Auto merge of #44220 - kennytm:fix-44216-instance-plus-max-duration-should-panic, r=alexcrichton

Properly detect overflow in Instance ± Duration.

Fix #44216.
Fix #42622

The computation `Instant::now() + Duration::from_secs(u64::max_value())` now panics. The call `receiver.recv_timeout(Duration::from_secs(u64::max_value()))`, which involves such time addition, will also panic.

The reason #44216 arises is because of an unchecked cast from `u64` to `i64`, making the duration equivalent to -1 second.

Note that the current implementation is over-conservative, since e.g. (-2⁶²) + (2⁶³) is perfectly fine for an `i64`, yet this is rejected because (2⁶³) overflows the `i64`.

src/test/run-fail/issue-44216-add-instant.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// error-pattern:overflow
+
+use std::time::{Instant, Duration};
+
+fn main() {
+    let now = Instant::now();
+    let _ = now + Duration::from_secs(u64::max_value());
+}

src/test/run-fail/issue-44216-add-system-time.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// error-pattern:overflow
+
+use std::time::{Duration, SystemTime};
+
+fn main() {
+    let now = SystemTime::now();
+    let _ = now + Duration::from_secs(u64::max_value());
+}

src/test/run-fail/issue-44216-sub-instant.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// error-pattern:overflow
+
+use std::time::{Instant, Duration};
+
+fn main() {
+    let now = Instant::now();
+    let _ = now - Duration::from_secs(u64::max_value());
+}

src/test/run-fail/issue-44216-sub-system-time.rs

@@ -0,0 +1,18 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// error-pattern:overflow
+
+use std::time::{Duration, SystemTime};
+
+fn main() {
+    let now = SystemTime::now();
+    let _ = now - Duration::from_secs(u64::max_value());
+}