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It is not possible to assign a Duration to a const variable #18166

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carllerche opened this issue Oct 19, 2014 · 4 comments
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It is not possible to assign a Duration to a const variable #18166

carllerche opened this issue Oct 19, 2014 · 4 comments

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@carllerche
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The struct fields are currently not pub making it impossible to assign Duration to a const variable.

Given that Duration is essentially timespec, it seems like it might be a good idea to make the struct fields public.

cc @aturon
@ben0x539
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There's a legit timespec in liblibc by the way. I don't think the field sizes are compatible, though.

@Gankra
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Gankra commented Oct 20, 2014

Can this wait for Compile Time Function Evaluation to be implemented properly? It seems like that would be the correct solution to this problem (unless having the fields public is otherwise desirable).

1-more added a commit to 1-more/rust that referenced this issue Nov 3, 2014
@1-more
libstd’s Duration refactor
e29d5dd 
This commit changes the internal representation of Duration from

    pub struct Duraion {
        secs: i64,
        nanos: i32
    }

to

    /// An absolute amount of time, independent of time zones
    /// and calendars with tick precision. A single tick
    /// represents 100 nanoseconds.
    pub struct Duration(pub i64)

Closes rust-lang#18166,rust-lang#18416.
@1-more 1-more mentioned this issue Nov 3, 2014
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@1-more 1-more mentioned this issue Nov 11, 2014
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@steveklabnik
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This is still true today.

@steveklabnik
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Sample program:

use std::time::Duration;

const MINUTE: Duration = Duration::new(60, 0);

fn main() {}

This is basically always going to be true until const fn is stable, since things are now stable, so there's not much we can really do here, so I'm giving this a close.

lnicola pushed a commit to lnicola/rust that referenced this issue Sep 25, 2024
@bors
Auto merge of rust-lang#18166 - ChayimFriedman2:dollar-crate-root, r=…
ceb495a 
…Veykril

fix: Fix a bug in span map merge, and add explanations of how span maps are stored

Because it took me hours to figure out that contrary to common sense, the offset stored is the *end* of the node, and we search by the *start*. Which is why we need a convoluted `partition_point()` instead of a simple `binary_search()`. And this was not documented at all. Which made me make mistakes with my implementation of `SpanMap::merge()`.

The other bug fixed about span map merging is correctly keeping track of the current offset in presence of multiple sibling macro invocations. Unrelated, but because of the previous issue it took me hours to debug, so I figured out I'll put them together for posterity.

Fixes rust-lang#18163.
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libstd’s Duration refactor 1-more/rust
4 participants
@carllerche @ben0x539 @steveklabnik @Gankra