Mark ErrorGuaranteed constructor as deprecated so people don't use it

compiler/rustc_driver_impl/src/lib.rs

@@ -1178,6 +1178,7 @@ fn extra_compiler_flags() -> Option<(Vec<String>, bool)> {
 pub fn catch_fatal_errors<F: FnOnce() -> R, R>(f: F) -> Result<R, ErrorGuaranteed> {
     catch_unwind(panic::AssertUnwindSafe(f)).map_err(|value| {
         if value.is::<rustc_errors::FatalErrorMarker>() {
+            #[allow(deprecated)]
             ErrorGuaranteed::unchecked_claim_error_was_emitted()
         } else {
             panic::resume_unwind(value);

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -192,6 +192,7 @@ impl EmissionGuarantee for ErrorGuaranteed {
                      became non-error ({:?}), after original `.emit()`",
                     db.inner.diagnostic.level,
                 );
+                #[allow(deprecated)]
                 ErrorGuaranteed::unchecked_claim_error_was_emitted()
             }
         }

compiler/rustc_errors/src/lib.rs

@@ -1069,26 +1069,29 @@ impl Handler {
     }
 
     pub fn has_errors(&self) -> Option<ErrorGuaranteed> {
-        self.inner.borrow().has_errors().then(ErrorGuaranteed::unchecked_claim_error_was_emitted)
+        self.inner.borrow().has_errors().then(|| {
+            #[allow(deprecated)]
+            ErrorGuaranteed::unchecked_claim_error_was_emitted()
+        })
     }
 
     pub fn has_errors_or_lint_errors(&self) -> Option<ErrorGuaranteed> {
-        self.inner
-            .borrow()
-            .has_errors_or_lint_errors()
-            .then(ErrorGuaranteed::unchecked_claim_error_was_emitted)
+        self.inner.borrow().has_errors_or_lint_errors().then(|| {
+            #[allow(deprecated)]
+            ErrorGuaranteed::unchecked_claim_error_was_emitted()
+        })
     }
     pub fn has_errors_or_delayed_span_bugs(&self) -> Option<ErrorGuaranteed> {
-        self.inner
-            .borrow()
-            .has_errors_or_delayed_span_bugs()
-            .then(ErrorGuaranteed::unchecked_claim_error_was_emitted)
+        self.inner.borrow().has_errors_or_delayed_span_bugs().then(|| {
+            #[allow(deprecated)]
+            ErrorGuaranteed::unchecked_claim_error_was_emitted()
+        })
     }
     pub fn is_compilation_going_to_fail(&self) -> Option<ErrorGuaranteed> {
-        self.inner
-            .borrow()
-            .is_compilation_going_to_fail()
-            .then(ErrorGuaranteed::unchecked_claim_error_was_emitted)
+        self.inner.borrow().is_compilation_going_to_fail().then(|| {
+            #[allow(deprecated)]
+            ErrorGuaranteed::unchecked_claim_error_was_emitted()
+        })
     }
 
     pub fn print_error_count(&self, registry: &Registry) {
@@ -1333,6 +1336,7 @@ impl HandlerInner {
                 .push(DelayedDiagnostic::with_backtrace(diagnostic.clone(), backtrace));
 
             if !self.flags.report_delayed_bugs {
+                #[allow(deprecated)]
                 return Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
             }
         }
@@ -1411,7 +1415,10 @@ impl HandlerInner {
                     self.bump_err_count();
                 }
 
+                #[allow(deprecated)]
+                {
                     guaranteed = Some(ErrorGuaranteed::unchecked_claim_error_was_emitted());
+                }
             } else {
                 self.bump_warn_count();
             }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -854,9 +854,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let result = self
             .resolve_fully_qualified_call(span, item_name, ty.normalized, qself.span, hir_id)
             .or_else(|error| {
+                let guar = self
+                    .tcx
+                    .sess
+                    .delay_span_bug(span, "method resolution should've emitted an error");
                 let result = match error {
                     method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
-                    _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
+                    _ => Err(guar),
                 };
 
                 // If we have a path like `MyTrait::missing_method`, then don't register

compiler/rustc_span/src/lib.rs

@@ -2200,6 +2200,7 @@ pub struct ErrorGuaranteed(());
 impl ErrorGuaranteed {
     /// To be used only if you really know what you are doing... ideally, we would find a way to
     /// eliminate all calls to this method.
+    #[deprecated = "`Session::delay_span_bug` should be preferred over this function"]
     pub fn unchecked_claim_error_was_emitted() -> Self {
         ErrorGuaranteed(())
     }

src/librustdoc/lib.rs

@@ -172,7 +172,11 @@ pub fn main() {
 
     let exit_code = rustc_driver::catch_with_exit_code(|| match get_args() {
         Some(args) => main_args(&args),
-        _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
+        _ =>
+        {
+            #[allow(deprecated)]
+            Err(ErrorGuaranteed::unchecked_claim_error_was_emitted())
+        }
     });
     process::exit(exit_code);
 }
@@ -725,6 +729,7 @@ fn main_args(at_args: &[String]) -> MainResult {
             return if code == 0 {
                 Ok(())
             } else {
+                #[allow(deprecated)]
                 Err(ErrorGuaranteed::unchecked_claim_error_was_emitted())
             };
         }