From 223a2ee3061a4bfe31df8aee70c682618ef28fe1 Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Fri, 17 Jan 2020 20:11:51 +0000
Subject: [PATCH] Add fast path to eq_opaque_type_and_type

---
 src/librustc/ty/flags.rs                        |  2 +-
 src/librustc/ty/fold.rs                         |  3 +++
 src/librustc/ty/mod.rs                          |  5 ++++-
 src/librustc/ty/util.rs                         |  2 +-
 src/librustc_mir/borrow_check/type_check/mod.rs | 16 ++++++++++++++++
 5 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/src/librustc/ty/flags.rs b/src/librustc/ty/flags.rs
index 4a4280ba7dc..4546eadc6e6 100644
--- a/src/librustc/ty/flags.rs
+++ b/src/librustc/ty/flags.rs
@@ -138,7 +138,7 @@ impl FlagComputation {
             }
 
             &ty::Opaque(_, substs) => {
-                self.add_flags(TypeFlags::HAS_PROJECTION);
+                self.add_flags(TypeFlags::HAS_PROJECTION | TypeFlags::HAS_TY_OPAQUE);
                 self.add_substs(substs);
             }
 
diff --git a/src/librustc/ty/fold.rs b/src/librustc/ty/fold.rs
index 5ff0d04c1ed..3212bc72417 100644
--- a/src/librustc/ty/fold.rs
+++ b/src/librustc/ty/fold.rs
@@ -78,6 +78,9 @@ pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
     fn has_projections(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_PROJECTION)
     }
+    fn has_opaque_types(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_TY_OPAQUE)
+    }
     fn references_error(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_ERR)
     }
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 6d36116d782..45ea05efd4a 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -481,6 +481,8 @@ bitflags! {
 
         const HAS_CT_INFER       = 1 << 14;
         const HAS_CT_PLACEHOLDER = 1 << 15;
+        /// Does this have any [Opaque] types.
+        const HAS_TY_OPAQUE      = 1 << 16;
 
         const NEEDS_SUBST        = TypeFlags::HAS_PARAMS.bits |
                                    TypeFlags::HAS_RE_EARLY_BOUND.bits;
@@ -503,7 +505,8 @@ bitflags! {
                                   TypeFlags::HAS_RE_ERASED.bits |
                                   TypeFlags::HAS_TY_PLACEHOLDER.bits |
                                   TypeFlags::HAS_CT_INFER.bits |
-                                  TypeFlags::HAS_CT_PLACEHOLDER.bits;
+                                  TypeFlags::HAS_CT_PLACEHOLDER.bits |
+                                  TypeFlags::HAS_TY_OPAQUE.bits;
     }
 }
 
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index db7b8d8cfd9..f3c3d04931a 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -615,7 +615,7 @@ impl<'tcx> TyCtxt<'tcx> {
             fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
                 if let ty::Opaque(def_id, substs) = t.kind {
                     self.expand_opaque_ty(def_id, substs).unwrap_or(t)
-                } else if t.has_projections() {
+                } else if t.has_opaque_types() {
                     t.super_fold_with(self)
                 } else {
                     t
diff --git a/src/librustc_mir/borrow_check/type_check/mod.rs b/src/librustc_mir/borrow_check/type_check/mod.rs
index 2a2d8642760..88fe6d1a3a4 100644
--- a/src/librustc_mir/borrow_check/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/type_check/mod.rs
@@ -1196,6 +1196,22 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
              anon_ty={:?})",
             revealed_ty, anon_ty
         );
+
+        // Fast path for the common case.
+        if !anon_ty.has_opaque_types() {
+            if let Err(terr) = self.eq_types(anon_ty, revealed_ty, locations, category) {
+                span_mirbug!(
+                    self,
+                    locations,
+                    "eq_opaque_type_and_type: `{:?}=={:?}` failed with `{:?}`",
+                    revealed_ty,
+                    anon_ty,
+                    terr
+                );
+            }
+            return Ok(());
+        }
+
         let infcx = self.infcx;
         let tcx = infcx.tcx;
         let param_env = self.param_env;