From ed468eebf6e852b80eeed6997c67444268795faa Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 30 Apr 2023 21:52:35 +0000
Subject: [PATCH] Encode def span for foreign RPITITs

---
 compiler/rustc_metadata/src/rmeta/encoder.rs      |  3 ++-
 tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs  |  4 ++--
 tests/ui/impl-trait/in-trait/foreign-dyn-error.rs |  8 ++++++++
 .../impl-trait/in-trait/foreign-dyn-error.stderr  | 15 +++++++++++++++
 tests/ui/impl-trait/in-trait/foreign.rs           |  9 +++++----
 5 files changed, 32 insertions(+), 7 deletions(-)
 create mode 100644 tests/ui/impl-trait/in-trait/foreign-dyn-error.rs
 create mode 100644 tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr

diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index f5ffdd27cae3f..479bac9b2aaeb 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -837,11 +837,12 @@ fn should_encode_span(def_kind: DefKind) -> bool {
         | DefKind::AnonConst
         | DefKind::InlineConst
         | DefKind::OpaqueTy
+        | DefKind::ImplTraitPlaceholder
         | DefKind::Field
         | DefKind::Impl { .. }
         | DefKind::Closure
         | DefKind::Generator => true,
-        DefKind::ForeignMod | DefKind::ImplTraitPlaceholder | DefKind::GlobalAsm => false,
+        DefKind::ForeignMod | DefKind::GlobalAsm => false,
     }
 }
 
diff --git a/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs b/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
index ffeabe5c2edab..776006124dccf 100644
--- a/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
+++ b/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
@@ -5,10 +5,10 @@
 use std::ops::Deref;
 
 pub trait Foo {
-    fn bar() -> impl Deref<Target = impl Sized>;
+    fn bar(self) -> impl Deref<Target = impl Sized>;
 }
 
 pub struct Foreign;
 impl Foo for Foreign {
-    fn bar() -> &'static () { &() }
+    fn bar(self) -> &'static () { &() }
 }
diff --git a/tests/ui/impl-trait/in-trait/foreign-dyn-error.rs b/tests/ui/impl-trait/in-trait/foreign-dyn-error.rs
new file mode 100644
index 0000000000000..ecb5e62c433a0
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/foreign-dyn-error.rs
@@ -0,0 +1,8 @@
+// aux-build: rpitit.rs
+
+extern crate rpitit;
+
+fn main() {
+    let _: &dyn rpitit::Foo = todo!();
+    //~^ ERROR the trait `Foo` cannot be made into an object
+}
diff --git a/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr b/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
new file mode 100644
index 0000000000000..6eef392c05f01
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
@@ -0,0 +1,15 @@
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/foreign-dyn-error.rs:6:12
+   |
+LL |     let _: &dyn rpitit::Foo = todo!();
+   |            ^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/auxiliary/rpitit.rs:8:21
+   |
+LL |     fn bar(self) -> impl Deref<Target = impl Sized>;
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait cannot be made into an object because method `bar` references an `impl Trait` type in its return type
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0038`.
diff --git a/tests/ui/impl-trait/in-trait/foreign.rs b/tests/ui/impl-trait/in-trait/foreign.rs
index f4972d948b246..98417b343a11e 100644
--- a/tests/ui/impl-trait/in-trait/foreign.rs
+++ b/tests/ui/impl-trait/in-trait/foreign.rs
@@ -5,17 +5,18 @@
 
 extern crate rpitit;
 
+use rpitit::{Foo, Foreign};
 use std::sync::Arc;
 
 // Implement an RPITIT from another crate.
 struct Local;
-impl rpitit::Foo for Local {
-    fn bar() -> Arc<String> { Arc::new(String::new()) }
+impl Foo for Local {
+    fn bar(self) -> Arc<String> { Arc::new(String::new()) }
 }
 
 fn main() {
     // Witness an RPITIT from another crate.
-    let &() = <rpitit::Foreign as rpitit::Foo>::bar();
+    let &() = Foreign.bar();
 
-    let x: Arc<String> = <Local as rpitit::Foo>::bar();
+    let x: Arc<String> = Local.bar();
 }