Make newtype_index methods const

Author: ecstatic-morse

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
             }
         }