From d6de40b536f6d592de3d0a00626a4dc595d40078 Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Thu, 29 Dec 2022 09:53:25 +0000
Subject: [PATCH] Make `is_object_safe` a query and move
 lint_object_unsafe_trait call there

---
 compiler/rustc_middle/src/query/mod.rs        |  3 ++
 compiler/rustc_middle/src/ty/mod.rs           |  4 --
 .../src/traits/object_safety.rs               | 46 +++++++++++++------
 3 files changed, 35 insertions(+), 18 deletions(-)

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index e4df309e0089..1b9298e82d6b 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1274,6 +1274,9 @@ rustc_queries! {
     query object_safety_violations(trait_id: DefId) -> &'tcx [traits::ObjectSafetyViolation] {
         desc { |tcx| "determining object safety of trait `{}`", tcx.def_path_str(trait_id) }
     }
+    query is_object_safe(trait_id: DefId) -> bool {
+        desc { |tcx| "determining object safety of trait `{}`", tcx.def_path_str(trait_id) }
+    }
 
     /// Gets the ParameterEnvironment for a given item; this environment
     /// will be in "user-facing" mode, meaning that it is suitable for
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 4af29fcbfb58..8e936174c8be 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2471,10 +2471,6 @@ impl<'tcx> TyCtxt<'tcx> {
             }
     }
 
-    pub fn is_object_safe(self, key: DefId) -> bool {
-        self.object_safety_violations(key).is_empty()
-    }
-
     #[inline]
     pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
         matches!(
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 55c2f7e2e358..a5447c012f06 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -62,6 +62,37 @@ fn object_safety_violations(tcx: TyCtxt<'_>, trait_def_id: DefId) -> &'_ [Object
     )
 }
 
+fn is_object_safe(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {
+    let violations = tcx.object_safety_violations(trait_def_id);
+
+    if violations.is_empty() {
+        return true;
+    }
+
+    // If the trait contains any other violations, then let the error reporting path
+    // report it instead of emitting a warning here.
+    if violations.iter().all(|violation| {
+        matches!(
+            violation,
+            ObjectSafetyViolation::Method(_, MethodViolationCode::WhereClauseReferencesSelf, _)
+        )
+    }) {
+        for violation in violations {
+            if let ObjectSafetyViolation::Method(
+                _,
+                MethodViolationCode::WhereClauseReferencesSelf,
+                span,
+            ) = violation
+            {
+                lint_object_unsafe_trait(tcx, *span, trait_def_id, &violation);
+            }
+        }
+        return true;
+    }
+
+    false
+}
+
 /// We say a method is *vtable safe* if it can be invoked on a trait
 /// object. Note that object-safe traits can have some
 /// non-vtable-safe methods, so long as they require `Self: Sized` or
@@ -93,19 +124,6 @@ fn object_safety_violations_for_trait(
             object_safety_violation_for_method(tcx, trait_def_id, &item)
                 .map(|(code, span)| ObjectSafetyViolation::Method(item.name, code, span))
         })
-        .filter(|violation| {
-            if let ObjectSafetyViolation::Method(
-                _,
-                MethodViolationCode::WhereClauseReferencesSelf,
-                span,
-            ) = violation
-            {
-                lint_object_unsafe_trait(tcx, *span, trait_def_id, &violation);
-                false
-            } else {
-                true
-            }
-        })
         .collect();
 
     // Check the trait itself.
@@ -866,5 +884,5 @@ pub fn contains_illegal_impl_trait_in_trait<'tcx>(
 }
 
 pub fn provide(providers: &mut ty::query::Providers) {
-    *providers = ty::query::Providers { object_safety_violations, ..*providers };
+    *providers = ty::query::Providers { object_safety_violations, is_object_safe, ..*providers };
 }