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

compiler/rustc_ast_lowering/src/asm.rs

@@ -86,9 +86,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 // Multiple different abi names may actually be the same ABI
                                 // If the specified ABIs are not the same name, alert the user that they resolve to the same ABI
                                 let source_map = self.tcx.sess.source_map();
-                                let equivalent = (source_map.span_to_snippet(*prev_sp)
-                                    != source_map.span_to_snippet(*abi_span))
-                                .then_some(());
+                                let equivalent = source_map.span_to_snippet(*prev_sp)
+                                    != source_map.span_to_snippet(*abi_span);
 
                                 self.dcx().emit_err(AbiSpecifiedMultipleTimes {
                                     abi_span: *abi_span,

compiler/rustc_ast_lowering/src/errors.rs

@@ -184,7 +184,7 @@ pub struct AbiSpecifiedMultipleTimes {
     #[label]
     pub prev_span: Span,
     #[note]
-    pub equivalent: Option<()>,
+    pub equivalent: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -963,14 +963,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 self_ty,
                 items,
             }) => {
-                let error =
-                    |annotation_span, annotation, only_trait: bool| errors::InherentImplCannot {
-                        span: self_ty.span,
-                        annotation_span,
-                        annotation,
-                        self_ty: self_ty.span,
-                        only_trait: only_trait.then_some(()),
-                    };
+                let error = |annotation_span, annotation, only_trait| errors::InherentImplCannot {
+                    span: self_ty.span,
+                    annotation_span,
+                    annotation,
+                    self_ty: self_ty.span,
+                    only_trait,
+                };
 
                 self.with_in_trait_impl(None, |this| {
                     this.visibility_not_permitted(
@@ -1195,7 +1194,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 } else if where_clauses.after.has_where_token {
                     self.dcx().emit_err(errors::WhereClauseAfterTypeAlias {
                         span: where_clauses.after.span,
-                        help: self.session.is_nightly_build().then_some(()),
+                        help: self.session.is_nightly_build(),
                     });
                 }
             }

compiler/rustc_ast_passes/src/errors.rs

@@ -484,7 +484,7 @@ pub struct InherentImplCannot<'a> {
     #[label(ast_passes_type)]
     pub self_ty: Span,
     #[note(ast_passes_only_trait)]
-    pub only_trait: Option<()>,
+    pub only_trait: bool,
 }
 
 #[derive(Diagnostic)]
@@ -528,7 +528,7 @@ pub struct WhereClauseAfterTypeAlias {
     #[primary_span]
     pub span: Span,
     #[help]
-    pub help: Option<()>,
+    pub help: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_attr/src/builtin.rs

@@ -846,7 +846,7 @@ pub fn find_deprecation(
                                     sess.dcx().emit_err(
                                         session_diagnostics::DeprecatedItemSuggestion {
                                             span: mi.span,
-                                            is_nightly: sess.is_nightly_build().then_some(()),
+                                            is_nightly: sess.is_nightly_build(),
                                             details: (),
                                         },
                                     );

compiler/rustc_attr/src/session_diagnostics.rs

@@ -342,7 +342,7 @@ pub(crate) struct DeprecatedItemSuggestion {
     pub span: Span,
 
     #[help]
-    pub is_nightly: Option<()>,
+    pub is_nightly: bool,
 
     #[note]
     pub details: (),

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -384,7 +384,7 @@ impl<'tcx> NonConstOp<'tcx> for HeapAllocation {
         ccx.dcx().create_err(errors::UnallowedHeapAllocations {
             span,
             kind: ccx.const_kind(),
-            teach: ccx.tcx.sess.teach(E0010).then_some(()),
+            teach: ccx.tcx.sess.teach(E0010),
         })
     }
 }
@@ -444,16 +444,16 @@ impl<'tcx> NonConstOp<'tcx> for CellBorrow {
         if let hir::ConstContext::Static(_) = ccx.const_kind() {
             ccx.dcx().create_err(errors::InteriorMutableDataRefer {
                 span,
-                opt_help: Some(()),
+                opt_help: true,
                 kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492).then_some(()),
+                teach: ccx.tcx.sess.teach(E0492),
             })
         } else {
             ccx.dcx().create_err(errors::InteriorMutableDataRefer {
                 span,
-                opt_help: None,
+                opt_help: false,
                 kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0492).then_some(()),
+                teach: ccx.tcx.sess.teach(E0492),
             })
         }
     }
@@ -481,12 +481,12 @@ impl<'tcx> NonConstOp<'tcx> for MutBorrow {
             hir::BorrowKind::Raw => ccx.tcx.dcx().create_err(errors::UnallowedMutableRaw {
                 span,
                 kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0764).then_some(()),
+                teach: ccx.tcx.sess.teach(E0764),
             }),
             hir::BorrowKind::Ref => ccx.dcx().create_err(errors::UnallowedMutableRefs {
                 span,
                 kind: ccx.const_kind(),
-                teach: ccx.tcx.sess.teach(E0764).then_some(()),
+                teach: ccx.tcx.sess.teach(E0764),
             }),
         }
     }

compiler/rustc_const_eval/src/errors.rs

@@ -151,7 +151,7 @@ pub(crate) struct UnallowedMutableRefs {
     pub span: Span,
     pub kind: ConstContext,
     #[note(const_eval_teach_note)]
-    pub teach: Option<()>,
+    pub teach: bool,
 }
 
 #[derive(Diagnostic)]
@@ -161,7 +161,7 @@ pub(crate) struct UnallowedMutableRaw {
     pub span: Span,
     pub kind: ConstContext,
     #[note(const_eval_teach_note)]
-    pub teach: Option<()>,
+    pub teach: bool,
 }
 #[derive(Diagnostic)]
 #[diag(const_eval_non_const_fmt_macro_call, code = E0015)]
@@ -196,7 +196,7 @@ pub(crate) struct UnallowedHeapAllocations {
     pub span: Span,
     pub kind: ConstContext,
     #[note(const_eval_teach_note)]
-    pub teach: Option<()>,
+    pub teach: bool,
 }
 
 #[derive(Diagnostic)]
@@ -214,10 +214,10 @@ pub(crate) struct InteriorMutableDataRefer {
     #[label]
     pub span: Span,
     #[help]
-    pub opt_help: Option<()>,
+    pub opt_help: bool,
     pub kind: ConstContext,
     #[note(const_eval_teach_note)]
-    pub teach: Option<()>,
+    pub teach: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_expand/src/errors.rs

@@ -281,7 +281,7 @@ pub(crate) struct IncompleteParse<'a> {
     pub macro_path: &'a ast::Path,
     pub kind_name: &'a str,
     #[note(expand_macro_expands_to_match_arm)]
-    pub expands_to_match_arm: Option<()>,
+    pub expands_to_match_arm: bool,
 
     #[suggestion(
         expand_suggestion_add_semi,

compiler/rustc_expand/src/expand.rs

@@ -1031,7 +1031,7 @@ pub(crate) fn ensure_complete_parse<'a>(
             label_span: span,
             macro_path,
             kind_name,
-            expands_to_match_arm: expands_to_match_arm.then_some(()),
+            expands_to_match_arm,
             add_semicolon,
         });
     }

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1564,7 +1564,7 @@ fn check_type_alias_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalD
             // * compare the param span to the pred span to detect lone user-written `Sized` bounds
             let has_explicit_bounds = bounded_params.is_empty()
                 || (*bounded_params).get(&param.index).is_some_and(|&&pred_sp| pred_sp != span);
-            let const_param_help = (!has_explicit_bounds).then_some(());
+            let const_param_help = !has_explicit_bounds;
 
             let mut diag = tcx.dcx().create_err(errors::UnusedGenericParameter {
                 span,

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1972,8 +1972,7 @@ fn report_bivariance<'tcx>(
     }
 
     let const_param_help =
-        matches!(param.kind, hir::GenericParamKind::Type { .. } if !has_explicit_bounds)
-            .then_some(());
+        matches!(param.kind, hir::GenericParamKind::Type { .. } if !has_explicit_bounds);
 
     let mut diag = tcx.dcx().create_err(errors::UnusedGenericParameter {
         span: param.span,

compiler/rustc_hir_analysis/src/errors.rs

@@ -1606,7 +1606,7 @@ pub(crate) struct UnusedGenericParameter {
     #[subdiagnostic]
     pub help: UnusedGenericParameterHelp,
     #[help(hir_analysis_const_param_help)]
-    pub const_param_help: Option<()>,
+    pub const_param_help: bool,
 }
 
 #[derive(Diagnostic)]
@@ -1643,9 +1643,9 @@ pub(crate) struct UnconstrainedGenericParameter {
     pub param_name: Symbol,
     pub param_def_kind: &'static str,
     #[note(hir_analysis_const_param_note)]
-    pub const_param_note: Option<()>,
+    pub const_param_note: bool,
     #[note(hir_analysis_const_param_note2)]
-    pub const_param_note2: Option<()>,
+    pub const_param_note2: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_analysis/src/impl_wf_check.rs

@@ -137,8 +137,7 @@ fn enforce_impl_params_are_constrained(
             }
         };
         if err {
-            let const_param_note =
-                matches!(param.kind, ty::GenericParamDefKind::Const { .. }).then_some(());
+            let const_param_note = matches!(param.kind, ty::GenericParamDefKind::Const { .. });
             let mut diag = tcx.dcx().create_err(UnconstrainedGenericParameter {
                 span: tcx.def_span(param.def_id),
                 param_name: param.name,

compiler/rustc_hir_typeck/src/cast.rs

@@ -505,7 +505,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                     span: self.span,
                     expr_ty: self.expr_ty,
                     cast_ty: fcx.ty_to_string(self.cast_ty),
-                    teach: fcx.tcx.sess.teach(E0607).then_some(()),
+                    teach: fcx.tcx.sess.teach(E0607),
                 });
             }
             CastError::IntToFatCast(known_metadata) => {

compiler/rustc_hir_typeck/src/errors.rs

@@ -706,7 +706,7 @@ pub(crate) struct CastThinPointerToFatPointer<'tcx> {
     pub expr_ty: Ty<'tcx>,
     pub cast_ty: String,
     #[note(hir_typeck_teach_help)]
-    pub(crate) teach: Option<()>,
+    pub(crate) teach: bool,
 }
 
 #[derive(Diagnostic)]
@@ -720,7 +720,7 @@ pub(crate) struct PassToVariadicFunction<'tcx, 'a> {
     pub sugg_span: Option<Span>,
     pub replace: String,
     #[help]
-    pub help: Option<()>,
+    pub help: bool,
     #[note(hir_typeck_teach_help)]
-    pub(crate) teach: Option<()>,
+    pub(crate) teach: bool,
 }

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -406,9 +406,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ) {
                     let (sugg_span, replace, help) =
                         if let Ok(snippet) = sess.source_map().span_to_snippet(span) {
-                            (Some(span), format!("{snippet} as {cast_ty}"), None)
+                            (Some(span), format!("{snippet} as {cast_ty}"), false)
                         } else {
-                            (None, "".to_string(), Some(()))
+                            (None, "".to_string(), true)
                         };
 
                     sess.dcx().emit_err(errors::PassToVariadicFunction {
@@ -418,7 +418,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         help,
                         replace,
                         sugg_span,
-                        teach: sess.teach(E0617).then_some(()),
+                        teach: sess.teach(E0617),
                     });
                 }
 

compiler/rustc_incremental/src/errors.rs

@@ -189,10 +189,10 @@ pub struct CreateLock<'a> {
     pub lock_err: std::io::Error,
     pub session_dir: &'a Path,
     #[note(incremental_lock_unsupported)]
-    pub is_unsupported_lock: Option<()>,
+    pub is_unsupported_lock: bool,
     #[help(incremental_cargo_help_1)]
     #[help(incremental_cargo_help_2)]
-    pub is_cargo: Option<()>,
+    pub is_cargo: bool,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_incremental/src/persist/fs.rs

@@ -486,12 +486,12 @@ fn lock_directory(
         // the lock should be exclusive
         Ok(lock) => Ok((lock, lock_file_path)),
         Err(lock_err) => {
-            let is_unsupported_lock = flock::Lock::error_unsupported(&lock_err).then_some(());
+            let is_unsupported_lock = flock::Lock::error_unsupported(&lock_err);
             Err(sess.dcx().emit_err(errors::CreateLock {
                 lock_err,
                 session_dir,
                 is_unsupported_lock,
-                is_cargo: rustc_session::utils::was_invoked_from_cargo().then_some(()),
+                is_cargo: rustc_session::utils::was_invoked_from_cargo(),
             }))
         }
     }

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)]
@@ -756,15 +756,15 @@ 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)]
     AssignToRef {
         #[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,