Add test for try operator on Result

src/test/ui/consts/try-operator.rs

@@ -0,0 +1,16 @@
+// run-pass
+
+#![feature(try_trait_v2)]
+#![feature(const_trait_impl)]
+#![feature(const_try)]
+#![feature(const_convert)]
+
+fn main() {
+    const fn foo() -> Result<bool, ()> {
+        Err(())?;
+        Ok(true)
+    }
+
+    const FOO: Result<bool, ()> = foo();
+    assert_eq!(Err(()), FOO);
+}