Rollup merge of #133108 - RalfJung:future-compat-needs-to-run, r=lcnr

lints_that_dont_need_to_run: never skip future-compat-reported lints

Follow-up to https://github.com/rust-lang/rust/pull/125116: future-compat lints show up with `--json=future-incompat` even if they are otherwise allowed in the crate. So let's ensure we do not skip those as part of the `lints_that_dont_need_to_run` logic.

I could not find a current future compat lint that is emitted by a lint pass, so there's no clear way to add a test for this.

Cc `@blyxyas` `@cjgillot`

3 files changed, 27 insertions, 16 deletions

diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index 97a95787422..4b1dafbdbee 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -123,17 +123,19 @@ fn lints_that_dont_need_to_run(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LintId> {
     let dont_need_to_run: FxIndexSet<LintId> = store
         .get_lints()
         .into_iter()
+        .filter(|lint| {
+            // Lints that show up in future-compat reports must always be run.
+            let has_future_breakage =
+                lint.future_incompatible.is_some_and(|fut| fut.reason.has_future_breakage());
+            !has_future_breakage && !lint.eval_always
+        })
         .filter_map(|lint| {
-            if !lint.eval_always {
-                let lint_level = map.lint_level_id_at_node(tcx, LintId::of(lint), CRATE_HIR_ID);
-                if matches!(lint_level, (Level::Allow, ..))
-                    || (matches!(lint_level, (.., LintLevelSource::Default)))
-                        && lint.default_level(tcx.sess.edition()) == Level::Allow
-                {
-                    Some(LintId::of(lint))
-                } else {
-                    None
-                }
+            let lint_level = map.lint_level_id_at_node(tcx, LintId::of(lint), CRATE_HIR_ID);
+            if matches!(lint_level, (Level::Allow, ..))
+                || (matches!(lint_level, (.., LintLevelSource::Default)))
+                    && lint.default_level(tcx.sess.edition()) == Level::Allow
+            {
+                Some(LintId::of(lint))
             } else {
                 None
             }
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index eac4afee050..c74fceeedba 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -466,6 +466,20 @@ impl FutureIncompatibilityReason {
             | FutureIncompatibilityReason::Custom(_) => None,
         }
     }
+
+    pub fn has_future_breakage(self) -> bool {
+        match self {
+            FutureIncompatibilityReason::FutureReleaseErrorReportInDeps => true,
+
+            FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
+            | FutureIncompatibilityReason::FutureReleaseSemanticsChange
+            | FutureIncompatibilityReason::EditionError(_)
+            | FutureIncompatibilityReason::EditionSemanticsChange(_)
+            | FutureIncompatibilityReason::EditionAndFutureReleaseError(_)
+            | FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(_)
+            | FutureIncompatibilityReason::Custom(_) => false,
+        }
+    }
 }
 
 impl FutureIncompatibleInfo {
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 92ba6ceee93..971d036fa69 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -290,12 +290,7 @@ pub fn lint_level(
         let has_future_breakage = future_incompatible.map_or(
             // Default allow lints trigger too often for testing.
             sess.opts.unstable_opts.future_incompat_test && lint.default_level != Level::Allow,
-            |incompat| {
-                matches!(
-                    incompat.reason,
-                    FutureIncompatibilityReason::FutureReleaseErrorReportInDeps
-                )
-            },
+            |incompat| incompat.reason.has_future_breakage(),
         );
 
         // Convert lint level to error level.