Suppress MIR comments of Unit type

Author: tesuji

src/librustc_mir/util/pretty.rs

@@ -389,6 +389,8 @@ impl Visitor<'tcx> for ExtraComments<'tcx> {
         let Constant { span, user_ty, literal } = constant;
         match literal.ty.kind {
             ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char => {}
+            // Unit type
+            ty::Tuple(tys) if tys.is_empty() => {}
             _ => {
                 self.push("mir::Constant");
                 self.push(&format!("+ span: {}", self.tcx.sess.source_map().span_to_string(*span)));
@@ -405,6 +407,8 @@ impl Visitor<'tcx> for ExtraComments<'tcx> {
         let ty::Const { ty, val, .. } = constant;
         match ty.kind {
             ty::Int(_) | ty::Uint(_) | ty::Bool | ty::Char => {}
+            // Unit type
+            ty::Tuple(tys) if tys.is_empty() => {}
             ty::FnDef(..) => {}
             _ => {
                 self.push("ty::Const");

src/test/mir-opt/address_of.address_of_reborrow.SimplifyCfg-initial.after.mir

@@ -287,12 +287,6 @@ fn address_of_reborrow() -> () {
         FakeRead(ForLet, _47);           // scope 13 at $DIR/address-of.rs:36:9: 36:10
         AscribeUserType(_47, o, UserTypeProjection { base: UserType(29), projs: [] }); // scope 13 at $DIR/address-of.rs:36:12: 36:22
         _0 = const ();                   // scope 0 at $DIR/address-of.rs:3:26: 37:2
-                                         // ty::Const
-                                         // + ty: ()
-                                         // + val: Value(Scalar(<ZST>))
-                                         // mir::Constant
-                                         // + span: $DIR/address-of.rs:3:26: 37:2
-                                         // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
         StorageDead(_47);                // scope 13 at $DIR/address-of.rs:37:1: 37:2
         StorageDead(_45);                // scope 12 at $DIR/address-of.rs:37:1: 37:2
         StorageDead(_44);                // scope 11 at $DIR/address-of.rs:37:1: 37:2