Rollup merge of #129344 - compiler-errors:less-option-unit-diagnostics, r=jieyouxu

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

We originally only supported `Option<()>` for optional notes/labels, but we now support `bool`. Let's use that, since it usually leads to more readable code.

I'm not removing the support from the derive macro, though I guess we could error on it... 🤔

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -793,7 +793,7 @@ impl UnsafeOpKind {
                         missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
-                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    note: !build_enabled.is_empty(),
                     build_target_features: DiagArgValue::StrListSepByAnd(
                         build_enabled
                             .iter()
@@ -958,7 +958,7 @@ impl UnsafeOpKind {
                         missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
-                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    note: !build_enabled.is_empty(),
                     build_target_features: DiagArgValue::StrListSepByAnd(
                         build_enabled
                             .iter()
@@ -977,7 +977,7 @@ impl UnsafeOpKind {
                         missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
                     ),
                     missing_target_features_count: missing.len(),
-                    note: if build_enabled.is_empty() { None } else { Some(()) },
+                    note: !build_enabled.is_empty(),
                     build_target_features: DiagArgValue::StrListSepByAnd(
                         build_enabled
                             .iter()

compiler/rustc_mir_build/src/errors.rs

@@ -161,7 +161,7 @@ pub(crate) struct UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe {
     pub(crate) missing_target_features: DiagArgValue,
     pub(crate) missing_target_features_count: usize,
     #[note]
-    pub(crate) note: Option<()>,
+    pub(crate) note: bool,
     pub(crate) build_target_features: DiagArgValue,
     pub(crate) build_target_features_count: usize,
     #[subdiagnostic]
@@ -413,7 +413,7 @@ pub(crate) struct CallToFunctionWithRequiresUnsafe {
     pub(crate) missing_target_features: DiagArgValue,
     pub(crate) missing_target_features_count: usize,
     #[note]
-    pub(crate) note: Option<()>,
+    pub(crate) note: bool,
     pub(crate) build_target_features: DiagArgValue,
     pub(crate) build_target_features_count: usize,
     #[subdiagnostic]
@@ -431,7 +431,7 @@ pub(crate) struct CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     pub(crate) missing_target_features: DiagArgValue,
     pub(crate) missing_target_features_count: usize,
     #[note]
-    pub(crate) note: Option<()>,
+    pub(crate) note: bool,
     pub(crate) build_target_features: DiagArgValue,
     pub(crate) build_target_features_count: usize,
     #[subdiagnostic]
@@ -621,7 +621,7 @@ pub(crate) struct LowerRangeBoundMustBeLessThanOrEqualToUpper {
     #[label]
     pub(crate) span: Span,
     #[note(mir_build_teach_note)]
-    pub(crate) teach: Option<()>,
+    pub(crate) teach: bool,
 }
 
 #[derive(Diagnostic)]
@@ -863,7 +863,7 @@ pub(crate) struct PatternNotCovered<'s, 'tcx> {
     #[subdiagnostic]
     pub(crate) adt_defined_here: Option<AdtDefinedHere<'tcx>>,
     #[note(mir_build_privately_uninhabited)]
-    pub(crate) witness_1_is_privately_uninhabited: Option<()>,
+    pub(crate) witness_1_is_privately_uninhabited: bool,
     #[note(mir_build_pattern_ty)]
     pub(crate) _p: (),
     pub(crate) pattern_ty: Ty<'tcx>,

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -718,7 +718,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
             uncovered: Uncovered::new(pat.span, &cx, witnesses),
             inform,
             interpreted_as_const,
-            witness_1_is_privately_uninhabited: witness_1_is_privately_uninhabited.then_some(()),
+            witness_1_is_privately_uninhabited,
             _p: (),
             pattern_ty,
             let_suggestion,

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -256,7 +256,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                     RangeEnd::Included => {
                         self.tcx.dcx().emit_err(LowerRangeBoundMustBeLessThanOrEqualToUpper {
                             span,
-                            teach: self.tcx.sess.teach(E0030).then_some(()),
+                            teach: self.tcx.sess.teach(E0030),
                         })
                     }
                     RangeEnd::Excluded => {