From 11495decd53fe5a11f376475e92c75df97ea8cbb Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Tue, 11 Jun 2024 06:49:05 +0000
Subject: [PATCH] Add regression test

(cherry picked from commit fe55c0091db4654ad0185831aa3dd110e5e6cd73)
---
 tests/ui/impl-trait/recursive-bound-eval.rs   | 18 ++++++++
 .../ui/impl-trait/recursive-bound-eval.stderr | 42 +++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 tests/ui/impl-trait/recursive-bound-eval.rs
 create mode 100644 tests/ui/impl-trait/recursive-bound-eval.stderr

diff --git a/tests/ui/impl-trait/recursive-bound-eval.rs b/tests/ui/impl-trait/recursive-bound-eval.rs
new file mode 100644
index 000000000000..f992cb3071a9
--- /dev/null
+++ b/tests/ui/impl-trait/recursive-bound-eval.rs
@@ -0,0 +1,18 @@
+pub trait Parser<E> {
+    fn parse(&self) -> E;
+}
+
+impl<E, T: Fn() -> E> Parser<E> for T {
+    fn parse(&self) -> E {
+        self()
+    }
+}
+
+pub fn recursive_fn<E>() -> impl Parser<E> {
+    //~^ ERROR: cycle detected
+    move || recursive_fn().parse()
+    //~^ ERROR: type annotations needed
+    //~| ERROR: no method named `parse` found for opaque type
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/recursive-bound-eval.stderr b/tests/ui/impl-trait/recursive-bound-eval.stderr
new file mode 100644
index 000000000000..c7283380234d
--- /dev/null
+++ b/tests/ui/impl-trait/recursive-bound-eval.stderr
@@ -0,0 +1,42 @@
+error[E0282]: type annotations needed
+  --> $DIR/recursive-bound-eval.rs:13:28
+   |
+LL |     move || recursive_fn().parse()
+   |                            ^^^^^ cannot infer type
+
+error[E0599]: no method named `parse` found for opaque type `impl Parser<_>` in the current scope
+  --> $DIR/recursive-bound-eval.rs:13:28
+   |
+LL |     move || recursive_fn().parse()
+   |                            ^^^^^ method not found in `impl Parser<_>`
+   |
+   = help: items from traits can only be used if the trait is implemented and in scope
+help: trait `Parser` which provides `parse` is implemented but not in scope; perhaps you want to import it
+   |
+LL + use Parser;
+   |
+
+error[E0391]: cycle detected when computing type of opaque `recursive_fn::{opaque#0}`
+  --> $DIR/recursive-bound-eval.rs:11:29
+   |
+LL | pub fn recursive_fn<E>() -> impl Parser<E> {
+   |                             ^^^^^^^^^^^^^^
+   |
+note: ...which requires type-checking `recursive_fn`...
+  --> $DIR/recursive-bound-eval.rs:13:13
+   |
+LL |     move || recursive_fn().parse()
+   |             ^^^^^^^^^^^^^^
+   = note: ...which requires evaluating trait selection obligation `recursive_fn::{opaque#0}: core::marker::Unpin`...
+   = note: ...which again requires computing type of opaque `recursive_fn::{opaque#0}`, completing the cycle
+note: cycle used when computing type of `recursive_fn::{opaque#0}`
+  --> $DIR/recursive-bound-eval.rs:11:29
+   |
+LL | pub fn recursive_fn<E>() -> impl Parser<E> {
+   |                             ^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0282, E0391, E0599.
+For more information about an error, try `rustc --explain E0282`.