Bad generic inference on very recent nightly #105037
Description
We noticed a build error in Plonky2 on the nightly build 2022-11-27. The same code was building last week, on a slightly older nightly.
Here's a minimal reproducible example (Playground):
#![feature(generic_const_exprs)] trait Table<const D: usize>: Sync { const COLUMNS: usize; } struct Table1<const D: usize>; impl<const D: usize> Table<D> for Table1<D> { const COLUMNS: usize = 123; } struct Table2<const D: usize>; impl<const D: usize> Table<D> for Table2<D> { const COLUMNS: usize = 456; } fn process_table<T: Table<D>, const D: usize>(table: T) where [(); T::COLUMNS]:, { } fn process_all_tables<const D: usize>() where [(); Table1::<D>::COLUMNS]:, [(); Table2::<D>::COLUMNS]:, { process_table(Table1::<D>); process_table(Table2::<D>); }Nightly 2022-11-27 gives this error:
error[[E0308]](https://doc.rust-lang.org/nightly/error-index.html#E0308): mismatched types --> src/lib.rs:28:19 | 28 | process_table(Table1::<D>); | ------------- ^^^^^^^^^^^ expected struct `Table2`, found struct `Table1` | | | arguments to this function are incorrect | = note: expected struct `Table2<D>` found struct `Table1<D>` It seems to be sensitive to the order of the where clauses, [(); Table1::<D>::COLUMNS]: and [(); Table2::<D>::COLUMNS]:. I.e. for a process_table call, it seems to infer that T is whichever Table appeared last in the where list.