1 files changed, 59 insertions, 0 deletions
diff --git a/compiler/rustc_lint/src/expect.rs b/compiler/rustc_lint/src/expect.rs
new file mode 100644
index 000000000..699e81543
--- /dev/null
+++ b/compiler/rustc_lint/src/expect.rs
@@ -0,0 +1,59 @@
+use crate::builtin;
+use rustc_errors::fluent;
+use rustc_hir::HirId;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::{lint::LintExpectation, ty::TyCtxt};
+use rustc_session::lint::LintExpectationId;
+use rustc_span::symbol::sym;
+use rustc_span::Symbol;
+
+pub(crate) fn provide(providers: &mut Providers) {
+    *providers = Providers { check_expectations, ..*providers };
+}
+
+fn check_expectations(tcx: TyCtxt<'_>, tool_filter: Option<Symbol>) {
+    if !tcx.sess.features_untracked().enabled(sym::lint_reasons) {
+        return;
+    }
+
+    let fulfilled_expectations = tcx.sess.diagnostic().steal_fulfilled_expectation_ids();
+    let lint_expectations = &tcx.lint_levels(()).lint_expectations;
+
+    for (id, expectation) in lint_expectations {
+        // This check will always be true, since `lint_expectations` only
+        // holds stable ids
+        if let LintExpectationId::Stable { hir_id, .. } = id {
+            if !fulfilled_expectations.contains(&id)
+                && tool_filter.map_or(true, |filter| expectation.lint_tool == Some(filter))
+            {
+                emit_unfulfilled_expectation_lint(tcx, *hir_id, expectation);
+            }
+        } else {
+            unreachable!("at this stage all `LintExpectationId`s are stable");
+        }
+    }
+}
+
+fn emit_unfulfilled_expectation_lint(
+    tcx: TyCtxt<'_>,
+    hir_id: HirId,
+    expectation: &LintExpectation,
+) {
+    tcx.struct_span_lint_hir(
+        builtin::UNFULFILLED_LINT_EXPECTATIONS,
+        hir_id,
+        expectation.emission_span,
+        |diag| {
+            let mut diag = diag.build(fluent::lint::expectation);
+            if let Some(rationale) = expectation.reason {
+                diag.note(rationale.as_str());
+            }
+
+            if expectation.is_unfulfilled_lint_expectations {
+                diag.note(fluent::lint::note);
+            }
+
+            diag.emit();
+        },
+    );
+}