Add out-of-{async,generators} tests

Author: WaffleLapkin

tests/ui/explicit-tail-calls/out-of-async.rs

@@ -0,0 +1,20 @@
+// edition: 2021
+#![feature(explicit_tail_calls)]
+
+async fn a() {
+    become b();
+    //~^ error: mismatched function ABIs
+    //~| error: mismatched signatures
+}
+
+fn b() {}
+
+fn block() -> impl std::future::Future<Output = ()> {
+    async {
+        become b();
+        //~^ error: mismatched function ABIs
+        //~| error: mismatched signatures
+    }
+}
+
+fn main() {}

tests/ui/explicit-tail-calls/out-of-async.stderr

@@ -0,0 +1,40 @@
+error: mismatched function ABIs
+  --> $DIR/out-of-async.rs:5:5
+   |
+LL |     become b();
+   |     ^^^^^^^^^^
+   |
+   = note: `become` requires caller and callee to have the same ABI
+   = note: caller ABI is `"rust-call"`, while callee ABI is `"Rust"`
+
+error: mismatched signatures
+  --> $DIR/out-of-async.rs:5:5
+   |
+LL |     become b();
+   |     ^^^^^^^^^^
+   |
+   = note: `become` requires caller and callee to have matching signatures
+   = note: caller signature: `extern "rust-call" fn(ResumeTy)`
+   = note: callee signature: `fn()`
+
+error: mismatched function ABIs
+  --> $DIR/out-of-async.rs:14:9
+   |
+LL |         become b();
+   |         ^^^^^^^^^^
+   |
+   = note: `become` requires caller and callee to have the same ABI
+   = note: caller ABI is `"rust-call"`, while callee ABI is `"Rust"`
+
+error: mismatched signatures
+  --> $DIR/out-of-async.rs:14:9
+   |
+LL |         become b();
+   |         ^^^^^^^^^^
+   |
+   = note: `become` requires caller and callee to have matching signatures
+   = note: caller signature: `extern "rust-call" fn(ResumeTy)`
+   = note: callee signature: `fn()`
+
+error: aborting due to 4 previous errors
+

tests/ui/explicit-tail-calls/out-of-generators.rs

@@ -0,0 +1,11 @@
+#![feature(explicit_tail_calls)]
+#![feature(generators)]
+
+fn main() {
+    let _generator = || {
+        yield 1;
+        become f() //~ error: mismatched function ABIs
+    };
+}
+
+fn f() {}

tests/ui/explicit-tail-calls/out-of-generators.stderr

@@ -0,0 +1,11 @@
+error: mismatched function ABIs
+  --> $DIR/out-of-generators.rs:7:9
+   |
+LL |         become f()
+   |         ^^^^^^^^^^
+   |
+   = note: `become` requires caller and callee to have the same ABI
+   = note: caller ABI is `"rust-call"`, while callee ABI is `"Rust"`
+
+error: aborting due to previous error
+