Move /src/test to /tests

tests/ui/inference/cannot-infer-async.rs

@@ -0,0 +1,16 @@
+// edition:2018
+
+use std::io::Error;
+
+fn make_unit() -> Result<(), Error> {
+    Ok(())
+}
+
+fn main() {
+    let fut = async {
+        make_unit()?;
+
+        Ok(())
+        //~^ ERROR type annotations needed
+    };
+}