test: add more extensive tests for impl Trait.

src/test/compile-fail/impl-trait/disallowed-2.rs

@@ -0,0 +1,18 @@
+// 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.
+
+#![feature(conservative_impl_trait)]
+
+fn main() {
+    let _: impl Fn() = || {};
+    //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+    let _ = || -> impl Fn() { || {} };
+    //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+}

src/test/compile-fail/impl-trait/disallowed.rs

@@ -0,0 +1,61 @@
+// 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.
+
+#![feature(conservative_impl_trait)]
+
+fn arguments(_: impl Fn(),
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+             _: Vec<impl Clone>) {}
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+
+type Factory<R> = impl Fn() -> R;
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+
+type GlobalFactory<R> = fn() -> impl FnOnce() -> R;
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+
+trait LazyToString {
+    fn lazy_to_string<'a>(&'a self) -> impl Fn() -> String;
+    //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+}
+
+// Note that the following impl doesn't error, because the trait is invalid.
+impl LazyToString for String {
+    fn lazy_to_string<'a>(&'a self) -> impl Fn() -> String {
+        || self.clone()
+    }
+}
+
+#[derive(Copy, Clone)]
+struct Lazy<T>(T);
+
+impl std::ops::Add<Lazy<i32>> for Lazy<i32> {
+    type Output = impl Fn() -> Lazy<i32>;
+    //~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+
+    fn add(self, other: Lazy<i32>) -> Self::Output {
+        move || Lazy(self.0 + other.0)
+    }
+}
+
+impl<F> std::ops::Add<F>
+for impl Fn() -> Lazy<i32>
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+where F: Fn() -> impl FnOnce() -> i32
+//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
+{
+    type Output = Self;
+
+    fn add(self, other: F) -> Self::Output {
+        move || Lazy(self().0 + other()())
+    }
+}
+
+fn main() {}

src/test/compile-fail/impl-trait/equality.rs

@@ -0,0 +1,89 @@
+// 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.
+
+#![feature(conservative_impl_trait, specialization)]
+
+trait Foo: Copy + ToString {}
+
+impl<T: Copy + ToString> Foo for T {}
+
+fn hide<T: Foo>(x: T) -> impl Foo {
+    x
+}
+
+fn two(x: bool) -> impl Foo {
+    if x {
+        return 1_i32;
+    }
+    0_u32
+    //~^ ERROR mismatched types
+    //~| expected i32, found u32
+}
+
+fn sum_to(n: u32) -> impl Foo {
+    if n == 0 {
+        0
+    } else {
+        n + sum_to(n - 1)
+        //~^ ERROR the trait bound `u32: std::ops::Add<impl Foo>` is not satisfied
+    }
+}
+
+trait Leak: Sized {
+    type T;
+    fn leak(self) -> Self::T;
+}
+impl<T> Leak for T {
+    default type T = ();
+    default fn leak(self) -> Self::T { panic!() }
+}
+impl Leak for i32 {
+    type T = i32;
+    fn leak(self) -> i32 { self }
+}
+
+trait CheckIfSend: Sized {
+    type T: Default;
+    fn check(self) -> Self::T { Default::default() }
+}
+impl<T> CheckIfSend for T {
+    default type T = ();
+}
+impl<T: Send> CheckIfSend for T {
+    type T = bool;
+}
+
+fn main() {
+    let _: u32 = hide(0_u32);
+    //~^ ERROR mismatched types
+    //~| expected type `u32`
+    //~| found type `impl Foo`
+    //~| expected u32, found anonymized type
+
+    let _: i32 = Leak::leak(hide(0_i32));
+    //~^ ERROR mismatched types
+    //~| expected type `i32`
+    //~| found type `<impl Foo as Leak>::T`
+    //~| expected i32, found associated type
+
+    let _: bool = CheckIfSend::check(hide(0_i32));
+    //~^ ERROR mismatched types
+    //~| expected type `bool`
+    //~| found type `<impl Foo as CheckIfSend>::T`
+    //~| expected bool, found associated type
+
+    let mut x = (hide(0_u32), hide(0_i32));
+    x = (x.1,
+    //~^ ERROR mismatched types
+    //~| expected u32, found i32
+         x.0);
+    //~^ ERROR mismatched types
+    //~| expected i32, found u32
+}

src/test/compile-fail/impl-trait/feature-gate.rs

@@ -0,0 +1,14 @@
+// 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.
+
+fn foo() -> impl Fn() { || {} }
+//~^ ERROR `impl Trait` is experimental
+
+fn main() {}

src/test/compile-fail/impl-trait/lifetimes.rs

@@ -0,0 +1,43 @@
+// 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.
+
+#![feature(conservative_impl_trait)]
+
+// Helper creating a fake borrow, captured by the impl Trait.
+fn borrow<'a, T>(_: &'a mut T) -> impl Copy { () }
+
+fn stack() -> impl Copy {
+    //~^ ERROR only named lifetimes are allowed in `impl Trait`
+    let x = 0;
+    &x
+}
+
+fn late_bound(x: &i32) -> impl Copy {
+    //~^ ERROR only named lifetimes are allowed in `impl Trait`
+    x
+}
+
+// FIXME(#34511) Should work but doesn't at the moment,
+// region-checking needs an overhault to support this.
+fn early_bound<'a>(x: &'a i32) -> impl Copy {
+    //~^ ERROR only named lifetimes are allowed in `impl Trait`
+    x
+}
+
+fn ambiguous<'a, 'b>(x: &'a [u32], y: &'b [u32]) -> impl Iterator<Item=u32> {
+    //~^ ERROR only named lifetimes are allowed in `impl Trait`
+    if x.len() < y.len() {
+        x.iter().cloned()
+    } else {
+        y.iter().cloned()
+    }
+}
+
+fn main() {}

src/test/compile-fail/impl-trait/loan-extend.rs

@@ -0,0 +1,23 @@
+// 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.
+
+#![feature(conservative_impl_trait)]
+
+// Helper creating a fake borrow, captured by the impl Trait.
+fn borrow<'a, T>(_: &'a mut T) -> impl Copy { () }
+
+fn main() {
+    //~^ NOTE reference must be valid for the block
+    let long;
+    let mut short = 0;
+    //~^ NOTE but borrowed value is only valid for the block suffix following statement 1
+    long = borrow(&mut short);
+    //~^ ERROR `short` does not live long enough
+}

src/test/run-pass/impl-trait/equality.rs

@@ -0,0 +1,43 @@
+// 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.
+
+#![feature(conservative_impl_trait, specialization)]
+
+trait Foo: std::fmt::Debug + Eq {}
+
+impl<T: std::fmt::Debug + Eq> Foo for T {}
+
+fn hide<T: Foo>(x: T) -> impl Foo {
+    x
+}
+
+trait Leak<T>: Sized {
+    fn leak(self) -> T;
+}
+impl<T, U> Leak<T> for U {
+    default fn leak(self) -> T { panic!("type mismatch") }
+}
+impl<T> Leak<T> for T {
+    fn leak(self) -> T { self }
+}
+
+fn lucky_seven() -> impl Fn(usize) -> u8 {
+    let a = [1, 2, 3, 4, 5, 6, 7];
+    move |i| a[i]
+}
+
+fn main() {
+    assert_eq!(hide(42), hide(42));
+
+    assert_eq!(std::mem::size_of_val(&hide([0_u8; 5])), 5);
+    assert_eq!(std::mem::size_of_val(&lucky_seven()), 7);
+
+    assert_eq!(Leak::<i32>::leak(hide(5_i32)), 5_i32);
+}