diff options
Diffstat (limited to 'compiler/rustc_middle/src/traits/solve.rs')
| -rw-r--r-- | compiler/rustc_middle/src/traits/solve.rs | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs index 27a1e64a7..048df367b 100644 --- a/compiler/rustc_middle/src/traits/solve.rs +++ b/compiler/rustc_middle/src/traits/solve.rs @@ -233,6 +233,27 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for PredefinedOpaques<'tcx> { } } +/// Why a specific goal has to be proven. +/// +/// This is necessary as we treat nested goals different depending on +/// their source. +#[derive(Copy, Clone, Debug, PartialEq, Eq)] +pub enum GoalSource { + Misc, + /// We're proving a where-bound of an impl. + /// + /// FIXME(-Znext-solver=coinductive): Explain how and why this + /// changes whether cycles are coinductive. + /// + /// This also impacts whether we erase constraints on overflow. + /// Erasing constraints is generally very useful for perf and also + /// results in better error messages by avoiding spurious errors. + /// We do not erase overflow constraints in `normalizes-to` goals unless + /// they are from an impl where-clause. This is necessary due to + /// backwards compatability, cc trait-system-refactor-initiatitive#70. + ImplWhereBound, +} + #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)] pub enum IsNormalizesToHack { Yes, |