget_box at runtime,
+    // as we can't const-construct a box yet.
+    const_forget_box(Box::new(0i32));
 }