typenum `Div` results in overflow #184

lcnr · 2025-04-23T16:38:20Z

use typenum::{consts::*, Div};
fn is_div<T: Div<U>, U>() {}
fn main() {
    is_div::<U2, U1>();
}

fails with unavoidable overflow errors in the new solver

…er-errors norm nested aliases before evaluating the parent goal see the explanation of the underlying issue in tests/ui/traits/next-solver/normalize/eager-norm-pre-normalizes-to.rs. This is also the cause of rust-lang/trait-system-refactor-initiative#184, fixing the overflow errors with the new solver. I did not add any tests based on it directly as relying on that behavior to cause recursion limit shenanigans feels fragile. Thanks `@Nadrieril` for minimizing the issue [on zulip](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/typenum.20.602.20.2F.201.60.20overflow.20error/with/513993621). r? `@compiler-errors`

Rollup merge of rust-lang#140236 - lcnr:normalizes-to-goals, r=compiler-errors norm nested aliases before evaluating the parent goal see the explanation of the underlying issue in tests/ui/traits/next-solver/normalize/eager-norm-pre-normalizes-to.rs. This is also the cause of rust-lang/trait-system-refactor-initiative#184, fixing the overflow errors with the new solver. I did not add any tests based on it directly as relying on that behavior to cause recursion limit shenanigans feels fragile. Thanks `@Nadrieril` for minimizing the issue [on zulip](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/typenum.20.602.20.2F.201.60.20overflow.20error/with/513993621). r? `@compiler-errors`

norm nested aliases before evaluating the parent goal see the explanation of the underlying issue in tests/ui/traits/next-solver/normalize/eager-norm-pre-normalizes-to.rs. This is also the cause of rust-lang/trait-system-refactor-initiative#184, fixing the overflow errors with the new solver. I did not add any tests based on it directly as relying on that behavior to cause recursion limit shenanigans feels fragile. Thanks `@Nadrieril` for minimizing the issue [on zulip](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/typenum.20.602.20.2F.201.60.20overflow.20error/with/513993621). r? `@compiler-errors`

lcnr added this to -Znext-solver=globally Apr 23, 2025

github-project-automation bot moved this to unknown in -Znext-solver=globally Apr 23, 2025

lcnr changed the title ~~typenum PartialDiv results in overflow~~ typenum Div results in overflow Apr 23, 2025

lcnr mentioned this issue Apr 24, 2025

norm nested aliases before evaluating the parent goal rust-lang/rust#140236

Merged

lcnr moved this from unknown to in progress in -Znext-solver=globally Apr 24, 2025

lcnr self-assigned this Apr 24, 2025

lcnr added the from-crater A regression found via a crater run, not part of our test suite label Apr 25, 2025

lcnr moved this from in progress to done in -Znext-solver=globally Apr 25, 2025

lcnr closed this as completed by moving to done in -Znext-solver=globally Apr 25, 2025

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