From fa332b02450fdf5813aa82c8433f9565aff59466 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 30 Apr 2021 12:06:52 -0400
Subject: [PATCH] Revert "Add assert_matches!(expr, pat)."

This reverts commit eb18746bc6c6c5c710ad674873438cbad5894f06.
---
 library/core/src/macros/mod.rs | 54 ---------------------------
 library/core/src/panicking.rs  | 67 +++++++++++-----------------------
 library/std/src/lib.rs         |  5 +--
 3 files changed, 24 insertions(+), 102 deletions(-)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 99894b5605e..9a0c0a2817f 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -110,60 +110,6 @@ macro_rules! assert_ne {
     });
 }
 
-/// Asserts that an expression matches any of the given patterns.
-///
-/// Like in a `match` expression, the pattern can be optionally followed by `if`
-/// and a guard expression that has access to names bound by the pattern.
-///
-/// On panic, this macro will print the value of the expression with its
-/// debug representation.
-///
-/// Like [`assert!`], this macro has a second form, where a custom
-/// panic message can be provided.
-///
-/// # Examples
-///
-/// ```
-/// #![feature(assert_matches)]
-///
-/// let a = 1u32.checked_add(2);
-/// let b = 1u32.checked_sub(2);
-/// assert_matches!(a, Some(_));
-/// assert_matches!(b, None);
-///
-/// let c = Ok("abc".to_string());
-/// assert_matches!(c, Ok(x) | Err(x) if x.len() < 100);
-/// ```
-#[macro_export]
-#[unstable(feature = "assert_matches", issue = "82775")]
-#[allow_internal_unstable(core_panic)]
-macro_rules! assert_matches {
-    ($left:expr, $( $pattern:pat )|+ $( if $guard: expr )? $(,)?) => ({
-        match $left {
-            $( $pattern )|+ $( if $guard )? => {}
-            ref left_val => {
-                $crate::panicking::assert_matches_failed(
-                    left_val,
-                    $crate::stringify!($($pattern)|+ $(if $guard)?),
-                    $crate::option::Option::None
-                );
-            }
-        }
-    });
-    ($left:expr, $( $pattern:pat )|+ $( if $guard: expr )?, $($arg:tt)+) => ({
-        match $left {
-            $( $pattern )|+ $( if $guard )? => {}
-            ref left_val => {
-                $crate::panicking::assert_matches_failed(
-                    left_val,
-                    $crate::stringify!($($pattern)|+ $(if $guard)?),
-                    $crate::option::Option::Some($crate::format_args!($($arg)+))
-                );
-            }
-        }
-    });
-}
-
 /// Asserts that a boolean expression is `true` at runtime.
 ///
 /// This will invoke the [`panic!`] macro if the provided expression cannot be
diff --git a/library/core/src/panicking.rs b/library/core/src/panicking.rs
index 3e3e96fcd7f..35d9b2c5d26 100644
--- a/library/core/src/panicking.rs
+++ b/library/core/src/panicking.rs
@@ -97,7 +97,6 @@ pub fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
 pub enum AssertKind {
     Eq,
     Ne,
-    Match,
 }
 
 /// Internal function for `assert_eq!` and `assert_ne!` macros
@@ -114,54 +113,32 @@ where
     T: fmt::Debug + ?Sized,
     U: fmt::Debug + ?Sized,
 {
-    assert_failed_inner(kind, &left, &right, args)
-}
+    #[track_caller]
+    fn inner(
+        kind: AssertKind,
+        left: &dyn fmt::Debug,
+        right: &dyn fmt::Debug,
+        args: Option<fmt::Arguments<'_>>,
+    ) -> ! {
+        let op = match kind {
+            AssertKind::Eq => "==",
+            AssertKind::Ne => "!=",
+        };
 
-/// Internal function for `assert_match!`
-#[cold]
-#[track_caller]
-#[doc(hidden)]
-pub fn assert_matches_failed<T: fmt::Debug + ?Sized>(
-    left: &T,
-    right: &str,
-    args: Option<fmt::Arguments<'_>>,
-) -> ! {
-    // Use the Display implementation to display the pattern.
-    struct Pattern<'a>(&'a str);
-    impl fmt::Debug for Pattern<'_> {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            fmt::Display::fmt(self.0, f)
-        }
-    }
-    assert_failed_inner(AssertKind::Match, &left, &Pattern(right), args);
-}
-
-/// Non-generic version of the above functions, to avoid code bloat.
-#[track_caller]
-fn assert_failed_inner(
-    kind: AssertKind,
-    left: &dyn fmt::Debug,
-    right: &dyn fmt::Debug,
-    args: Option<fmt::Arguments<'_>>,
-) -> ! {
-    let op = match kind {
-        AssertKind::Eq => "==",
-        AssertKind::Ne => "!=",
-        AssertKind::Match => "matches",
-    };
-
-    match args {
-        Some(args) => panic!(
-            r#"assertion failed: `(left {} right)`
+        match args {
+            Some(args) => panic!(
+                r#"assertion failed: `(left {} right)`
   left: `{:?}`,
  right: `{:?}`: {}"#,
-            op, left, right, args
-        ),
-        None => panic!(
-            r#"assertion failed: `(left {} right)`
+                op, left, right, args
+            ),
+            None => panic!(
+                r#"assertion failed: `(left {} right)`
   left: `{:?}`,
  right: `{:?}`"#,
-            op, left, right,
-        ),
+                op, left, right,
+            ),
+        }
     }
+    inner(kind, &left, &right, args)
 }
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 8149858e103..51c2872e9ca 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -228,7 +228,6 @@
 #![feature(arbitrary_self_types)]
 #![feature(array_error_internals)]
 #![feature(asm)]
-#![feature(assert_matches)]
 #![feature(associated_type_bounds)]
 #![feature(atomic_mut_ptr)]
 #![feature(box_syntax)]
@@ -559,8 +558,8 @@ pub use std_detect::detect;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated, deprecated_in_future)]
 pub use core::{
-    assert_eq, assert_matches, assert_ne, debug_assert, debug_assert_eq, debug_assert_matches,
-    debug_assert_ne, matches, r#try, todo, unimplemented, unreachable, write, writeln,
+    assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_matches, debug_assert_ne,
+    matches, r#try, todo, unimplemented, unreachable, write, writeln,
 };
 
 // Re-export built-in macros defined through libcore.