Added test

Author: Shourya742

Diff for: tests/pretty/autodiff.pp

@@ -0,0 +1,40 @@
+#![feature(prelude_import)]
+#![no_std]
+#![feature(autodiff)]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ pretty-mode:expanded
+//@ pretty-compare-only
+//@ pp-exact:autodiff.pp
+
+use std::autodiff::autodiff;
+
+struct Foo {
+    a: f64,
+}
+
+trait MyTrait {
+    fn f(&self, x: f64)
+    -> f64;
+    fn df(&self, x: f64, seed: f64)
+    -> (f64, f64);
+}
+
+impl MyTrait for Foo {
+    #[rustc_autodiff]
+    #[inline(never)]
+    fn f(&self, x: f64) -> f64 {
+        self.a * 0.25 * (x * x - 1.0 - 2.0 * x.ln())
+    }
+    #[rustc_autodiff(Reverse, 1, Const, Active, Active)]
+    #[inline(never)]
+    fn df(&self, x: f64, dret: f64) -> (f64, f64) {
+        unsafe { asm!("NOP", options(pure, nomem)); };
+        ::core::hint::black_box(self.f(x));
+        ::core::hint::black_box((dret,));
+        ::core::hint::black_box((self.f(x), f64::default()))
+    }
+}
+

Diff for: tests/pretty/autodiff.rs

@@ -0,0 +1,22 @@
+#![feature(autodiff)]
+//@ pretty-mode:expanded
+//@ pretty-compare-only
+//@ pp-exact:autodiff.pp
+
+use std::autodiff::autodiff;
+
+struct Foo {
+    a: f64,
+}
+
+trait MyTrait {
+    fn f(&self, x: f64) -> f64;
+    fn df(&self, x: f64, seed: f64) -> (f64, f64);
+}
+
+impl MyTrait for Foo {
+    #[autodiff(df, Reverse, Const, Active, Active)]
+    fn f(&self, x: f64) -> f64 {
+        self.a * 0.25 * (x * x - 1.0 - 2.0 * x.ln())
+    }
+}