Add `Duration::MAX` associated constant #72436

marmeladema · 2020-05-21T19:40:19Z

(To merge after #72434)

This change introduce Duration::MAX as associated constant on the same model as u64::MAX etc.

I re-used const_checked_int_methods feature gate to constify Duration::new, it might not be the best approach but i thought this PR would help start the discussion.

rust-highfive · 2020-05-21T19:40:22Z

r? @hanna-kruppe

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lcnr · 2020-05-21T19:43:32Z

src/libcore/time.rs

-    pub fn new(secs: u64, nanos: u32) -> Duration {
-        let secs =
-            secs.checked_add((nanos / NANOS_PER_SEC) as u64).expect("overflow in Duration::new");
+    #[rustc_const_unstable(feature = "const_checked_int_methods", issue = "53718")]


Suggested change

#[rustc_const_unstable(feature = "const_checked_int_methods", issue = "53718")]

#[rustc_const_unstable(feature = "const_duration_new", issue = "53718")]

I don't think we should reuse const_checked_int_methods here.
You might have to add #![feature(const_duration_new)] to src/libcore/lib.rs so Duration::MAX can use this.

Also there should be a new tracking issue then.

rust-highfive · 2020-05-21T21:02:32Z

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##[section]Starting: Checkout rust-lang/rust@refs/pull/72436/merge to s
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+ python3 ../x.py test src/tools/expand-yaml-anchors
Ensuring the YAML anchors in the GitHub Actions config were expanded
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Diff in /checkout/src/libcore/time.rs at line 121:
     /// assert_eq!(Duration::MAX, Duration::from_new(u64::MAX, 1_000_000_000-1));
     /// ```
     #[unstable(feature = "duration_constants", issue = "57391")]
-    pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC-1);
+    pub const MAX: Duration = Duration::new(u64::MAX, NANOS_PER_SEC - 1);
     /// Creates a new `Duration` from the specified number of whole seconds and
     /// additional nanoseconds.
     /// additional nanoseconds.
Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/src/libcore/time.rs"` failed.
If you're running `tidy`, try again with `--bless`. Or, if you just want to format code, run `./x.py fmt` instead.
Build completed unsuccessfully in 0:00:41
== clock drift check ==
  local time: Thu May 21 20:04:57 UTC 2020
  network time: Thu, 21 May 2020 20:04:57 GMT
  network time: Thu, 21 May 2020 20:04:57 GMT
== end clock drift check ==

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hanna-kruppe · 2020-05-22T09:59:30Z

r? @RalfJung

RalfJung · 2020-05-23T08:26:33Z

Not sure I can just approve new APIs like that.^^ Also, there is some overlap with #72481.

Cc @rust-lang/wg-const-eval

marmeladema · 2020-05-23T10:38:23Z

Let's close this in favor of #72481 even if it does not introduce Duration::MAX quite yet.

marmeladema added 2 commits May 21, 2020 20:22

Constify Duration::new

8d908b4

Add Duration::MAX associated constant

46fc0db

rust-highfive assigned hanna-kruppe May 21, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 21, 2020

lcnr reviewed May 21, 2020

View reviewed changes

RalfJung mentioned this pull request May 21, 2020

remove pointless rustc_const_stable attribute #72434

Closed

rust-highfive assigned RalfJung and unassigned hanna-kruppe May 22, 2020

RalfJung added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 23, 2020

marmeladema closed this May 23, 2020

marmeladema deleted the duration-new-const branch May 23, 2020 10:38

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Add `Duration::MAX` associated constant #72436

Add `Duration::MAX` associated constant #72436

marmeladema commented May 21, 2020

rust-highfive commented May 21, 2020

lcnr May 21, 2020

RalfJung May 21, 2020

rust-highfive commented May 21, 2020

hanna-kruppe commented May 22, 2020

RalfJung commented May 23, 2020

marmeladema commented May 23, 2020

	#[rustc_const_unstable(feature = "const_checked_int_methods", issue = "53718")]
	#[rustc_const_unstable(feature = "const_duration_new", issue = "53718")]

Add Duration::MAX associated constant #72436

Add Duration::MAX associated constant #72436

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marmeladema commented May 21, 2020

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marmeladema commented May 23, 2020

Add `Duration::MAX` associated constant #72436

Add `Duration::MAX` associated constant #72436