From 29dffe517609c9ac7416c7a32febf7905010083a Mon Sep 17 00:00:00 2001
From: Santiago Pastorino <spastorino@gmail.com>
Date: Fri, 20 Aug 2021 22:50:13 -0300
Subject: [PATCH] Test that incomplete inference for TAITs fail

---
 .../incomplete-inference.rs                   | 15 +++++++++++++
 .../incomplete-inference.stderr               | 21 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 src/test/ui/type-alias-impl-trait/incomplete-inference.rs
 create mode 100644 src/test/ui/type-alias-impl-trait/incomplete-inference.stderr

diff --git a/src/test/ui/type-alias-impl-trait/incomplete-inference.rs b/src/test/ui/type-alias-impl-trait/incomplete-inference.rs
new file mode 100644
index 00000000000..955d1288a45
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/incomplete-inference.rs
@@ -0,0 +1,15 @@
+#![feature(type_alias_impl_trait)]
+
+type Foo = impl Sized;
+
+fn bar() -> Foo {
+    None
+    //~^ ERROR: type annotations needed [E0282]
+}
+
+fn baz() -> Foo {
+    //~^ ERROR: concrete type differs from previous defining opaque type use
+    Some(())
+}
+
+fn main() {}
diff --git a/src/test/ui/type-alias-impl-trait/incomplete-inference.stderr b/src/test/ui/type-alias-impl-trait/incomplete-inference.stderr
new file mode 100644
index 00000000000..53cdf9e5b38
--- /dev/null
+++ b/src/test/ui/type-alias-impl-trait/incomplete-inference.stderr
@@ -0,0 +1,21 @@
+error[E0282]: type annotations needed
+  --> $DIR/incomplete-inference.rs:6:5
+   |
+LL |     None
+   |     ^^^^ cannot infer type for type parameter `T` declared on the enum `Option`
+
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/incomplete-inference.rs:10:1
+   |
+LL | fn baz() -> Foo {
+   | ^^^^^^^^^^^^^^^ expected `[type error]`, got `Option<()>`
+   |
+note: previous use here
+  --> $DIR/incomplete-inference.rs:5:1
+   |
+LL | fn bar() -> Foo {
+   | ^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0282`.
-- 
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