Use bool in favor of Option<()> for diagnostics

compiler/rustc_lint/src/builtin.rs

@@ -1330,7 +1330,7 @@ impl UnreachablePub {
                 BuiltinUnreachablePub {
                     what,
                     suggestion: (vis_span, applicability),
-                    help: exportable.then_some(()),
+                    help: exportable,
                 },
             );
         }

compiler/rustc_lint/src/errors.rs

@@ -77,7 +77,7 @@ pub struct UnknownToolInScopedLint {
     pub tool_name: Symbol,
     pub lint_name: String,
     #[help]
-    pub is_nightly_build: Option<()>,
+    pub is_nightly_build: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_lint/src/expect.rs

@@ -24,7 +24,7 @@ fn check_expectations(tcx: TyCtxt<'_>, tool_filter: Option<Symbol>) {
                 && tool_filter.map_or(true, |filter| expectation.lint_tool == Some(filter))
             {
                 let rationale = expectation.reason.map(|rationale| ExpectationNote { rationale });
-                let note = expectation.is_unfulfilled_lint_expectations.then_some(());
+                let note = expectation.is_unfulfilled_lint_expectations;
                 tcx.emit_node_span_lint(
                     UNFULFILLED_LINT_EXPECTATIONS,
                     *hir_id,

compiler/rustc_lint/src/levels.rs

@@ -936,7 +936,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                             span: tool_ident.map(|ident| ident.span),
                             tool_name: tool_name.unwrap(),
                             lint_name: pprust::path_to_string(&meta_item.path),
-                            is_nightly_build: sess.is_nightly_build().then_some(()),
+                            is_nightly_build: sess.is_nightly_build(),
                         });
                         continue;
                     }

compiler/rustc_lint/src/lints.rs

@@ -257,7 +257,7 @@ pub struct BuiltinUnreachablePub<'a> {
     #[suggestion(code = "pub(crate)")]
     pub suggestion: (Span, Applicability),
     #[help]
-    pub help: Option<()>,
+    pub help: bool,
 }
 
 #[derive(LintDiagnostic)]
@@ -572,7 +572,7 @@ pub struct Expectation {
     #[subdiagnostic]
     pub rationale: Option<ExpectationNote>,
     #[note]
-    pub note: Option<()>,
+    pub note: bool,
 }
 
 #[derive(Subdiagnostic)]
@@ -756,7 +756,7 @@ pub enum InvalidReferenceCastingDiag<'tcx> {
         #[label]
         orig_cast: Option<Span>,
         #[note(lint_invalid_reference_casting_note_ty_has_interior_mutability)]
-        ty_has_interior_mutability: Option<()>,
+        ty_has_interior_mutability: bool,
     },
     #[diag(lint_invalid_reference_casting_assign_to_ref)]
     #[note(lint_invalid_reference_casting_note_book)]
@@ -764,7 +764,7 @@ pub enum InvalidReferenceCastingDiag<'tcx> {
         #[label]
         orig_cast: Option<Span>,
         #[note(lint_invalid_reference_casting_note_ty_has_interior_mutability)]
-        ty_has_interior_mutability: Option<()>,
+        ty_has_interior_mutability: bool,
     },
     #[diag(lint_invalid_reference_casting_bigger_layout)]
     #[note(lint_layout)]

compiler/rustc_lint/src/reference_casting.rs

@@ -54,8 +54,6 @@ impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
                 && let Some(ty_has_interior_mutability) =
                     is_cast_from_ref_to_mut_ptr(cx, init, &mut peel_casts)
             {
-                let ty_has_interior_mutability = ty_has_interior_mutability.then_some(());
-
                 cx.emit_span_lint(
                     INVALID_REFERENCE_CASTING,
                     expr.span,