From 93f8051626d94872186b8af3f8458f530de200c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Max=20K=C3=A4nner?= <max.kaenner@gmail.com>
Date: Thu, 6 Apr 2023 22:33:27 +0200
Subject: [PATCH] const Deref and const Neg impl

---
 Cargo.toml |  1 +
 src/lib.rs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index 20d7fd3..271eb7f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,3 +22,4 @@ default = ["std"]
 defmt = ["dep:defmt"]
 fixed = ["dep:fixed"]
 std = ["num-traits/std"]
+nightly = []
diff --git a/src/lib.rs b/src/lib.rs
index 5376956..59b9028 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,11 @@
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(feature = "nightly", feature(const_trait_impl))]
+#![cfg_attr(feature = "nightly", feature(trait_alias))]
 mod display;
 pub mod types;
 
+#[cfg(feature = "nightly")]
+use core::marker::Destruct;
 use core::{
     marker::PhantomData,
     ops::{
@@ -37,6 +41,7 @@ where
     _cd: PhantomData<Candela>,
 }
 
+#[cfg(not(feature = "nightly"))]
 impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> Deref
     for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>
 where
@@ -54,6 +59,24 @@ where
         &self.value
     }
 }
+#[cfg(feature = "nightly")]
+impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> const Deref
+    for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>
+where
+    Second: Integer,
+    Metre: Integer,
+    Kilogram: Integer,
+    Ampere: Integer,
+    Kelvin: Integer,
+    Mole: Integer,
+    Candela: Integer,
+{
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.value
+    }
+}
 
 impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> DerefMut
     for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>
@@ -71,6 +94,7 @@ where
     }
 }
 
+#[cfg(not(feature = "nightly"))]
 impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> Neg
     for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>
 where
@@ -89,6 +113,26 @@ where
         Self::Output::new(-self.value)
     }
 }
+#[cfg(feature = "nightly")]
+impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> const Neg
+    for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>
+where
+    Second: Integer,
+    Metre: Integer,
+    Kilogram: Integer,
+    Ampere: Integer,
+    Kelvin: Integer,
+    Mole: Integer,
+    Candela: Integer,
+    T: ~const Neg,
+    Self: ~const Destruct,
+{
+    type Output = SiUnit<T::Output, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>;
+
+    fn neg(self) -> Self::Output {
+        Self::Output::new(-self.value)
+    }
+}
 
 impl<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela> Zero
     for SiUnit<T, Second, Metre, Kilogram, Ampere, Kelvin, Mole, Candela>