From 81a583c21e74d600ef8c4b45a3d5088382300e17 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Wed, 3 Aug 2022 22:24:47 +0200
Subject: Try normalizing types without RevealAll in ParamEnv in mir validation

Before, the MIR validator used RevealAll in its ParamEnv for type
checking. This could cause false negatives in some cases due to
RevealAll ParamEnvs not always use all predicates as expected here.

Since some MIR passes like inlining use RevealAll as well, keep using
it in the MIR validator too, but when it fails usign RevealAll, also
try the check without it, to stop false negatives.
---
 .../rustc_const_eval/src/transform/validate.rs     | 28 +++++++++++++++-------
 1 file changed, 20 insertions(+), 8 deletions(-)

(limited to 'compiler/rustc_const_eval')

diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index 45a94972c11..ddde9ff4c02 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -181,16 +181,28 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         if (src, dest).has_opaque_types() {
             return true;
         }
+
+        let try_equal_with_param_env = |param_env| {
+            let src = self.tcx.normalize_erasing_regions(param_env, src);
+            let dest = self.tcx.normalize_erasing_regions(param_env, dest);
+            // Type-changing assignments can happen when subtyping is used. While
+            // all normal lifetimes are erased, higher-ranked types with their
+            // late-bound lifetimes are still around and can lead to type
+            // differences. So we compare ignoring lifetimes.
+            equal_up_to_regions(self.tcx, param_env, src, dest)
+        };
+
         // Normalize projections and things like that.
+        // First, try with reveal_all. This might not work in some cases, as the predicates
+        // can be cleared in reveal_all mode. We try the reveal first anyways as it is used
+        // by some other passes like inlining as well.
         let param_env = self.param_env.with_reveal_all_normalized(self.tcx);
-        let src = self.tcx.normalize_erasing_regions(param_env, src);
-        let dest = self.tcx.normalize_erasing_regions(param_env, dest);
-
-        // Type-changing assignments can happen when subtyping is used. While
-        // all normal lifetimes are erased, higher-ranked types with their
-        // late-bound lifetimes are still around and can lead to type
-        // differences. So we compare ignoring lifetimes.
-        equal_up_to_regions(self.tcx, param_env, src, dest)
+        if try_equal_with_param_env(param_env) {
+            true
+        } else {
+            // If this fails, we can try it without the reveal.
+            try_equal_with_param_env(self.param_env)
+        }
     }
 }
 
-- 
cgit 1.4.1-3-g733a5


From 96d4137deed6c52c6db2dd19568c37d1c160f1e7 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sat, 6 Aug 2022 14:22:57 +0200
Subject: Only normalize once in mir validator typechecker

Before, it called `normalize_erasing_regions` twice since
`equal_up_to_regions` called it as well for both types.
---
 .../rustc_const_eval/src/transform/validate.rs     | 25 +++++++++-------------
 1 file changed, 10 insertions(+), 15 deletions(-)

(limited to 'compiler/rustc_const_eval')

diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index ddde9ff4c02..69113e57bdc 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -182,27 +182,22 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return true;
         }
 
-        let try_equal_with_param_env = |param_env| {
-            let src = self.tcx.normalize_erasing_regions(param_env, src);
-            let dest = self.tcx.normalize_erasing_regions(param_env, dest);
-            // Type-changing assignments can happen when subtyping is used. While
-            // all normal lifetimes are erased, higher-ranked types with their
-            // late-bound lifetimes are still around and can lead to type
-            // differences. So we compare ignoring lifetimes.
-            equal_up_to_regions(self.tcx, param_env, src, dest)
-        };
-
         // Normalize projections and things like that.
+        // Type-changing assignments can happen when subtyping is used. While
+        // all normal lifetimes are erased, higher-ranked types with their
+        // late-bound lifetimes are still around and can lead to type
+        // differences. So we compare ignoring lifetimes.
+
         // First, try with reveal_all. This might not work in some cases, as the predicates
         // can be cleared in reveal_all mode. We try the reveal first anyways as it is used
         // by some other passes like inlining as well.
         let param_env = self.param_env.with_reveal_all_normalized(self.tcx);
-        if try_equal_with_param_env(param_env) {
-            true
-        } else {
-            // If this fails, we can try it without the reveal.
-            try_equal_with_param_env(self.param_env)
+        if equal_up_to_regions(self.tcx, param_env, src, dest) {
+            return true;
         }
+
+        // If this fails, we can try it without the reveal.
+        equal_up_to_regions(self.tcx, self.param_env, src, dest)
     }
 }
 
-- 
cgit 1.4.1-3-g733a5