Const-stabilize `Vec::new`.
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 370e5cf..9e6ed92 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -117,7 +117,7 @@
#![feature(allocator_internals)]
#![feature(on_unimplemented)]
#![feature(rustc_const_unstable)]
-#![feature(const_vec_new)]
+#![cfg_attr(bootstrap, feature(const_vec_new))]
#![feature(slice_partition_dedup)]
#![feature(maybe_uninit_extra, maybe_uninit_slice)]
#![feature(alloc_layout_extra)]
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index cf025ee..ee75fc2 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -113,13 +113,38 @@
}
impl<T> RawVec<T, Global> {
+ /// HACK(Centril): This exists because `#[unstable]` `const fn`s needn't conform
+ /// to `min_const_fn` and so they cannot be called in `min_const_fn`s either.
+ ///
+ /// If you change `RawVec<T>::new` or dependencies, please take care to not
+ /// introduce anything that would truly violate `min_const_fn`.
+ ///
+ /// NOTE: We could avoid this hack and check conformance with some
+ /// `#[rustc_force_min_const_fn]` attribute which requires conformance
+ /// with `min_const_fn` but does not necessarily allow calling it in
+ /// `stable(...) const fn` / user code not enabling `foo` when
+ /// `#[rustc_const_unstable(feature = "foo", ..)]` is present.
+ pub const NEW: Self = Self::new();
+
/// Creates the biggest possible `RawVec` (on the system heap)
/// without allocating. If `T` has positive size, then this makes a
/// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
/// `RawVec` with capacity `usize::MAX`. Useful for implementing
/// delayed allocation.
pub const fn new() -> Self {
- Self::new_in(Global)
+ // FIXME(Centril): Reintegrate this with `fn new_in` when we can.
+
+ // `!0` is `usize::MAX`. This branch should be stripped at compile time.
+ // FIXME(mark-i-m): use this line when `if`s are allowed in `const`:
+ //let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
+
+ // `Unique::empty()` doubles as "unallocated" and "zero-sized allocation".
+ RawVec {
+ ptr: Unique::empty(),
+ // FIXME(mark-i-m): use `cap` when ifs are allowed in const
+ cap: [0, !0][(mem::size_of::<T>() == 0) as usize],
+ a: Global,
+ }
}
/// Creates a `RawVec` (on the system heap) with exactly the
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index c513658..405969a 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -314,10 +314,10 @@
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- #[rustc_const_unstable(feature = "const_vec_new")]
+ #[cfg_attr(bootstrap, rustc_const_unstable(feature = "const_vec_new"))]
pub const fn new() -> Vec<T> {
Vec {
- buf: RawVec::new(),
+ buf: RawVec::NEW,
len: 0,
}
}
diff --git a/src/test/ui/collections-const-new.rs b/src/test/ui/collections-const-new.rs
index e01b0df..15c5c65 100644
--- a/src/test/ui/collections-const-new.rs
+++ b/src/test/ui/collections-const-new.rs
@@ -1,15 +1,13 @@
// run-pass
-#![allow(dead_code)]
// Test several functions can be used for constants
// 1. Vec::new()
// 2. String::new()
-#![feature(const_vec_new)]
#![feature(const_string_new)]
const MY_VEC: Vec<usize> = Vec::new();
const MY_STRING: String = String::new();
-pub fn main() {}
+fn main() {}
diff --git a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
index 5fb9253..8b17f68 100644
--- a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
+++ b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.rs
@@ -14,8 +14,9 @@
impl Foo<u32> for () {
const X: u32 = 42;
}
+
impl Foo<Vec<u32>> for String {
- const X: Vec<u32> = Vec::new(); //~ ERROR not yet stable as a const fn
+ const X: Vec<u32> = Vec::new();
}
impl Bar<u32, ()> for () {}
diff --git a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
index c56ebf6..5bc7b70 100644
--- a/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
+++ b/src/test/ui/consts/miri_unleashed/feature-gate-unleash_the_miri_inside_of_you.stderr
@@ -4,13 +4,5 @@
LL | const F: u32 = (U::X, 42).1;
| ^^^^^^^^^^ constants cannot evaluate destructors
-error: `std::vec::Vec::<T>::new` is not yet stable as a const fn
- --> $DIR/feature-gate-unleash_the_miri_inside_of_you.rs:18:25
- |
-LL | const X: Vec<u32> = Vec::new();
- | ^^^^^^^^^^
- |
- = help: add `#![feature(const_vec_new)]` to the crate attributes to enable
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
