45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
//@ known-bug: #108499
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// at lower recursion limits the recursion limit is reached before the bug happens
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#![recursion_limit = "2000"]
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// this will try to calculate 3↑↑3=3^(3^3)
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type Test = <() as Op<((), ()), [[[(); 0]; 0]; 0], [[[(); 0]; 0]; 0],
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[[[[(); 0]; 0]; 0]; 0]>>::Result;
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use std::default::Default;
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fn main() {
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// force the compiler to actually evaluate `Test`
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println!("{}", Test::default());
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}
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trait Op<X, A, B, C> {
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type Result;
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}
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// this recursive function defines the hyperoperation sequence,
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// a canonical example of the type of recursion which produces the issue
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// the problem seems to be caused by having two recursive calls, the second
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// of which depending on the first
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impl<
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X: Op<(X, Y), A, [B; 0], [C; 0]>,
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Y: Op<(X, Y), A, X::Result, C>,
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A, B, C,
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> Op<(X, Y), A, [[B; 0]; 0], [C; 0]> for () {
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type Result = Y::Result;
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}
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// base cases
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impl<X, A, B> Op<X, A, B, ()> for () {
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type Result = [B; 0];
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}
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impl<X, A> Op<X, A, [(); 0], [(); 0]> for () {
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type Result = [A; 0];
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}
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impl<X, A, C> Op<X, A, [(); 0], [[C; 0]; 0]> for () {
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type Result = A;
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}
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