Pretty-print `#[deprecated]` attribute in HIR.
Pretty-print `#[deprecated]` attribute in a form closer to how it might appear in Rust source code, rather than using a `Debug`-like representation.
Consider the following Rust code:
```rust
#[deprecated]
pub struct PlainDeprecated;
#[deprecated = "here's why this is deprecated"]
pub struct DirectNote;
#[deprecated(since = "1.2.3", note = "here's why this is deprecated")]
pub struct SinceAndNote;
```
Here's the previous output:
```
#[attr="Deprecation{deprecation: Deprecation{since: Unspecifiednote:
suggestion: }span: }")]
struct PlainDeprecated;
#[attr="Deprecation{deprecation: Deprecation{since: Unspecifiednote:
here's why this is deprecatedsuggestion: }span: }")]
struct DirectNote;
#[attr="Deprecation{deprecation: Deprecation{since: NonStandard(1.2.3)note:
here's why this is deprecatedsuggestion: }span: }")]
struct SinceAndNote;
```
Here's the new output:
```rust
#[deprecated]
struct PlainDeprecated;
#[deprecated = "here's why this is deprecated"]
struct DirectNote;
#[deprecated(since = "1.2.3", note = "here's why this is deprecated"]
struct SinceAndNote;
```
Also includes a test for `#[diagnostic::(..)]` attributes, though their behavior is not changed here. I already wrote the test, so I figured it probably won't hurt to have it.
Related to discussion in #137645.
r? `@jdonszelmann`
UI Tests
This folder contains rustc's
UI tests.
Test Directives (Headers)
Typically, a UI test will have some test directives / headers which are special comments that tell compiletest how to build and interpret a test.
As part of an ongoing effort to rewrite compiletest
(see https://github.com/rust-lang/compiler-team/issues/536), a major
change proposal to change legacy compiletest-style headers // <directive>
to ui_test-style headers
//@ <directive> was accepted (see
https://github.com/rust-lang/compiler-team/issues/512.
An example directive is ignore-test. In legacy compiletest style, the header
would be written as
// ignore-test
but in ui_test style, the header would be written as
//@ ignore-test
compiletest is changed to accept only //@ directives for UI tests
(currently), and will reject and report an error if it encounters any
comments // <content> that may be parsed as a legacy compiletest-style
test header. To fix this, you should migrate to the ui_test-style header
//@ <content>.