Require opt-in for promoting const fn calls

Author: oli-obk

src/liballoc/lib.rs

@@ -103,6 +103,7 @@
 #![feature(optin_builtin_traits)]
 #![feature(pattern)]
 #![feature(pin)]
+#![feature(promotable_const_fn)]
 #![feature(ptr_internals)]
 #![feature(ptr_offset_from)]
 #![feature(repr_transparent)]

src/liballoc/raw_vec.rs

@@ -56,6 +56,7 @@ pub struct RawVec<T, A: Alloc = Global> {
 impl<T, A: Alloc> RawVec<T, A> {
     /// Like `new` but parameterized over the choice of allocator for
     /// the returned RawVec.
+    #[promotable_const_fn]
     pub const fn new_in(a: A) -> Self {
         // !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`
@@ -123,6 +124,7 @@ impl<T> RawVec<T, Global> {
     /// RawVec with capacity 0. If T has 0 size, then it makes a
     /// RawVec with capacity `usize::MAX`. Useful for implementing
     /// delayed allocation.
+    #[promotable_const_fn]
     pub const fn new() -> Self {
         Self::new_in(Global)
     }

src/liballoc/string.rs

@@ -381,6 +381,7 @@ impl String {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_string_new")]
+    #[promotable_const_fn]
     pub const fn new() -> String {
         String { vec: Vec::new() }
     }

src/liballoc/vec.rs

@@ -320,6 +320,7 @@ impl<T> Vec<T> {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_vec_new")]
+    #[promotable_const_fn]
     pub const fn new() -> Vec<T> {
         Vec {
             buf: RawVec::new(),

src/libcore/any.rs

@@ -458,6 +458,7 @@ impl TypeId {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature="const_type_id")]
+    #[promotable_const_fn]
     pub const fn of<T: ?Sized + 'static>() -> TypeId {
         TypeId {
             t: unsafe { intrinsics::type_id::<T>() },

src/libcore/cell.rs

@@ -374,6 +374,7 @@ impl<T> Cell<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
+    #[promotable_const_fn]
     pub const fn new(value: T) -> Cell<T> {
         Cell {
             value: UnsafeCell::new(value),
@@ -588,6 +589,7 @@ impl<T> RefCell<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
+    #[promotable_const_fn]
     pub const fn new(value: T) -> RefCell<T> {
         RefCell {
             value: UnsafeCell::new(value),
@@ -1304,6 +1306,7 @@ impl<T> UnsafeCell<T> {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
+    #[promotable_const_fn]
     pub const fn new(value: T) -> UnsafeCell<T> {
         UnsafeCell { value: value }
     }

src/libcore/lib.rs

@@ -99,6 +99,7 @@
 #![feature(on_unimplemented)]
 #![feature(optin_builtin_traits)]
 #![feature(prelude_import)]
+#![feature(promotable_const_fn)]
 #![feature(repr_simd, platform_intrinsics)]
 #![feature(repr_transparent)]
 #![feature(rustc_attrs)]

src/libcore/mem.rs

@@ -314,6 +314,7 @@ pub fn forget<T>(t: T) {
 /// [alignment]: ./fn.align_of.html
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[promotable_const_fn]
 pub const fn size_of<T>() -> usize {
     unsafe { intrinsics::size_of::<T>() }
 }
@@ -405,6 +406,7 @@ pub fn min_align_of_val<T: ?Sized>(val: &T) -> usize {
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[promotable_const_fn]
 pub const fn align_of<T>() -> usize {
     unsafe { intrinsics::min_align_of::<T>() }
 }
@@ -966,6 +968,7 @@ impl<T> ManuallyDrop<T> {
     #[stable(feature = "manually_drop", since = "1.20.0")]
     #[rustc_const_unstable(feature = "const_manually_drop_new")]
     #[inline]
+    #[promotable_const_fn]
     pub const fn new(value: T) -> ManuallyDrop<T> {
         ManuallyDrop { value: value }
     }

src/libcore/num/mod.rs

@@ -200,6 +200,7 @@ $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[promotable_const_fn]
             pub const fn min_value() -> Self {
                 !0 ^ ((!0 as $UnsignedT) >> 1) as Self
             }
@@ -218,6 +219,7 @@ $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[promotable_const_fn]
             pub const fn max_value() -> Self {
                 !Self::min_value()
             }
@@ -2103,6 +2105,7 @@ Basic usage:
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[promotable_const_fn]
             pub const fn min_value() -> Self { 0 }
         }
 
@@ -2119,6 +2122,7 @@ stringify!($MaxV), ");", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[promotable_const_fn]
             pub const fn max_value() -> Self { !0 }
         }
 

src/libcore/num/wrapping.rs

@@ -344,6 +344,7 @@ assert_eq!(<Wrapping<", stringify!($t), ">>::min_value(), ",
 ```"),
                 #[unstable(feature = "wrapping_int_impl", issue = "32463")]
                 #[inline]
+                #[promotable_const_fn]
                 pub const fn min_value() -> Self {
                     Wrapping(<$t>::min_value())
                 }
@@ -365,6 +366,7 @@ assert_eq!(<Wrapping<", stringify!($t), ">>::max_value(), ",
 ```"),
                 #[unstable(feature = "wrapping_int_impl", issue = "32463")]
                 #[inline]
+                #[promotable_const_fn]
                 pub const fn max_value() -> Self {
                     Wrapping(<$t>::max_value())
                 }