[perf] Compute hard errors without diagnostics in impl_intersection_has_impossible_obligation First compute hard errors without diagnostics, then ambiguities with diagnostics since we need to know if any of them overflowed.
[perf] Compute hard errors without diagnostics in impl_intersection_has_impossible_obligation First compute hard errors without diagnostics, then ambiguities with diagnostics since we need to know if any of them overflowed.