Add reference annotations for diagnostic attributes

This adds reference annotations for `diagnostic::on_unimplmented` and
the `diagnostic` namespace in general.

tests/ui/diagnostic_namespace/deny_malformed_attribute.rs

@@ -1,3 +1,5 @@
+//@ reference: attributes.diagnostic.namespace.unknown-invalid-syntax
+
 #![deny(unknown_or_malformed_diagnostic_attributes)]
 
 #[diagnostic::unknown_attribute]

tests/ui/diagnostic_namespace/deny_malformed_attribute.stderr

@@ -1,11 +1,11 @@
 error: unknown diagnostic attribute
-  --> $DIR/deny_malformed_attribute.rs:3:15
+  --> $DIR/deny_malformed_attribute.rs:5:15
    |
 LL | #[diagnostic::unknown_attribute]
    |               ^^^^^^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/deny_malformed_attribute.rs:1:9
+  --> $DIR/deny_malformed_attribute.rs:3:9
    |
 LL | #![deny(unknown_or_malformed_diagnostic_attributes)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/ui/diagnostic_namespace/malformed_foreign_on_unimplemented.rs

@@ -1,5 +1,6 @@
 //@ edition:2021
 //@ aux-build:bad_on_unimplemented.rs
+//@ reference: attributes.diagnostic.on_unimplemented.syntax
 
 // Do not ICE when encountering a malformed `#[diagnostic::on_unimplemented]` annotation in a
 // dependency when incorrectly used (#124651).

tests/ui/diagnostic_namespace/malformed_foreign_on_unimplemented.stderr

@@ -1,19 +1,19 @@
 error[E0277]: the trait bound `(): bad_on_unimplemented::MissingAttr` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:22:18
+  --> $DIR/malformed_foreign_on_unimplemented.rs:23:18
    |
 LL |     missing_attr(());
    |     ------------ ^^ the trait `bad_on_unimplemented::MissingAttr` is not implemented for `()`
    |     |
    |     required by a bound introduced by this call
    |
 note: required by a bound in `missing_attr`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:11:20
+  --> $DIR/malformed_foreign_on_unimplemented.rs:12:20
    |
 LL | fn missing_attr<T: MissingAttr>(_: T) {}
    |                    ^^^^^^^^^^^ required by this bound in `missing_attr`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::DuplicateAttr` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:23:20
+  --> $DIR/malformed_foreign_on_unimplemented.rs:24:20
    |
 LL |     duplicate_attr(());
    |     -------------- ^^ a
@@ -22,55 +22,55 @@ LL |     duplicate_attr(());
    |
    = help: the trait `bad_on_unimplemented::DuplicateAttr` is not implemented for `()`
 note: required by a bound in `duplicate_attr`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:12:22
+  --> $DIR/malformed_foreign_on_unimplemented.rs:13:22
    |
 LL | fn duplicate_attr<T: DuplicateAttr>(_: T) {}
    |                      ^^^^^^^^^^^^^ required by this bound in `duplicate_attr`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::NotMetaList` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:24:19
+  --> $DIR/malformed_foreign_on_unimplemented.rs:25:19
    |
 LL |     not_meta_list(());
    |     ------------- ^^ the trait `bad_on_unimplemented::NotMetaList` is not implemented for `()`
    |     |
    |     required by a bound introduced by this call
    |
 note: required by a bound in `not_meta_list`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:13:21
+  --> $DIR/malformed_foreign_on_unimplemented.rs:14:21
    |
 LL | fn not_meta_list<T: NotMetaList>(_: T) {}
    |                     ^^^^^^^^^^^ required by this bound in `not_meta_list`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::Empty` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:25:11
+  --> $DIR/malformed_foreign_on_unimplemented.rs:26:11
    |
 LL |     empty(());
    |     ----- ^^ the trait `bad_on_unimplemented::Empty` is not implemented for `()`
    |     |
    |     required by a bound introduced by this call
    |
 note: required by a bound in `empty`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:14:13
+  --> $DIR/malformed_foreign_on_unimplemented.rs:15:13
    |
 LL | fn empty<T: Empty>(_: T) {}
    |             ^^^^^ required by this bound in `empty`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::WrongDelim` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:26:17
+  --> $DIR/malformed_foreign_on_unimplemented.rs:27:17
    |
 LL |     wrong_delim(());
    |     ----------- ^^ the trait `bad_on_unimplemented::WrongDelim` is not implemented for `()`
    |     |
    |     required by a bound introduced by this call
    |
 note: required by a bound in `wrong_delim`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:15:19
+  --> $DIR/malformed_foreign_on_unimplemented.rs:16:19
    |
 LL | fn wrong_delim<T: WrongDelim>(_: T) {}
    |                   ^^^^^^^^^^ required by this bound in `wrong_delim`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::BadFormatter<()>` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:27:19
+  --> $DIR/malformed_foreign_on_unimplemented.rs:28:19
    |
 LL |     bad_formatter(());
    |     ------------- ^^ ()
@@ -79,13 +79,13 @@ LL |     bad_formatter(());
    |
    = help: the trait `bad_on_unimplemented::BadFormatter<()>` is not implemented for `()`
 note: required by a bound in `bad_formatter`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:16:21
+  --> $DIR/malformed_foreign_on_unimplemented.rs:17:21
    |
 LL | fn bad_formatter<T: BadFormatter<()>>(_: T) {}
    |                     ^^^^^^^^^^^^^^^^ required by this bound in `bad_formatter`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::NoImplicitArgs` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:28:22
+  --> $DIR/malformed_foreign_on_unimplemented.rs:29:22
    |
 LL |     no_implicit_args(());
    |     ---------------- ^^ test {}
@@ -94,13 +94,13 @@ LL |     no_implicit_args(());
    |
    = help: the trait `bad_on_unimplemented::NoImplicitArgs` is not implemented for `()`
 note: required by a bound in `no_implicit_args`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:17:24
+  --> $DIR/malformed_foreign_on_unimplemented.rs:18:24
    |
 LL | fn no_implicit_args<T: NoImplicitArgs>(_: T) {}
    |                        ^^^^^^^^^^^^^^ required by this bound in `no_implicit_args`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::MissingArg` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:29:17
+  --> $DIR/malformed_foreign_on_unimplemented.rs:30:17
    |
 LL |     missing_arg(());
    |     ----------- ^^ {missing}
@@ -109,13 +109,13 @@ LL |     missing_arg(());
    |
    = help: the trait `bad_on_unimplemented::MissingArg` is not implemented for `()`
 note: required by a bound in `missing_arg`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:18:19
+  --> $DIR/malformed_foreign_on_unimplemented.rs:19:19
    |
 LL | fn missing_arg<T: MissingArg>(_: T) {}
    |                   ^^^^^^^^^^ required by this bound in `missing_arg`
 
 error[E0277]: the trait bound `(): bad_on_unimplemented::BadArg` is not satisfied
-  --> $DIR/malformed_foreign_on_unimplemented.rs:30:13
+  --> $DIR/malformed_foreign_on_unimplemented.rs:31:13
    |
 LL |     bad_arg(());
    |     ------- ^^ {_}
@@ -124,7 +124,7 @@ LL |     bad_arg(());
    |
    = help: the trait `bad_on_unimplemented::BadArg` is not implemented for `()`
 note: required by a bound in `bad_arg`
-  --> $DIR/malformed_foreign_on_unimplemented.rs:19:15
+  --> $DIR/malformed_foreign_on_unimplemented.rs:20:15
    |
 LL | fn bad_arg<T: BadArg>(_: T) {}
    |               ^^^^^^ required by this bound in `bad_arg`

tests/ui/diagnostic_namespace/non_existing_attributes_accepted.rs

@@ -1,4 +1,5 @@
 //@ check-pass
+//@ reference: attributes.diagnostic.namespace.unknown-invalid-syntax
 #[diagnostic::non_existing_attribute]
 //~^WARN unknown diagnostic attribute
 pub trait Bar {

tests/ui/diagnostic_namespace/non_existing_attributes_accepted.stderr

@@ -1,13 +1,13 @@
 warning: unknown diagnostic attribute
-  --> $DIR/non_existing_attributes_accepted.rs:2:15
+  --> $DIR/non_existing_attributes_accepted.rs:3:15
    |
 LL | #[diagnostic::non_existing_attribute]
    |               ^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(unknown_or_malformed_diagnostic_attributes)]` on by default
 
 warning: unknown diagnostic attribute
-  --> $DIR/non_existing_attributes_accepted.rs:7:15
+  --> $DIR/non_existing_attributes_accepted.rs:8:15
    |
 LL | #[diagnostic::non_existing_attribute(with_option = "foo")]
    |               ^^^^^^^^^^^^^^^^^^^^^^

tests/ui/diagnostic_namespace/on_unimplemented/broken_format.rs

@@ -1,3 +1,4 @@
+//@ reference: attributes.diagnostic.on_unimplemented.invalid-string
 #[diagnostic::on_unimplemented(message = "{{Test } thing")]
 //~^WARN unmatched `}` found
 //~|WARN unmatched `}` found