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add test for 62220 #70539

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Mar 29, 2020
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add test for 62220 #70539

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22 changes: 22 additions & 0 deletions src/test/ui/const-generics/issues/issue-62220.rs
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// build-pass
#![allow(incomplete_features)]

#![feature(const_generics)]
pub struct Vector<T, const N: usize>([T; N]);

pub type TruncatedVector<T, const N: usize> = Vector<T, { N - 1 }>;
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@eddyb @varkor Shouldn't error: constant expression depends on a generic parameter happen here or is this cause we're not applying WF for type aliases... but then why won't it happen for the usage below?

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We're not doing const WF at all except for array types, today.
#70107 aims to fix that.

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Ah; forgot that hadn't landed yet. Let's merge this PR like this then once the other comment has been addressed and we can make adjustments later in the other.


impl<T, const N: usize> Vector<T, { N }> {
/// Drop the last component and return the vector with one fewer dimension.
pub fn trunc(self) -> (TruncatedVector<T, { N }>, T) {
unimplemented!()
}
}

fn vec4<T>(a: T, b: T, c: T, d: T) -> Vector<T, 4> {
Vector([a, b, c, d])
}

fn main() {
let (_xyz, _w): (TruncatedVector<u32, 4>, u32) = vec4(0u32, 1, 2, 3).trunc();
}