Auto merge of #13805 - Muscraft:im-a-teapot-lint-unstable, r=epage

Error when unstable lints are specified but not enabled

In [#13797, it was noted that](#13797 (comment)) the `im-a-teapot` lint should always be unstable. This PR makes it so that `im-a-teapot` is unstable, and it is an error to specify it without the `test-dummy-unstable` cargo feature.

It does this by adding a `feature-gate` field to `Lint` and `LintGroup` that optionally
puts the lint/lint group behind a feature. The `feature-gate` is then checked during the new `analyze_cargo_lints_table` step that runs across all lints (and groups) specified in `[lints.cargo]` or `[workspace.lints]` if the package is inheriting its lints from a workspace.

The error looks like the following:
No inherit
![No inherit](https://github.com/rust-lang/cargo/assets/23045215/c245af87-8623-42dc-9652-be461809bb30)
Inherited
![Inhrtited](https://github.com/rust-lang/cargo/assets/23045215/5a90b7c9-0e9e-4a07-ab0e-e2e43cca8991)

Author: bors

src/cargo/core/features.rs

@@ -343,7 +343,7 @@ impl FromStr for Edition {
     }
 }
 
-#[derive(PartialEq)]
+#[derive(Debug, PartialEq)]
 enum Status {
     Stable,
     Unstable,
@@ -387,11 +387,11 @@ macro_rules! features {
             $(
                 $(#[$attr])*
                 #[doc = concat!("\n\n\nSee <https://doc.rust-lang.org/nightly/cargo/", $docs, ">.")]
-                pub fn $feature() -> &'static Feature {
+                pub const fn $feature() -> &'static Feature {
                     fn get(features: &Features) -> bool {
                         stab!($stab) == Status::Stable || features.$feature
                     }
-                    static FEAT: Feature = Feature {
+                    const FEAT: Feature = Feature {
                         name: stringify!($feature),
                         stability: stab!($stab),
                         version: $version,
@@ -406,6 +406,10 @@ macro_rules! features {
             fn is_enabled(&self, features: &Features) -> bool {
                 (self.get)(features)
             }
+
+            pub(crate) fn name(&self) -> &str {
+                self.name
+            }
         }
 
         impl Features {
@@ -512,6 +516,7 @@ features! {
 }
 
 /// Status and metadata for a single unstable feature.
+#[derive(Debug)]
 pub struct Feature {
     /// Feature name. This is valid Rust identifier so no dash only underscore.
     name: &'static str,

src/cargo/core/workspace.rs

@@ -24,7 +24,9 @@ use crate::sources::{PathSource, CRATES_IO_INDEX, CRATES_IO_REGISTRY};
 use crate::util::edit_distance;
 use crate::util::errors::{CargoResult, ManifestError};
 use crate::util::interning::InternedString;
-use crate::util::lints::{check_im_a_teapot, check_implicit_features, unused_dependencies};
+use crate::util::lints::{
+    analyze_cargo_lints_table, check_im_a_teapot, check_implicit_features, unused_dependencies,
+};
 use crate::util::toml::{read_manifest, InheritableFields};
 use crate::util::{
     context::CargoResolverConfig, context::CargoResolverPrecedence, context::ConfigRelativePath,
@@ -1227,6 +1229,26 @@ impl<'gctx> Workspace<'gctx> {
             .is_some_and(|l| l.workspace)
             .then(|| ws_cargo_lints);
 
+        let ws_contents = match self.root_maybe() {
+            MaybePackage::Package(pkg) => pkg.manifest().contents(),
+            MaybePackage::Virtual(v) => v.contents(),
+        };
+
+        let ws_document = match self.root_maybe() {
+            MaybePackage::Package(pkg) => pkg.manifest().document(),
+            MaybePackage::Virtual(v) => v.document(),
+        };
+
+        analyze_cargo_lints_table(
+            pkg,
+            &path,
+            &normalized_lints,
+            ws_cargo_lints,
+            ws_contents,
+            ws_document,
+            self.root_manifest(),
+            self.gctx,
+        )?;
         check_im_a_teapot(
             pkg,
             &path,