Auto merge of #29862 - ranma42:const_min_max, r=alexcrichton

They can be useful for constructing constant items.

Author: bors

src/libcore/num/mod.rs

@@ -124,15 +124,15 @@ macro_rules! int_impl {
         /// Returns the smallest value that can be represented by this integer type.
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
-        pub fn min_value() -> Self {
+        pub const fn min_value() -> Self {
             (-1 as Self) << ($BITS - 1)
         }
 
         /// Returns the largest value that can be represented by this integer type.
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
-        pub fn max_value() -> Self {
-            let min = Self::min_value(); !min
+        pub const fn max_value() -> Self {
+            !Self::min_value()
         }
 
         /// Converts a string slice in a given base to an integer.
@@ -891,12 +891,12 @@ macro_rules! uint_impl {
         /// Returns the smallest value that can be represented by this integer type.
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
-        pub fn min_value() -> Self { 0 }
+        pub const fn min_value() -> Self { 0 }
 
         /// Returns the largest value that can be represented by this integer type.
         #[stable(feature = "rust1", since = "1.0.0")]
         #[inline]
-        pub fn max_value() -> Self { !0 }
+        pub const fn max_value() -> Self { !0 }
 
         /// Converts a string slice in a given base to an integer.
         ///