Rollup merge of rust-lang#69899 - ecstatic-morse:const-idx-methods, r=oli-obk

Make methods declared by `newtype_index` macro `const`

Crates that use the macro to define an `Idx` type need to enable `#![feature(const_if_match, const_panic)]`.

Author: Centril

src/librustc/hir/map/mod.rs

@@ -346,7 +346,7 @@ impl<'hir> Map<'hir> {
     }
 
     fn get_entry(&self, id: HirId) -> Entry<'hir> {
-        if id.local_id == ItemLocalId::from_u32_const(0) {
+        if id.local_id == ItemLocalId::from_u32(0) {
             let owner = self.tcx.hir_owner(id.owner_def_id());
             Entry { parent: owner.parent, node: owner.node }
         } else {

src/librustc/lib.rs

@@ -26,6 +26,9 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
+#![feature(const_if_match)]
+#![feature(const_fn)]
+#![feature(const_panic)]
 #![feature(const_transmute)]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]

src/librustc/ty/mod.rs

@@ -1700,7 +1700,7 @@ rustc_index::newtype_index! {
 }
 
 impl UniverseIndex {
-    pub const ROOT: UniverseIndex = UniverseIndex::from_u32_const(0);
+    pub const ROOT: UniverseIndex = UniverseIndex::from_u32(0);
 
     /// Returns the "next" universe index in order -- this new index
     /// is considered to extend all previous universes. This

src/librustc_ast/lib.rs

@@ -7,7 +7,9 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/", test(attr(deny(warnings))))]
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
+#![feature(const_if_match)]
 #![feature(const_fn)] // For the `transmute` in `P::new`
+#![feature(const_panic)]
 #![feature(const_transmute)]
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]

src/librustc_ast/node_id.rs

@@ -12,7 +12,7 @@ rustc_index::newtype_index! {
 rustc_data_structures::define_id_collections!(NodeMap, NodeSet, NodeId);
 
 /// `NodeId` used to represent the root of the crate.
-pub const CRATE_NODE_ID: NodeId = NodeId::from_u32_const(0);
+pub const CRATE_NODE_ID: NodeId = NodeId::from_u32(0);
 
 /// When parsing and doing expansions, we initially give all AST nodes this AST
 /// node value. Then later, in the renumber pass, we renumber them to have

src/librustc_hir/hir_id.rs

@@ -71,7 +71,7 @@ rustc_data_structures::impl_stable_hash_via_hash!(ItemLocalId);
 
 /// The `HirId` corresponding to `CRATE_NODE_ID` and `CRATE_DEF_INDEX`.
 pub const CRATE_HIR_ID: HirId =
-    HirId { owner: CRATE_DEF_INDEX, local_id: ItemLocalId::from_u32_const(0) };
+    HirId { owner: CRATE_DEF_INDEX, local_id: ItemLocalId::from_u32(0) };
 
 pub const DUMMY_HIR_ID: HirId = HirId { owner: CRATE_DEF_INDEX, local_id: DUMMY_ITEM_LOCAL_ID };
 

src/librustc_hir/lib.rs

@@ -3,7 +3,9 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 
 #![feature(crate_visibility_modifier)]
+#![feature(const_if_match)]
 #![feature(const_fn)] // For the unsizing cast on `&[]`
+#![feature(const_panic)]
 #![feature(in_band_lifetimes)]
 #![feature(specialization)]
 #![recursion_limit = "256"]

src/librustc_index/lib.rs

@@ -1,4 +1,7 @@
 #![feature(allow_internal_unstable)]
+#![feature(const_if_match)]
+#![feature(const_fn)]
+#![feature(const_panic)]
 #![feature(unboxed_closures)]
 #![feature(test)]
 #![feature(fn_traits)]

src/librustc_index/vec.rs

@@ -120,62 +120,44 @@ macro_rules! newtype_index {
         impl $type {
             $v const MAX_AS_U32: u32 = $max;
 
-            $v const MAX: Self = Self::from_u32_const($max);
+            $v const MAX: Self = Self::from_u32($max);
 
             #[inline]
-            $v fn from_usize(value: usize) -> Self {
+            $v const fn from_usize(value: usize) -> Self {
                 assert!(value <= ($max as usize));
                 unsafe {
                     Self::from_u32_unchecked(value as u32)
                 }
             }
 
             #[inline]
-            $v fn from_u32(value: u32) -> Self {
+            $v const fn from_u32(value: u32) -> Self {
                 assert!(value <= $max);
                 unsafe {
                     Self::from_u32_unchecked(value)
                 }
             }
 
-            /// Hacky variant of `from_u32` for use in constants.
-            /// This version checks the "max" constraint by using an
-            /// invalid array dereference.
-            #[inline]
-            $v const fn from_u32_const(value: u32) -> Self {
-                // This will fail at const eval time unless `value <=
-                // max` is true (in which case we get the index 0).
-                // It will also fail at runtime, of course, but in a
-                // kind of wacky way.
-                let _ = ["out of range value used"][
-                    !(value <= $max) as usize
-                ];
-
-                unsafe {
-                    Self { private: value }
-                }
-            }
-
             #[inline]
             $v const unsafe fn from_u32_unchecked(value: u32) -> Self {
                 Self { private: value }
             }
 
             /// Extracts the value of this index as an integer.
             #[inline]
-            $v fn index(self) -> usize {
+            $v const fn index(self) -> usize {
                 self.as_usize()
             }
 
             /// Extracts the value of this index as a `u32`.
             #[inline]
-            $v fn as_u32(self) -> u32 {
+            $v const fn as_u32(self) -> u32 {
                 self.private
             }
 
             /// Extracts the value of this index as a `usize`.
             #[inline]
-            $v fn as_usize(self) -> usize {
+            $v const fn as_usize(self) -> usize {
                 self.as_u32() as usize
             }
         }
@@ -500,7 +482,7 @@ macro_rules! newtype_index {
                    const $name:ident = $constant:expr,
                    $($tokens:tt)*) => (
         $(#[doc = $doc])*
-        $v const $name: $type = $type::from_u32_const($constant);
+        $v const $name: $type = $type::from_u32($constant);
         $crate::newtype_index!(
             @derives      [$($derives,)*]
             @attrs        [$(#[$attrs])*]

src/librustc_mir/lib.rs

@@ -9,6 +9,9 @@ Rust MIR: a lowered representation of Rust.
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
+#![feature(const_if_match)]
+#![feature(const_fn)]
+#![feature(const_panic)]
 #![feature(crate_visibility_modifier)]
 #![feature(drain_filter)]
 #![feature(exhaustive_patterns)]