diff options
| -rw-r--r-- | src/libcore/ops/try.rs | 2 | ||||
| -rw-r--r-- | src/test/ui/suggestions/try-operator-on-main.rs | 13 | ||||
| -rw-r--r-- | src/test/ui/suggestions/try-operator-on-main.stderr | 14 |
3 files changed, 29 insertions, 0 deletions
diff --git a/src/libcore/ops/try.rs b/src/libcore/ops/try.rs index 2f0639d1a60..9da9879d38a 100644 --- a/src/libcore/ops/try.rs +++ b/src/libcore/ops/try.rs @@ -15,6 +15,8 @@ /// extracting those success or failure values from an existing instance and /// creating a new instance from a success or failure value. #[unstable(feature = "try_trait", issue = "42327")] +#[rustc_on_unimplemented = "the `?` operator can only be used in a function that returns `Result` \ + (or another type that implements `std::ops::Try`)"] pub trait Try { /// The type of this value when viewed as successful. #[unstable(feature = "try_trait", issue = "42327")] diff --git a/src/test/ui/suggestions/try-operator-on-main.rs b/src/test/ui/suggestions/try-operator-on-main.rs new file mode 100644 index 00000000000..55154e3507e --- /dev/null +++ b/src/test/ui/suggestions/try-operator-on-main.rs @@ -0,0 +1,13 @@ +// Copyright 2017 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 main() { + std::fs::File::open("foo")?; +} diff --git a/src/test/ui/suggestions/try-operator-on-main.stderr b/src/test/ui/suggestions/try-operator-on-main.stderr new file mode 100644 index 00000000000..cf0481bdab7 --- /dev/null +++ b/src/test/ui/suggestions/try-operator-on-main.stderr @@ -0,0 +1,14 @@ +error[E0277]: the trait bound `(): std::ops::Try` is not satisfied + --> $DIR/try-operator-on-main.rs:12:5 + | +12 | std::fs::File::open("foo")?; + | --------------------------- + | | + | the `?` operator can only be used in a function that returns `Result` (or another type that implements `std::ops::Try`) + | in this macro invocation + | + = help: the trait `std::ops::Try` is not implemented for `()` + = note: required by `std::ops::Try::from_error` + +error: aborting due to previous error + |