rustc_error: make ErrorReported impossible to construct

There are a few places were we have to construct it, though, and a few
places that are more invasive to change. To do this, we create a
constructor with a long obvious name.

compiler/rustc_mir_transform/src/check_const_item_mutation.rs

@@ -64,7 +64,7 @@ impl<'tcx> ConstMutationChecker<'_, 'tcx> {
         place: &Place<'tcx>,
         const_item: DefId,
         location: Location,
-        decorate: impl for<'b> FnOnce(LintDiagnosticBuilder<'b>) -> DiagnosticBuilder<'b, ()>,
+        decorate: impl for<'b> FnOnce(LintDiagnosticBuilder<'b, ()>) -> DiagnosticBuilder<'b, ()>,
     ) {
         // Don't lint on borrowing/assigning when a dereference is involved.
         // If we 'leave' the temporary via a dereference, we must
@@ -88,7 +88,7 @@ impl<'tcx> ConstMutationChecker<'_, 'tcx> {
                 |lint| {
                     decorate(lint)
                         .span_note(self.tcx.def_span(const_item), "`const` item defined here")
-                        .emit()
+                        .emit();
                 },
             );
         }

compiler/rustc_mir_transform/src/check_packed_ref.rs

@@ -46,7 +46,7 @@ fn unsafe_derive_on_repr_packed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
              does not derive Copy (error E0133)"
                 .to_string()
         };
-        lint.build(&message).emit()
+        lint.build(&message).emit();
     });
 }
 
@@ -110,7 +110,7 @@ impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> {
                                     reference with a raw pointer and use `read_unaligned`/`write_unaligned` \
                                     (loads and stores via `*p` must be properly aligned even when using raw pointers)"
                                 )
-                                .emit()
+                                .emit();
                         },
                     );
                 }

compiler/rustc_mir_transform/src/const_prop.rs

@@ -538,7 +538,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             self.tcx.struct_span_lint_hir(lint, lint_root, source_info.span, |lint| {
                 let mut err = lint.build(message);
                 err.span_label(source_info.span, format!("{:?}", panic));
-                err.emit()
+                err.emit();
             });
         }
     }