Add a test for #32062

Add a test on @nikomatsakis suggestion for the improvement for equality relations implemented in rust-lang/rust#32062

issue-32062-equality-relations-complexity/issue-32062.rs

@@ -0,0 +1,60 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// This tests rustc performance when a large amount variables are created which all have equality
+// relations between them. With #32062 merged there should no longer be an exponentationl time
+// complexity for this test.
+
+fn main() {
+    let _ = test(Some(0).into_iter());
+}
+
+trait Parser {
+    type Input: Iterator;
+    type Output;
+    fn parse(self, input: Self::Input) -> Result<(Self::Output, Self::Input), ()>;
+    fn chain<P>(self, p: P) -> Chain<Self, P> where Self: Sized {
+        Chain(self, p)
+    }
+}
+
+struct Token<T>(T::Item) where T: Iterator;
+
+impl<T> Parser for Token<T> where T: Iterator {
+    type Input = T;
+    type Output = T::Item;
+    fn parse(self, _input: Self::Input) -> Result<(Self::Output, Self::Input), ()> {
+        Err(())
+    }
+}
+
+struct Chain<L, R>(L, R);
+
+impl<L, R> Parser for Chain<L, R> where L: Parser, R: Parser<Input = L::Input> {
+    type Input = L::Input;
+    type Output = (L::Output, R::Output);
+    fn parse(self, _input: Self::Input) -> Result<(Self::Output, Self::Input), ()> {
+        Err(())
+    }
+}
+
+fn test<I>(i: I) -> Result<((), I), ()> where I: Iterator<Item = i32> {
+    Chain(Token(0), Token(1))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .chain(Chain(Token(0), Token(1)))
+        .parse(i)
+        .map(|(_, i)| ((), i))
+}

issue-32062-equality-relations-complexity/makefile

@@ -0,0 +1,6 @@
+all:
+	$(RUSTC) issue-32062.rs -Ztime-passes -Zinput-stats
+touch:
+	rm hello
+clean:
+	rm hello