From 3ad1e4dfedf2c1b3670c90a71ac0aaf0d9d0416a Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Sun, 29 Nov 2020 15:19:07 -0500
Subject: [PATCH] WIP: make Infallible an alias for !

---
 library/core/src/convert/mod.rs | 65 +--------------------------------
 library/core/src/num/error.rs   |  8 ----
 library/std/src/error.rs        |  8 ----
 3 files changed, 1 insertion(+), 80 deletions(-)

diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index 3f7110b34cc67..827221d28e436 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -34,9 +34,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-use crate::fmt;
-use crate::hash::{Hash, Hasher};
-
 mod num;
 
 #[unstable(feature = "convert_float_to_int", issue = "67057")]
@@ -675,64 +672,4 @@ impl AsRef<str> for str {
 ///
 /// [never]: ../../std/primitive.never.html
 #[stable(feature = "convert_infallible", since = "1.34.0")]
-#[derive(Copy)]
-pub enum Infallible {}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl Clone for Infallible {
-    fn clone(&self) -> Infallible {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl fmt::Debug for Infallible {
-    fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl fmt::Display for Infallible {
-    fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl PartialEq for Infallible {
-    fn eq(&self, _: &Infallible) -> bool {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl Eq for Infallible {}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl PartialOrd for Infallible {
-    fn partial_cmp(&self, _other: &Self) -> Option<crate::cmp::Ordering> {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl Ord for Infallible {
-    fn cmp(&self, _other: &Self) -> crate::cmp::Ordering {
-        match *self {}
-    }
-}
-
-#[stable(feature = "convert_infallible", since = "1.34.0")]
-impl From<!> for Infallible {
-    fn from(x: !) -> Self {
-        x
-    }
-}
-
-#[stable(feature = "convert_infallible_hash", since = "1.44.0")]
-impl Hash for Infallible {
-    fn hash<H: Hasher>(&self, _: &mut H) {
-        match *self {}
-    }
-}
+pub type Infallible = !;
diff --git a/library/core/src/num/error.rs b/library/core/src/num/error.rs
index a42fc6feb16be..ce768c950453e 100644
--- a/library/core/src/num/error.rs
+++ b/library/core/src/num/error.rs
@@ -1,6 +1,5 @@
 //! Error types for conversion to integral types.
 
-use crate::convert::Infallible;
 use crate::fmt;
 
 /// The error type returned when a checked integral type conversion fails.
@@ -28,13 +27,6 @@ impl fmt::Display for TryFromIntError {
     }
 }
 
-#[stable(feature = "try_from", since = "1.34.0")]
-impl From<Infallible> for TryFromIntError {
-    fn from(x: Infallible) -> TryFromIntError {
-        match x {}
-    }
-}
-
 #[stable(feature = "never_type", since = "1.49.0")]
 impl From<!> for TryFromIntError {
     fn from(never: !) -> TryFromIntError {
diff --git a/library/std/src/error.rs b/library/std/src/error.rs
index 6e6a1b76fd755..edeaa012ebeb7 100644
--- a/library/std/src/error.rs
+++ b/library/std/src/error.rs
@@ -17,7 +17,6 @@
 mod tests;
 
 use core::array;
-use core::convert::Infallible;
 
 use crate::alloc::{AllocError, LayoutError};
 use crate::any::TypeId;
@@ -456,13 +455,6 @@ impl Error for string::FromUtf16Error {
     }
 }
 
-#[stable(feature = "str_parse_error2", since = "1.8.0")]
-impl Error for Infallible {
-    fn description(&self) -> &str {
-        match *self {}
-    }
-}
-
 #[stable(feature = "decode_utf16", since = "1.9.0")]
 impl Error for char::DecodeUtf16Error {
     #[allow(deprecated)]