Rollup merge of rust-lang#138019 - obi1kenobi:pg/pretty-print-more-attrs, r=compiler-errors

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 rust-lang#137645.

r? `@jdonszelmann`

Author: workingjubilee

compiler/rustc_hir_pretty/src/lib.rs

@@ -117,6 +117,80 @@ impl<'a> State<'a> {
                 ));
                 self.hardbreak()
             }
+            hir::Attribute::Parsed(AttributeKind::Deprecation { deprecation, .. }) => {
+                self.word("#[deprecated");
+
+                // There are three possible forms here:
+                // 1. a form with explicit components like
+                //    `#[deprecated(since = "1.2.3", note = "some note", suggestion = "something")]`
+                //    where each component may be present or absent.
+                // 2. `#[deprecated = "message"]`
+                // 3. `#[deprecated]`
+                //
+                // Let's figure out which we need.
+                // If there's a `since` or `suggestion` value, we're definitely in form 1.
+                if matches!(
+                    deprecation.since,
+                    rustc_attr_parsing::DeprecatedSince::RustcVersion(..)
+                        | rustc_attr_parsing::DeprecatedSince::Future
+                        | rustc_attr_parsing::DeprecatedSince::NonStandard(..)
+                ) || deprecation.suggestion.is_some()
+                {
+                    self.word("(");
+                    let mut use_comma = false;
+
+                    match &deprecation.since {
+                        rustc_attr_parsing::DeprecatedSince::RustcVersion(rustc_version) => {
+                            self.word("since = \"");
+                            self.word(format!(
+                                "{}.{}.{}",
+                                rustc_version.major, rustc_version.minor, rustc_version.patch
+                            ));
+                            self.word("\"");
+                            use_comma = true;
+                        }
+                        rustc_attr_parsing::DeprecatedSince::Future => {
+                            self.word("since = \"future\"");
+                            use_comma = true;
+                        }
+                        rustc_attr_parsing::DeprecatedSince::NonStandard(symbol) => {
+                            self.word("since = \"");
+                            self.word(symbol.to_ident_string());
+                            self.word("\"");
+                            use_comma = true;
+                        }
+                        _ => {}
+                    }
+
+                    if let Some(note) = &deprecation.note {
+                        if use_comma {
+                            self.word(", ");
+                        }
+                        self.word("note = \"");
+                        self.word(note.to_ident_string());
+                        self.word("\"");
+                        use_comma = true;
+                    }
+
+                    if let Some(suggestion) = &deprecation.suggestion {
+                        if use_comma {
+                            self.word(", ");
+                        }
+                        self.word("suggestion = \"");
+                        self.word(suggestion.to_ident_string());
+                        self.word("\"");
+                    }
+                } else if let Some(note) = &deprecation.note {
+                    // We're in form 2: `#[deprecated = "message"]`.
+                    self.word(" = \"");
+                    self.word(note.to_ident_string());
+                    self.word("\"");
+                } else {
+                    // We're in form 3: `#[deprecated]`. Nothing to do here.
+                }
+
+                self.word("]");
+            }
             hir::Attribute::Parsed(pa) => {
                 self.word("#[attr=\"");
                 pa.print_attribute(self);

tests/ui/unpretty/deprecated-attr.rs

@@ -0,0 +1,17 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#[deprecated]
+pub struct PlainDeprecated;
+
+#[deprecated = "here's why this is deprecated"]
+pub struct DirectNote;
+
+#[deprecated(note = "here's why this is deprecated")]
+pub struct ExplicitNote;
+
+#[deprecated(since = "1.2.3", note = "here's why this is deprecated")]
+pub struct SinceAndNote;
+
+#[deprecated(note = "here's why this is deprecated", since = "1.2.3")]
+pub struct FlippedOrder;

tests/ui/unpretty/deprecated-attr.stdout

@@ -0,0 +1,21 @@
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#[deprecated]
+struct PlainDeprecated;
+
+#[deprecated = "here's why this is deprecated"]
+struct DirectNote;
+
+#[deprecated = "here's why this is deprecated"]
+struct ExplicitNote;
+
+#[deprecated(since = "1.2.3", note = "here's why this is deprecated"]
+struct SinceAndNote;
+
+#[deprecated(since = "1.2.3", note = "here's why this is deprecated"]
+struct FlippedOrder;

tests/ui/unpretty/diagnostic-attr.rs

@@ -0,0 +1,13 @@
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#[diagnostic::on_unimplemented(
+    message = "My Message for `ImportantTrait<{A}>` implemented for `{Self}`",
+    label = "My Label",
+    note = "Note 1",
+    note = "Note 2"
+)]
+pub trait ImportantTrait<A> {}
+
+#[diagnostic::do_not_recommend]
+impl<T> ImportantTrait<T> for T where T: Clone {}

tests/ui/unpretty/diagnostic-attr.stdout

@@ -0,0 +1,16 @@
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ compile-flags: -Zunpretty=hir
+//@ check-pass
+
+#[diagnostic::on_unimplemented(message =
+"My Message for `ImportantTrait<{A}>` implemented for `{Self}`", label =
+"My Label", note = "Note 1", note = "Note 2")]
+trait ImportantTrait<A> { }
+
+#[diagnostic::do_not_recommend]
+impl <T> ImportantTrait<T> for T where T: Clone
+    {#![diagnostic::do_not_recommend]
+}