Centril

Error Index

E0001

This error occurs when #[derive(Arbitrary)] is used on a type which has any lifetime parameters. For example:

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Given the following type definitions:

struct Foo(usize);

struct Wrapping<T>(T);

struct Product<A, B>(A, B);

trait Trait { type Assoc; }

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    // while P { B_1 } else { B_2 } */
    // ==>
    /*
    if P {
        B_1;

        while P {
            B_1
        }

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Unnamed structs

Nominal type equivalence

Let ≡n be the equivalence class of nominally equivalent types. A ≡n B denotes that A and B are nominally the same type.

{ foo: T, bar: U } ≡n { bar: U, foo: T } // Order does not matter.

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Keyword policy

Upsides of proper keywords (with no availability on old editions)

• Avoid monotonically increasing tech debt
  • In particular, if contextual keywords accumulate over time, their grammatical interactions are going to get continually trickier
• Forward-compatible with introducing contextual keywords on older editions
• Forward-compatible with future uses that can’t be contextual
  • In case we decide 1.5 year hence that we want to do something new with the keyword.
• Arguably can give better error messages
• Cleaner

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Notes on adding Constraint Kinds to Rust

Background: Constraint Kinds

a trait can be thought of as a type operator generating a "constraint" - what in Rust would usually be called a bound. For example:

// Declares a new item `Foo` with kind `type -> constraint`
trait Foo { }

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//******************************************************************************
// "const_trait_system"
//******************************************************************************

/*
Dependency DAG of proposal:

[A, B] -> []
[C] -> [B] and/or [A]  -- NOTE: C is moot without B or A.
[D, E] -> [B]

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fn main() {
    use std::mem::{size_of, size_of_val};

    let susize = size_of::<usize>();

    // usize is size_t.

    // "hello" is in static memory, x is on the stack and like: (char*, usize).
    // &'static str is a fat pointer.
    // It is not null terminated.

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#![feature(core)]
#![feature(std_misc)]

use std::thread::{Thread, JoinGuard};

fn callback(v: usize) -> usize { v * 2 }

struct S {
    cb: Box<Fn(usize) -> usize + Send>,
}

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Keybase proof

I hereby claim:

• I am Centril on github.
• I am centril (https://keybase.io/centril) on keybase.
• I have a public key whose fingerprint is 17DC 71EF 7AD7 4032 4B5D 112E 818B 6F39 DE23 A081

To claim this, I am signing this object: