Diagnostic cleanups

- `emitted_at` isn't used outside the crate.
- `code` and `messages` are public fields, so there's no point have
  trivial getters/setters for them.
- `suggestions` is public, so the comment about "functionality on
  `Diagnostic`" isn't needed.

compiler/rustc_codegen_llvm/src/errors.rs

@@ -102,7 +102,7 @@ pub(crate) struct ParseTargetMachineConfig<'a>(pub LlvmError<'a>);
 impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for ParseTargetMachineConfig<'_> {
     fn into_diagnostic(self, dcx: &'_ DiagCtxt, level: Level) -> DiagnosticBuilder<'_, G> {
         let diag: DiagnosticBuilder<'_, G> = self.0.into_diagnostic(dcx, level);
-        let (message, _) = diag.messages().first().expect("`LlvmError` with no message");
+        let (message, _) = diag.messages.first().expect("`LlvmError` with no message");
         let message = dcx.eagerly_translate_to_string(message.clone(), diag.args());
 
         DiagnosticBuilder::new(dcx, level, fluent::codegen_llvm_parse_target_machine_config)

compiler/rustc_errors/src/diagnostic.rs

@@ -116,7 +116,7 @@ pub struct Diagnostic {
 
     /// With `-Ztrack_diagnostics` enabled,
     /// we print where in rustc this error was emitted.
-    pub emitted_at: DiagnosticLocation,
+    pub(crate) emitted_at: DiagnosticLocation,
 }
 
 #[derive(Clone, Debug, Encodable, Decodable)]
@@ -206,9 +206,6 @@ impl StringPart {
     }
 }
 
-// Note: most of these methods are setters that return `&mut Self`. The small
-// number of simple getter functions all have `get_` prefixes to distinguish
-// them from the setters.
 impl Diagnostic {
     #[track_caller]
     pub fn new<M: Into<DiagnosticMessage>>(level: Level, message: M) -> Self {
@@ -889,15 +886,6 @@ impl Diagnostic {
         self
     }
 
-    pub fn clear_code(&mut self) -> &mut Self {
-        self.code = None;
-        self
-    }
-
-    pub fn get_code(&self) -> Option<ErrCode> {
-        self.code
-    }
-
     pub fn primary_message(&mut self, msg: impl Into<DiagnosticMessage>) -> &mut Self {
         self.messages[0] = (msg.into(), Style::NoStyle);
         self
@@ -923,10 +911,6 @@ impl Diagnostic {
         self.args = args;
     }
 
-    pub fn messages(&self) -> &[(DiagnosticMessage, Style)] {
-        &self.messages
-    }
-
     /// Helper function that takes a `SubdiagnosticMessage` and returns a `DiagnosticMessage` by
     /// combining it with the primary message of the diagnostic (if translatable, otherwise it just
     /// passes the user's string along).

compiler/rustc_errors/src/lib.rs

@@ -1422,7 +1422,7 @@ impl DiagCtxtInner {
                     &mut out,
                     "delayed span bug: {}\n{}\n",
                     bug.inner
-                        .messages()
+                        .messages
                         .iter()
                         .filter_map(|(msg, _)| msg.as_str())
                         .collect::<String>(),

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -590,7 +590,6 @@ fn infer_placeholder_type<'a>(
 
                 // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
                 // We are typeck and have the real type, so remove that and suggest the actual type.
-                // FIXME(eddyb) this looks like it should be functionality on `Diagnostic`.
                 if let Ok(suggestions) = &mut err.suggestions {
                     suggestions.clear();
                 }

compiler/rustc_hir_typeck/src/pat.rs

@@ -576,7 +576,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if (lhs, rhs).references_error() {
             err.downgrade_to_delayed_bug();
         }
-        if self.tcx.sess.teach(err.get_code().unwrap()) {
+        if self.tcx.sess.teach(err.code.unwrap()) {
             err.note(
                 "In a match expression, only numbers and characters can be matched \
                     against a range. This is because the compiler checks that the range \
@@ -847,7 +847,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 type_str
             );
             err.span_label(span, format!("type `{type_str}` cannot be dereferenced"));
-            if self.tcx.sess.teach(err.get_code().unwrap()) {
+            if self.tcx.sess.teach(err.code.unwrap()) {
                 err.note(CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ);
             }
             return Err(err.emit());
@@ -1669,7 +1669,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
         }
-        if tcx.sess.teach(err.get_code().unwrap()) {
+        if tcx.sess.teach(err.code.unwrap()) {
             err.note(
                 "This error indicates that a struct pattern attempted to \
                  extract a nonexistent field from a struct. Struct fields \

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -195,7 +195,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             }
                         }
                         diag.help("type parameters must be constrained to match other types");
-                        if tcx.sess.teach(diag.get_code().unwrap()) {
+                        if tcx.sess.teach(diag.code.unwrap()) {
                             diag.help(
                                 "given a type parameter `T` and a method `foo`:
 ```
@@ -678,7 +678,7 @@ impl<T> Trait<T> for X {
                  https://doc.rust-lang.org/book/ch19-03-advanced-traits.html",
             );
         }
-        if tcx.sess.teach(diag.get_code().unwrap()) {
+        if tcx.sess.teach(diag.code.unwrap()) {
             diag.help(
                 "given an associated type `T` and a method `foo`:
 ```

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -2717,7 +2717,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             let (trait_name, trait_verb) =
                 if name == sym::Send { ("`Send`", "sent") } else { ("`Sync`", "shared") };
 
-            err.clear_code();
+            err.code = None;
             err.primary_message(format!(
                 "{future_or_coroutine} cannot be {trait_verb} between threads safely"
             ));