rustc_errors: remove struct_dummy.

compiler/rustc_errors/src/lib.rs

@@ -622,14 +622,6 @@ impl Handler {
         self.inner.borrow_mut().emit_stashed_diagnostics();
     }
 
-    /// Construct a dummy builder with `Level::Cancelled`.
-    ///
-    /// Using this will neither report anything to the user (e.g. a warning),
-    /// nor will compilation cancel as a result.
-    pub fn struct_dummy(&self) -> DiagnosticBuilder<'_> {
-        DiagnosticBuilder::new(self, Level::Cancelled, "")
-    }
-
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
     ///
     /// Attempting to `.emit()` the builder will only emit if either:

compiler/rustc_infer/src/infer/mod.rs

@@ -1482,12 +1482,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let actual_ty = self.resolve_vars_if_possible(actual_ty);
         debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
 
+        let mut err = mk_diag(self.ty_to_string(actual_ty));
+
         // Don't report an error if actual type is `Error`.
         if actual_ty.references_error() {
-            return self.tcx.sess.diagnostic().struct_dummy();
+            err.downgrade_to_delayed_bug();
         }
 
-        mk_diag(self.ty_to_string(actual_ty))
+        err
     }
 
     pub fn report_mismatched_types(

compiler/rustc_parse/src/parser/expr.rs

@@ -1622,9 +1622,11 @@ impl<'a> Parser<'a> {
                 };
                 if let Some(expr) = expr {
                     if matches!(expr.kind, ExprKind::Err) {
-                        self.diagnostic()
-                            .delay_span_bug(self.token.span, &"invalid interpolated expression");
-                        return self.diagnostic().struct_dummy();
+                        let mut err = self
+                            .diagnostic()
+                            .struct_span_err(self.token.span, &"invalid interpolated expression");
+                        err.downgrade_to_delayed_bug();
+                        return err;
                     }
                 }
             }

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -268,7 +268,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         (None, true) => "variant",
                     }
                 };
-                let mut err = if !actual.references_error() {
+                // FIXME(eddyb) this intendation is probably unnecessary.
+                let mut err = {
                     // Suggest clamping down the type if the method that is being attempted to
                     // be used exists at all, and the type is an ambiguous numeric type
                     // ({integer}/{float}).
@@ -461,10 +462,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                         err
                     }
-                } else {
-                    tcx.sess.diagnostic().struct_dummy()
                 };
 
+                if actual.references_error() {
+                    err.downgrade_to_delayed_bug();
+                }
+
                 if let Some(def) = actual.ty_adt_def() {
                     if let Some(full_sp) = tcx.hir().span_if_local(def.did) {
                         let def_sp = tcx.sess.source_map().guess_head_span(full_sp);

compiler/rustc_typeck/src/check/mod.rs

@@ -139,11 +139,13 @@ pub use self::Expectation::*;
 #[macro_export]
 macro_rules! type_error_struct {
     ($session:expr, $span:expr, $typ:expr, $code:ident, $($message:tt)*) => ({
+        let mut err = rustc_errors::struct_span_err!($session, $span, $code, $($message)*);
+
         if $typ.references_error() {
-            $session.diagnostic().struct_dummy()
-        } else {
-            rustc_errors::struct_span_err!($session, $span, $code, $($message)*)
+            err.downgrade_to_delayed_bug();
         }
+
+        err
     })
 }
 

compiler/rustc_typeck/src/structured_errors/missing_cast_for_variadic_arg.rs

@@ -21,15 +21,15 @@ impl<'tcx> StructuredDiagnostic<'tcx> for MissingCastForVariadicArg<'tcx> {
     }
 
     fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
-        let mut err = if self.ty.references_error() {
-            self.sess.diagnostic().struct_dummy()
-        } else {
-            self.sess.struct_span_fatal_with_code(
-                self.span,
-                &format!("can't pass `{}` to variadic function", self.ty),
-                self.code(),
-            )
-        };
+        let mut err = self.sess.struct_span_fatal_with_code(
+            self.span,
+            &format!("can't pass `{}` to variadic function", self.ty),
+            self.code(),
+        );
+
+        if self.ty.references_error() {
+            err.downgrade_to_delayed_bug();
+        }
 
         if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.span) {
             err.span_suggestion(

compiler/rustc_typeck/src/structured_errors/sized_unsized_cast.rs

@@ -21,18 +21,20 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> {
     }
 
     fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
+        let mut err = self.sess.struct_span_fatal_with_code(
+            self.span,
+            &format!(
+                "cannot cast thin pointer `{}` to fat pointer `{}`",
+                self.expr_ty, self.cast_ty
+            ),
+            self.code(),
+        );
+
         if self.expr_ty.references_error() {
-            self.sess.diagnostic().struct_dummy()
-        } else {
-            self.sess.struct_span_fatal_with_code(
-                self.span,
-                &format!(
-                    "cannot cast thin pointer `{}` to fat pointer `{}`",
-                    self.expr_ty, self.cast_ty
-                ),
-                self.code(),
-            )
+            err.downgrade_to_delayed_bug();
         }
+
+        err
     }
 
     fn diagnostic_extended(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {