Auto merge of #140717 - mejrs:diagnostic_lints, r=oli-obk

Split up the `unknown_or_malformed_diagnostic_attributes` lint

This splits up the lint into the following lint group:
- `unknown_diagnostic_attributes` - triggers if the attribute is unknown to the current compiler
- `misplaced_diagnostic_attributes` - triggers if the attribute exists but it is not placed on the item kind it's meant for
- `malformed_diagnostic_attributes` - triggers if the attribute's syntax or options are invalid
- `malformed_diagnostic_format_literals` - triggers if the format string literal is invalid, for example if it has unpaired curly braces or invalid parameters
- this pr doesn't create it, but future lints for things like deprecations can also go here.

This PR does not start emitting lints in places that previously did not.

## Motivation

I want to have finer control over what `unknown_or_malformed_diagnostic_attributes` does

I have a project with fairly low msrv that is/will have a lower msrv than future diagnostic attributes. So lints will be emitted when I or others compile it on a lower msrv.

At this time, there are two options to silence these lints:

-  `#[allow(unknown_or_malformed_diagnostic_attributes)]` - this risks diagnostic regressions if I (or others) mess up using the attribute, or if the attribute's syntax ever changes.
- write a build script to detect the compiler version and emit cfgs, and then conditionally enable the attribute:
    ```rust
    #[cfg_attr(rust_version_99, diagnostic::new_attr_in_rust_99(thing = ..))]`
    struct Foo;
    ```
    or conditionally `allow`  the lint:
    ```rust
   // lib.rs
   #![cfg_attr(not(current_rust), allow(unknown_or_malformed_diagnostic_attributes))]
   ```

I like to avoid using build scripts if I can, so the following works much better for me. That is what this PR will let me do in the future:
```rust
    #[allow(unknown_diagnostic_attribute, reason = "attribute came out in rust 1.99 but msrv is 1.70")]
    #[diagnostic::new_attr_in_rust_99(thing = ..)]`
    struct Foo;

1 files changed, 89 insertions, 12 deletions

diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 15f0bad226d..a08d68e2d15 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -63,7 +63,10 @@ declare_lint_pass! {
         LOSSY_PROVENANCE_CASTS,
         MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
         MACRO_USE_EXTERN_CRATE,
+        MALFORMED_DIAGNOSTIC_ATTRIBUTES,
+        MALFORMED_DIAGNOSTIC_FORMAT_LITERALS,
         META_VARIABLE_MISUSE,
+        MISPLACED_DIAGNOSTIC_ATTRIBUTES,
         MISSING_ABI,
         MISSING_UNSAFE_ON_EXTERN,
         MUST_NOT_SUSPEND,
@@ -112,8 +115,8 @@ declare_lint_pass! {
         UNFULFILLED_LINT_EXPECTATIONS,
         UNINHABITED_STATIC,
         UNKNOWN_CRATE_TYPES,
+        UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
         UNKNOWN_LINTS,
-        UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
         UNNAMEABLE_TEST_ITEMS,
         UNNAMEABLE_TYPES,
         UNREACHABLE_CODE,
@@ -4284,32 +4287,106 @@ declare_lint! {
 }
 
 declare_lint! {
-    /// The `unknown_or_malformed_diagnostic_attributes` lint detects unrecognized or otherwise malformed
-    /// diagnostic attributes.
+    /// The `malformed_diagnostic_attributes` lint detects malformed diagnostic attributes.
     ///
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(diagnostic_namespace)]
-    /// #[diagnostic::does_not_exist]
-    /// struct Foo;
+    /// #[diagnostic::do_not_recommend(message = "message")]
+    /// trait Trait {}
     /// ```
     ///
     /// {{produces}}
     ///
+    /// ### Explanation
+    ///
+    /// It is usually a mistake to use options or syntax that is not supported. Check the spelling,
+    /// and check the diagnostic attribute listing for the correct name and syntax. Also consider if
+    /// you are using an old version of the compiler; perhaps the option or syntax is only available
+    /// in a newer version. See the [reference] for a list of diagnostic attributes and the syntax
+    /// of each.
+    ///
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/attributes/diagnostics.html#the-diagnostic-tool-attribute-namespace
+    pub MALFORMED_DIAGNOSTIC_ATTRIBUTES,
+    Warn,
+    "detects malformed diagnostic attributes",
+}
+
+declare_lint! {
+    /// The `misplaced_diagnostic_attributes` lint detects wrongly placed diagnostic attributes.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #[diagnostic::do_not_recommend]
+    /// struct NotUserFacing;
+    /// ```
+    ///
+    /// {{produces}}
     ///
     /// ### Explanation
     ///
-    /// It is usually a mistake to specify a diagnostic attribute that does not exist. Check
-    /// the spelling, and check the diagnostic attribute listing for the correct name. Also
-    /// consider if you are using an old version of the compiler, and the attribute
-    /// is only available in a newer version.
-    pub UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES,
+    /// It is usually a mistake to specify a diagnostic attribute on an item it is not meant for.
+    /// For example, `#[diagnostic::do_not_recommend]` can only be placed on trait implementations,
+    /// and does nothing if placed elsewhere. See the [reference] for a list of diagnostic
+    /// attributes and their correct positions.
+    ///
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/attributes/diagnostics.html#the-diagnostic-tool-attribute-namespace
+    pub MISPLACED_DIAGNOSTIC_ATTRIBUTES,
     Warn,
-    "unrecognized or malformed diagnostic attribute",
+    "detects diagnostic attributes that are placed on the wrong item",
 }
 
 declare_lint! {
+    /// The `unknown_diagnostic_attributes` lint detects unknown diagnostic attributes.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #[diagnostic::does_not_exist]
+    /// struct Thing;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// It is usually a mistake to specify a diagnostic attribute that does not exist. Check the
+    /// spelling, and check the diagnostic attribute listing for the correct name. Also consider if
+    /// you are using an old version of the compiler and the attribute is only available in a newer
+    /// version. See the [reference] for the list of diagnostic attributes.
+    ///
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/attributes/diagnostics.html#the-diagnostic-tool-attribute-namespace
+    pub UNKNOWN_DIAGNOSTIC_ATTRIBUTES,
+    Warn,
+    "detects unknown diagnostic attributes",
+}
+
+declare_lint! {
+    /// The `malformed_diagnostic_format_literals` lint detects malformed diagnostic format
+    /// literals.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #[diagnostic::on_unimplemented(message = "{Self}} does not implement `Trait`")]
+    /// trait Trait {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The `#[diagnostic::on_unimplemented]` attribute accepts string literal values that are
+    /// similar to `format!`'s string literal. See the [reference] for details on what is permitted
+    /// in this string literal.
+    ///
+    /// [reference]: https://doc.rust-lang.org/nightly/reference/attributes/diagnostics.html#the-diagnostic-tool-attribute-namespace
+    pub MALFORMED_DIAGNOSTIC_FORMAT_LITERALS,
+    Warn,
+    "detects diagnostic attribute with malformed diagnostic format literals",
+}
+declare_lint! {
     /// The `ambiguous_glob_imports` lint detects glob imports that should report ambiguity
     /// errors, but previously didn't do that due to rustc bugs.
     ///