mirror of https://github.com/rust-lang/rust.git
110 lines
2.1 KiB
Rust
110 lines
2.1 KiB
Rust
//@ known-bug: #23707
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//@ compile-flags: -Copt-level=0 --edition=2021
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//@ only-x86_64
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#![recursion_limit="2048"]
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use std::marker::PhantomData;
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use std::fmt;
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use std::fmt::Debug;
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pub struct Z( () );
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pub struct S<T> (PhantomData<T>);
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pub trait Nat {
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fn sing() -> Self;
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fn get(&self) -> usize;
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}
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impl Nat for Z {
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fn sing() -> Z { Z( () ) }
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#[inline(always)]
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fn get(&self) -> usize {
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0
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}
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}
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impl<T : Nat> Nat for S<T> {
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fn sing() -> S<T> { S::<T>( PhantomData::<T> ) }
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#[inline(always)]
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fn get(&self) -> usize {
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let prd : T = Nat::sing();
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1 + prd.get()
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}
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}
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pub type N0 = Z;
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pub type N1 = S<N0>;
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pub type N2 = S<N1>;
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pub type N3 = S<N2>;
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pub type N4 = S<N3>;
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pub type N5 = S<N4>;
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pub struct Node<D : Nat>(usize,PhantomData<D>);
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impl<D:Nat> Node<D> {
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pub fn push(&self, c : usize) -> Node<S<D>> {
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let Node(i,_) = *self;
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Node(10*i+c, PhantomData::<S<D>>)
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}
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}
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impl<D:Nat> Node<S<D>> {
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pub fn pop(&self) -> (Node<D>,usize) {
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let Node(i,_) = *self;
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(Node(i/10, PhantomData::<D>), i-10*(i/10))
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}
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}
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impl<D:Nat> Debug for Node<D> {
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fn fmt(&self, f : &mut fmt::Formatter) -> fmt::Result {
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let s : D = Nat::sing();
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write!(f, "Node<{}>: i= {}",
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s.get(), self.0)
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}
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}
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pub trait Step {
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fn step(&self, usize) -> Self;
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}
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impl Step for Node<N0> {
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#[inline(always)]
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fn step(&self, n : usize) -> Node<N0> {
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println!("base case");
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Node(n,PhantomData::<N0>)
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}
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}
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impl<D:Nat> Step for Node<S<D>>
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where Node<D> : Step {
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#[inline(always)]
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fn step(&self, n : usize) -> Node<S<D>> {
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println!("rec");
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let (par,c) = self.pop();
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let cnew = c+n;
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par.step(c).push(cnew)
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}
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}
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fn tst<D:Nat>(ref p : &Node<D>, c : usize) -> usize
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where Node<D> : Step {
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let Node(i,_) = p.step(c);
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i
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}
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fn main() {
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let nd : Node<N3> = Node(555,PhantomData::<N3>);
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// overflow...core::marker::Size
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let Node(g,_) = tst(nd,1);
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// ok
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//let Node(g,_) = nd.step(1);
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println!("{:?}", g);
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}
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