Test interaction btw async blocks and ?, return, break.

1 files changed, 67 insertions, 0 deletions

diff --git a/src/test/ui/async-await/async-block-control-flow-static-semantics.rs b/src/test/ui/async-await/async-block-control-flow-static-semantics.rs
new file mode 100644
index 00000000000..6a766ede0ed
--- /dev/null
+++ b/src/test/ui/async-await/async-block-control-flow-static-semantics.rs
@@ -0,0 +1,67 @@
+// Test that `async { .. }` blocks:
+// 1. do not allow `break` expressions.
+// 2. get targeted by `return` and not the parent function.
+// 3. get targeted by `?` and not the parent function.
+//
+// edition:2018
+// ignore-tidy-linelength
+
+#![feature(async_await)]
+
+fn main() {}
+
+use core::future::Future;
+
+fn return_targets_async_block_not_fn() -> u8 {
+    //~^ ERROR mismatched types
+    let block = async {
+        return 0u8;
+    };
+    let _: &dyn Future<Output = ()> = &block;
+    //~^ ERROR type mismatch resolving `<impl std::future::Future as std::future::Future>::Output == ()`
+}
+
+async fn return_targets_async_block_not_async_fn() -> u8 {
+    //~^ ERROR type mismatch resolving
+    let block = async {
+        return 0u8;
+    };
+    let _: &dyn Future<Output = ()> = &block;
+    //~^ ERROR type mismatch resolving `<impl std::future::Future as std::future::Future>::Output == ()`
+}
+
+fn no_break_in_async_block() {
+    async {
+        break 0u8; //~ ERROR `break` inside of a closure
+        // FIXME: This diagnostic is pretty bad.
+    };
+}
+
+fn no_break_in_async_block_even_with_outer_loop() {
+    loop {
+        async {
+            break 0u8; //~ ERROR `break` inside of a closure
+        };
+    }
+}
+
+struct MyErr;
+fn err() -> Result<u8, MyErr> { Err(MyErr) }
+
+fn rethrow_targets_async_block_not_fn() -> Result<u8, MyErr> {
+    //~^ ERROR mismatched types
+    let block = async {
+        err()?;
+        Ok(())
+    };
+    let _: &dyn Future<Output = Result<(), MyErr>> = &block;
+}
+
+fn rethrow_targets_async_block_not_async_fn() -> Result<u8, MyErr> {
+    //~^ ERROR mismatched types
+    let block = async {
+        err()?;
+        Ok(())
+    };
+    let _: &dyn Future<Output = Result<(), MyErr>> = &block;
+}