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Auto merge of #50441 - kornelski:debughint, r=kornelski

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Suggest more helpful formatting string

Based on [user feedback](https://users.rust-lang.org/t/ux-feedback-from-a-rust-newbie/17220) the minimal suggestion of `:?` is unclear.

Also `{:#?}` is much more readable than the standard debug, so this PR suggests it to help surface this nice feature.
This commit is contained in:
bors 2018-05-05 14:29:42 +00:00
commit fa30ae5c7e
2 changed files with 13 additions and 9 deletions
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11
src/libcore/fmt/mod.rs
View File

@ -542,10 +542,10 @@ impl<'a> Display for Arguments<'a> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_on_unimplemented(
on(crate_local, label="`{Self}` cannot be formatted using `:?`; \
add `#[derive(Debug)]` or manually implement `{Debug}`"),
on(crate_local, label="`{Self}` cannot be formatted using `{{:?}}`",
note="add `#[derive(Debug)]` or manually implement `{Debug}`"),
message="`{Self}` doesn't implement `{Debug}`",
label="`{Self}` cannot be formatted using `:?` because it doesn't implement `{Debug}`",
label="`{Self}` cannot be formatted using `{{:?}}` because it doesn't implement `{Debug}`",
)]
#[doc(alias = "{:?}")]
#[lang = "debug_trait"]
@ -610,8 +610,9 @@ pub trait Debug {
/// ```
#[rustc_on_unimplemented(
message="`{Self}` doesn't implement `{Display}`",
label="`{Self}` cannot be formatted with the default formatter; \
try using `:?` instead if you are using a format string",
label="`{Self}` cannot be formatted with the default formatter",
note="in format strings you may be able to use `{{:?}}` \
(or {{:#?}} for pretty-print) instead",
)]
#[doc(alias = "{}")]
#[stable(feature = "rust1", since = "1.0.0")]

11
src/test/ui/on-unimplemented/no-debug.stderr
View File

@ -2,16 +2,17 @@ error[E0277]: `Foo` doesn't implement `std::fmt::Debug`
--> $DIR/no-debug.rs:20:27
|
LL | println!("{:?} {:?}", Foo, Bar);
| ^^^ `Foo` cannot be formatted using `:?`; add `#[derive(Debug)]` or manually implement `std::fmt::Debug`
| ^^^ `Foo` cannot be formatted using `{:?}`
|
= help: the trait `std::fmt::Debug` is not implemented for `Foo`
= note: add `#[derive(Debug)]` or manually implement `std::fmt::Debug`
= note: required by `std::fmt::Debug::fmt`
error[E0277]: `no_debug::Bar` doesn't implement `std::fmt::Debug`
--> $DIR/no-debug.rs:20:32
|
LL | println!("{:?} {:?}", Foo, Bar);
| ^^^ `no_debug::Bar` cannot be formatted using `:?` because it doesn't implement `std::fmt::Debug`
| ^^^ `no_debug::Bar` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
|
= help: the trait `std::fmt::Debug` is not implemented for `no_debug::Bar`
= note: required by `std::fmt::Debug::fmt`
@ -20,18 +21,20 @@ error[E0277]: `Foo` doesn't implement `std::fmt::Display`
--> $DIR/no-debug.rs:21:23
|
LL | println!("{} {}", Foo, Bar);
| ^^^ `Foo` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
| ^^^ `Foo` cannot be formatted with the default formatter
|
= help: the trait `std::fmt::Display` is not implemented for `Foo`
= note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
= note: required by `std::fmt::Display::fmt`
error[E0277]: `no_debug::Bar` doesn't implement `std::fmt::Display`
--> $DIR/no-debug.rs:21:28
|
LL | println!("{} {}", Foo, Bar);
| ^^^ `no_debug::Bar` cannot be formatted with the default formatter; try using `:?` instead if you are using a format string
| ^^^ `no_debug::Bar` cannot be formatted with the default formatter
|
= help: the trait `std::fmt::Display` is not implemented for `no_debug::Bar`
= note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
= note: required by `std::fmt::Display::fmt`
error: aborting due to 4 previous errors