Use a dedicated type instead of a reference for the diagnostic context

This paves the way for tracking more state (e.g. error tainting) in the diagnostic context handle

compiler/rustc_errors/src/lib.rs

@@ -414,6 +414,19 @@ pub struct DiagCtxt {
     inner: Lock<DiagCtxtInner>,
 }
 
+#[derive(Copy, Clone)]
+pub struct DiagCtxtHandle<'a> {
+    dcx: &'a DiagCtxt,
+}
+
+impl<'a> std::ops::Deref for DiagCtxtHandle<'a> {
+    type Target = &'a DiagCtxt;
+
+    fn deref(&self) -> &Self::Target {
+        &self.dcx
+    }
+}
+
 /// This inner struct exists to keep it all behind a single lock;
 /// this is done to prevent possible deadlocks in a multi-threaded compiler,
 /// as well as inconsistent state observation.
@@ -608,7 +621,7 @@ impl DiagCtxt {
     }
 
     pub fn make_silent(
-        &mut self,
+        &self,
         fallback_bundle: LazyFallbackBundle,
         fatal_note: Option<String>,
         emit_fatal_diagnostic: bool,
@@ -623,7 +636,7 @@ impl DiagCtxt {
         });
     }
 
-    fn wrap_emitter<F>(&mut self, f: F)
+    fn wrap_emitter<F>(&self, f: F)
     where
         F: FnOnce(DiagCtxtInner) -> Box<DynEmitter>,
     {
@@ -738,6 +751,12 @@ impl DiagCtxt {
         *fulfilled_expectations = Default::default();
     }
 
+    pub fn handle<'a>(&'a self) -> DiagCtxtHandle<'a> {
+        DiagCtxtHandle { dcx: self }
+    }
+}
+
+impl<'a> DiagCtxtHandle<'a> {
     /// Stashes a diagnostic for possible later improvement in a different,
     /// later stage of the compiler. Possible actions depend on the diagnostic
     /// level:
@@ -745,8 +764,8 @@ impl DiagCtxt {
     /// - Level::Error: immediately counted as an error that has occurred, because it
     ///   is guaranteed to be emitted eventually. Can be later accessed with the
     ///   provided `span` and `key` through
-    ///   [`DiagCtxt::try_steal_modify_and_emit_err`] or
-    ///   [`DiagCtxt::try_steal_replace_and_emit_err`]. These do not allow
+    ///   [`DiagCtxtHandle::try_steal_modify_and_emit_err`] or
+    ///   [`DiagCtxtHandle::try_steal_replace_and_emit_err`]. These do not allow
     ///   cancellation or downgrading of the error. Returns
     ///   `Some(ErrorGuaranteed)`.
     /// - Level::DelayedBug: this does happen occasionally with errors that are
@@ -757,7 +776,7 @@ impl DiagCtxt {
     ///   user-facing error. Returns `Some(ErrorGuaranteed)` as is normal for
     ///   delayed bugs.
     /// - Level::Warning and lower (i.e. !is_error()): can be accessed with the
-    ///   provided `span` and `key` through [`DiagCtxt::steal_non_err()`]. This
+    ///   provided `span` and `key` through [`DiagCtxtHandle::steal_non_err()`]. This
     ///   allows cancelling and downgrading of the diagnostic. Returns `None`.
     pub fn stash_diagnostic(
         &self,
@@ -793,7 +812,7 @@ impl DiagCtxt {
     /// Steal a previously stashed non-error diagnostic with the given `Span`
     /// and [`StashKey`] as the key. Panics if the found diagnostic is an
     /// error.
-    pub fn steal_non_err(&self, span: Span, key: StashKey) -> Option<Diag<'_, ()>> {
+    pub fn steal_non_err(self, span: Span, key: StashKey) -> Option<Diag<'a, ()>> {
         let key = (span.with_parent(None), key);
         // FIXME(#120456) - is `swap_remove` correct?
         let (diag, guar) = self.inner.borrow_mut().stashed_diagnostics.swap_remove(&key)?;
@@ -807,7 +826,7 @@ impl DiagCtxt {
     /// no matching diagnostic is found. Panics if the found diagnostic's level
     /// isn't `Level::Error`.
     pub fn try_steal_modify_and_emit_err<F>(
-        &self,
+        self,
         span: Span,
         key: StashKey,
         mut modify_err: F,
@@ -833,7 +852,7 @@ impl DiagCtxt {
     /// [`StashKey`] as the key, cancels it if found, and emits `new_err`.
     /// Panics if the found diagnostic's level isn't `Level::Error`.
     pub fn try_steal_replace_and_emit_err(
-        &self,
+        self,
         span: Span,
         key: StashKey,
         new_err: Diag<'_>,
@@ -1106,18 +1125,18 @@ impl DiagCtxt {
 //
 // Functions beginning with `struct_`/`create_` create a diagnostic. Other
 // functions create and emit a diagnostic all in one go.
-impl DiagCtxt {
+impl<'a> DiagCtxtHandle<'a> {
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn struct_bug(&self, msg: impl Into<Cow<'static, str>>) -> Diag<'_, BugAbort> {
+    pub fn struct_bug(self, msg: impl Into<Cow<'static, str>>) -> Diag<'a, BugAbort> {
         Diag::new(self, Bug, msg.into())
     }
 
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn bug(&self, msg: impl Into<Cow<'static, str>>) -> ! {
+    pub fn bug(self, msg: impl Into<Cow<'static, str>>) -> ! {
         self.struct_bug(msg).emit()
     }
 
@@ -1125,111 +1144,108 @@ impl DiagCtxt {
     // user-facing.
     #[track_caller]
     pub fn struct_span_bug(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<Cow<'static, str>>,
-    ) -> Diag<'_, BugAbort> {
+    ) -> Diag<'a, BugAbort> {
         self.struct_bug(msg).with_span(span)
     }
 
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn span_bug(&self, span: impl Into<MultiSpan>, msg: impl Into<Cow<'static, str>>) -> ! {
+    pub fn span_bug(self, span: impl Into<MultiSpan>, msg: impl Into<Cow<'static, str>>) -> ! {
         self.struct_span_bug(span, msg.into()).emit()
     }
 
     #[track_caller]
-    pub fn create_bug<'a>(&'a self, bug: impl Diagnostic<'a, BugAbort>) -> Diag<'a, BugAbort> {
+    pub fn create_bug(self, bug: impl Diagnostic<'a, BugAbort>) -> Diag<'a, BugAbort> {
         bug.into_diag(self, Bug)
     }
 
     #[track_caller]
-    pub fn emit_bug<'a>(&'a self, bug: impl Diagnostic<'a, BugAbort>) -> ! {
+    pub fn emit_bug(self, bug: impl Diagnostic<'a, BugAbort>) -> ! {
         self.create_bug(bug).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_fatal(&self, msg: impl Into<DiagMessage>) -> Diag<'_, FatalAbort> {
+    pub fn struct_fatal(self, msg: impl Into<DiagMessage>) -> Diag<'a, FatalAbort> {
         Diag::new(self, Fatal, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn fatal(&self, msg: impl Into<DiagMessage>) -> ! {
+    pub fn fatal(self, msg: impl Into<DiagMessage>) -> ! {
         self.struct_fatal(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_fatal(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, FatalAbort> {
+    ) -> Diag<'a, FatalAbort> {
         self.struct_fatal(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_fatal(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) -> ! {
+    pub fn span_fatal(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) -> ! {
         self.struct_span_fatal(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_fatal<'a>(
-        &'a self,
-        fatal: impl Diagnostic<'a, FatalAbort>,
-    ) -> Diag<'a, FatalAbort> {
+    pub fn create_fatal(self, fatal: impl Diagnostic<'a, FatalAbort>) -> Diag<'a, FatalAbort> {
         fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalAbort>) -> ! {
+    pub fn emit_fatal(self, fatal: impl Diagnostic<'a, FatalAbort>) -> ! {
         self.create_fatal(fatal).emit()
     }
 
     #[track_caller]
-    pub fn create_almost_fatal<'a>(
-        &'a self,
+    pub fn create_almost_fatal(
+        self,
         fatal: impl Diagnostic<'a, FatalError>,
     ) -> Diag<'a, FatalError> {
         fatal.into_diag(self, Fatal)
     }
 
     #[track_caller]
-    pub fn emit_almost_fatal<'a>(&'a self, fatal: impl Diagnostic<'a, FatalError>) -> FatalError {
+    pub fn emit_almost_fatal(self, fatal: impl Diagnostic<'a, FatalError>) -> FatalError {
         self.create_almost_fatal(fatal).emit()
     }
 
     // FIXME: This method should be removed (every error should have an associated error code).
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_err(&self, msg: impl Into<DiagMessage>) -> Diag<'_> {
+    pub fn struct_err(self, msg: impl Into<DiagMessage>) -> Diag<'a> {
         Diag::new(self, Error, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn err(&self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
+    pub fn err(self, msg: impl Into<DiagMessage>) -> ErrorGuaranteed {
         self.struct_err(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_err(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_> {
+    ) -> Diag<'a> {
         self.struct_err(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn span_err(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
     ) -> ErrorGuaranteed {
@@ -1237,12 +1253,12 @@ impl DiagCtxt {
     }
 
     #[track_caller]
-    pub fn create_err<'a>(&'a self, err: impl Diagnostic<'a>) -> Diag<'a> {
+    pub fn create_err(self, err: impl Diagnostic<'a>) -> Diag<'a> {
         err.into_diag(self, Error)
     }
 
     #[track_caller]
-    pub fn emit_err<'a>(&'a self, err: impl Diagnostic<'a>) -> ErrorGuaranteed {
+    pub fn emit_err(self, err: impl Diagnostic<'a>) -> ErrorGuaranteed {
         self.create_err(err).emit()
     }
 
@@ -1251,7 +1267,7 @@ impl DiagCtxt {
     // No `#[rustc_lint_diagnostics]` and no `impl Into<DiagMessage>` because bug messages aren't
     // user-facing.
     #[track_caller]
-    pub fn delayed_bug(&self, msg: impl Into<Cow<'static, str>>) -> ErrorGuaranteed {
+    pub fn delayed_bug(self, msg: impl Into<Cow<'static, str>>) -> ErrorGuaranteed {
         Diag::<ErrorGuaranteed>::new(self, DelayedBug, msg.into()).emit()
     }
 
@@ -1264,7 +1280,7 @@ impl DiagCtxt {
     // user-facing.
     #[track_caller]
     pub fn span_delayed_bug(
-        &self,
+        self,
         sp: impl Into<MultiSpan>,
         msg: impl Into<Cow<'static, str>>,
     ) -> ErrorGuaranteed {
@@ -1273,45 +1289,45 @@ impl DiagCtxt {
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_warn(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_warn(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Warning, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn warn(&self, msg: impl Into<DiagMessage>) {
+    pub fn warn(self, msg: impl Into<DiagMessage>) {
         self.struct_warn(msg).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_warn(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, ()> {
+    ) -> Diag<'a, ()> {
         self.struct_warn(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_warn(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
+    pub fn span_warn(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
         self.struct_span_warn(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+    pub fn create_warn(self, warning: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
         warning.into_diag(self, Warning)
     }
 
     #[track_caller]
-    pub fn emit_warn<'a>(&'a self, warning: impl Diagnostic<'a, ()>) {
+    pub fn emit_warn(self, warning: impl Diagnostic<'a, ()>) {
         self.create_warn(warning).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_note(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_note(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Note, msg)
     }
 
@@ -1324,54 +1340,50 @@ impl DiagCtxt {
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_span_note(
-        &self,
+        self,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagMessage>,
-    ) -> Diag<'_, ()> {
+    ) -> Diag<'a, ()> {
         self.struct_note(msg).with_span(span)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn span_note(&self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
+    pub fn span_note(self, span: impl Into<MultiSpan>, msg: impl Into<DiagMessage>) {
         self.struct_span_note(span, msg).emit()
     }
 
     #[track_caller]
-    pub fn create_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
+    pub fn create_note(self, note: impl Diagnostic<'a, ()>) -> Diag<'a, ()> {
         note.into_diag(self, Note)
     }
 
     #[track_caller]
-    pub fn emit_note<'a>(&'a self, note: impl Diagnostic<'a, ()>) {
+    pub fn emit_note(self, note: impl Diagnostic<'a, ()>) {
         self.create_note(note).emit()
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_help(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_help(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Help, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_failure_note(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_failure_note(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, FailureNote, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_allow(&self, msg: impl Into<DiagMessage>) -> Diag<'_, ()> {
+    pub fn struct_allow(self, msg: impl Into<DiagMessage>) -> Diag<'a, ()> {
         Diag::new(self, Allow, msg)
     }
 
     #[rustc_lint_diagnostics]
     #[track_caller]
-    pub fn struct_expect(
-        &self,
-        msg: impl Into<DiagMessage>,
-        id: LintExpectationId,
-    ) -> Diag<'_, ()> {
+    pub fn struct_expect(self, msg: impl Into<DiagMessage>, id: LintExpectationId) -> Diag<'a, ()> {
         Diag::new(self, Expect(id), msg)
     }
 }