From 19e51aaef7cf2f7a9e0e72168caf73a94a1cbfb1 Mon Sep 17 00:00:00 2001
From: marmeladema <xademax@gmail.com>
Date: Tue, 20 Apr 2021 23:33:13 +0100
Subject: [PATCH] Add test for issue #79636

---
 .../generic-associated-types/issue-79636-1.rs | 24 +++++++++++++++++++
 .../issue-79636-1.stderr                      | 19 +++++++++++++++
 .../generic-associated-types/issue-79636-2.rs | 18 ++++++++++++++
 .../issue-79636-2.stderr                      | 19 +++++++++++++++
 4 files changed, 80 insertions(+)
 create mode 100644 src/test/ui/generic-associated-types/issue-79636-1.rs
 create mode 100644 src/test/ui/generic-associated-types/issue-79636-1.stderr
 create mode 100644 src/test/ui/generic-associated-types/issue-79636-2.rs
 create mode 100644 src/test/ui/generic-associated-types/issue-79636-2.stderr

diff --git a/src/test/ui/generic-associated-types/issue-79636-1.rs b/src/test/ui/generic-associated-types/issue-79636-1.rs
new file mode 100644
index 00000000000..17f9387e292
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-79636-1.rs
@@ -0,0 +1,24 @@
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+trait Monad {
+    type Unwrapped;
+    type Wrapped<B>;
+         //~^ ERROR: missing generics for associated type `Monad::Wrapped`
+
+    fn bind<B, F>(self, f: F) -> Self::Wrapped<B> {
+        todo!()
+    }
+}
+
+fn join<MOuter, MInner, A>(outer: MOuter) -> MOuter::Wrapped<A>
+where
+    MOuter: Monad<Unwrapped = MInner>,
+    MInner: Monad<Unwrapped = A, Wrapped = MOuter::Wrapped<A>>,
+{
+    outer.bind(|inner| inner)
+}
+
+fn main() {
+    assert_eq!(join(Some(Some(true))), Some(true));
+}
diff --git a/src/test/ui/generic-associated-types/issue-79636-1.stderr b/src/test/ui/generic-associated-types/issue-79636-1.stderr
new file mode 100644
index 00000000000..58eeb43f70d
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-79636-1.stderr
@@ -0,0 +1,19 @@
+error[E0107]: missing generics for associated type `Monad::Wrapped`
+  --> $DIR/issue-79636-1.rs:6:10
+   |
+LL |     type Wrapped<B>;
+   |          ^^^^^^^ expected 1 type argument
+   |
+note: associated type defined here, with 1 type parameter: `B`
+  --> $DIR/issue-79636-1.rs:6:10
+   |
+LL |     type Wrapped<B>;
+   |          ^^^^^^^ -
+help: use angle brackets to add missing type argument
+   |
+LL |     type Wrapped<B><B>;
+   |                 ^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.
diff --git a/src/test/ui/generic-associated-types/issue-79636-2.rs b/src/test/ui/generic-associated-types/issue-79636-2.rs
new file mode 100644
index 00000000000..5a654219375
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-79636-2.rs
@@ -0,0 +1,18 @@
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+
+trait SomeTrait {
+    type Wrapped<A>: SomeTrait;
+         //~^ ERROR: missing generics for associated type `SomeTrait::Wrapped`
+
+    fn f() -> ();
+}
+
+fn program<W>() -> ()
+where
+    W: SomeTrait<Wrapped = W>,
+{
+    return W::f();
+}
+
+fn main() {}
diff --git a/src/test/ui/generic-associated-types/issue-79636-2.stderr b/src/test/ui/generic-associated-types/issue-79636-2.stderr
new file mode 100644
index 00000000000..d5e3c56ebb9
--- /dev/null
+++ b/src/test/ui/generic-associated-types/issue-79636-2.stderr
@@ -0,0 +1,19 @@
+error[E0107]: missing generics for associated type `SomeTrait::Wrapped`
+  --> $DIR/issue-79636-2.rs:5:10
+   |
+LL |     type Wrapped<A>: SomeTrait;
+   |          ^^^^^^^ expected 1 type argument
+   |
+note: associated type defined here, with 1 type parameter: `A`
+  --> $DIR/issue-79636-2.rs:5:10
+   |
+LL |     type Wrapped<A>: SomeTrait;
+   |          ^^^^^^^ -
+help: use angle brackets to add missing type argument
+   |
+LL |     type Wrapped<A><A>: SomeTrait;
+   |                 ^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.