From ac3290e8d949448193014c85096f8772db331d46 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Esteban=20K=C3=BCber?= Date: Sun, 17 Mar 2019 22:42:51 -0700 Subject: [PATCH 1/3] Add suggestion to use `&*var` when `&str: From` is expected --- .../src/language-features/on-unimplemented.md | 12 ++++++++++++ src/libcore/convert.rs | 6 ++++++ src/test/ui/suggestions/into-str.rs | 6 ++++++ src/test/ui/suggestions/into-str.stderr | 17 +++++++++++++++++ 4 files changed, 41 insertions(+) create mode 100644 src/test/ui/suggestions/into-str.rs create mode 100644 src/test/ui/suggestions/into-str.stderr diff --git a/src/doc/unstable-book/src/language-features/on-unimplemented.md b/src/doc/unstable-book/src/language-features/on-unimplemented.md index f787f629756f3..b156038fba06d 100644 --- a/src/doc/unstable-book/src/language-features/on-unimplemented.md +++ b/src/doc/unstable-book/src/language-features/on-unimplemented.md @@ -138,3 +138,15 @@ error[E0277]: `&str` is not an iterator = help: the trait `std::iter::Iterator` is not implemented for `&str` = note: required by `std::iter::IntoIterator::into_iter` ``` + +If you need to filter on multiple attributes, you can use `all` in the following way: + +```rust,compile_fail +#[rustc_on_unimplemented( + on( + all(_Self="&str", T="std::string::String"), + note="you can coerce a `{T}` into a `{Self}` by writing `&*variable`" + ) +)] +pub trait From: Sized { /* ... */ } +``` \ No newline at end of file diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs index 774d648558b48..cb574a53dbccb 100644 --- a/src/libcore/convert.rs +++ b/src/libcore/convert.rs @@ -352,6 +352,12 @@ pub trait Into: Sized { /// [`from`]: trait.From.html#tymethod.from /// [book]: ../../book/ch09-00-error-handling.html #[stable(feature = "rust1", since = "1.0.0")] +#[rustc_on_unimplemented( + on( + all(_Self="&str", T="std::string::String"), + note="you can coerce a `{T}` into a `{Self}` by writing `&*variable`" + ) +)] pub trait From: Sized { /// Performs the conversion. #[stable(feature = "rust1", since = "1.0.0")] diff --git a/src/test/ui/suggestions/into-str.rs b/src/test/ui/suggestions/into-str.rs new file mode 100644 index 0000000000000..9793ee801d185 --- /dev/null +++ b/src/test/ui/suggestions/into-str.rs @@ -0,0 +1,6 @@ +fn foo<'a, T>(_t: T) where T: Into<&'a str> {} + +fn main() { + foo(String::new()); + //~^ ERROR the trait bound `&str: std::convert::From` is not satisfied +} diff --git a/src/test/ui/suggestions/into-str.stderr b/src/test/ui/suggestions/into-str.stderr new file mode 100644 index 0000000000000..f341d36370213 --- /dev/null +++ b/src/test/ui/suggestions/into-str.stderr @@ -0,0 +1,17 @@ +error[E0277]: the trait bound `&str: std::convert::From` is not satisfied + --> $DIR/into-str.rs:4:5 + | +LL | foo(String::new()); + | ^^^ the trait `std::convert::From` is not implemented for `&str` + | + = note: you can coerce a `std::string::String` into a `&str` by writing `&*variable` + = note: required because of the requirements on the impl of `std::convert::Into<&str>` for `std::string::String` +note: required by `foo` + --> $DIR/into-str.rs:1:1 + | +LL | fn foo<'a, T>(_t: T) where T: Into<&'a str> {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. From 2f7b32091ecdc86520d75aa8fe6bcffb5849732d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Esteban=20K=C3=BCber?= Date: Mon, 18 Mar 2019 11:06:48 -0700 Subject: [PATCH 2/3] extend on-unimplemented docs --- .../unstable-book/src/language-features/on-unimplemented.md | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/doc/unstable-book/src/language-features/on-unimplemented.md b/src/doc/unstable-book/src/language-features/on-unimplemented.md index b156038fba06d..a770ab65c26f8 100644 --- a/src/doc/unstable-book/src/language-features/on-unimplemented.md +++ b/src/doc/unstable-book/src/language-features/on-unimplemented.md @@ -139,7 +139,8 @@ error[E0277]: `&str` is not an iterator = note: required by `std::iter::IntoIterator::into_iter` ``` -If you need to filter on multiple attributes, you can use `all` in the following way: +If you need to filter on multiple attributes, you can use `all`, `any` or +`not` in the following way: ```rust,compile_fail #[rustc_on_unimplemented( @@ -149,4 +150,4 @@ If you need to filter on multiple attributes, you can use `all` in the following ) )] pub trait From: Sized { /* ... */ } -``` \ No newline at end of file +``` From e929d19edc99e5eb7af319709247470cff99719b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Esteban=20K=C3=BCber?= Date: Fri, 22 Mar 2019 20:38:09 -0700 Subject: [PATCH 3/3] review comments --- src/libcore/convert.rs | 2 +- src/test/ui/suggestions/into-str.stderr | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs index cb574a53dbccb..d36de3bbe8691 100644 --- a/src/libcore/convert.rs +++ b/src/libcore/convert.rs @@ -355,7 +355,7 @@ pub trait Into: Sized { #[rustc_on_unimplemented( on( all(_Self="&str", T="std::string::String"), - note="you can coerce a `{T}` into a `{Self}` by writing `&*variable`" + note="to coerce a `{T}` into a `{Self}`, use `&*` as a prefix", ) )] pub trait From: Sized { diff --git a/src/test/ui/suggestions/into-str.stderr b/src/test/ui/suggestions/into-str.stderr index f341d36370213..3e28700ce9552 100644 --- a/src/test/ui/suggestions/into-str.stderr +++ b/src/test/ui/suggestions/into-str.stderr @@ -4,7 +4,7 @@ error[E0277]: the trait bound `&str: std::convert::From` is LL | foo(String::new()); | ^^^ the trait `std::convert::From` is not implemented for `&str` | - = note: you can coerce a `std::string::String` into a `&str` by writing `&*variable` + = note: to coerce a `std::string::String` into a `&str`, use `&*` as a prefix = note: required because of the requirements on the impl of `std::convert::Into<&str>` for `std::string::String` note: required by `foo` --> $DIR/into-str.rs:1:1