[rust-lang/rust] [ICE]: `type variables should not be hashed`

**ROOT CAUSE** The ICE occurs because the compiler attempts to hash type variables (e.g., `?0t`), which is not allowed. Type variables are placeholders for unknown types and should not be hashed during compilation. **CODE FIX** Modify the `TyKind` implementation to skip hashing type variables. Specifically, update the `Hash` and `HashStable` traits for `TyKind` to handle the `Infer` variant (which represents type variables) by returning early without hashing. ```rust // In rustc_type_ir/src/ty_kind.rs impl Hash for TyKind { fn hash(&self, hcx: &mut H) { match self { // ... existing cases ... TyKind::Infer => { // Do not hash type variables. return; } // ... other cases ... } } } impl HashStable for TyKind { fn hash_stable(&self, hcx: &mut S) { match self { // ... existing cases ... TyKind::Infer => { // Do not hash type variables. return; } // ... other cases ... } } } ``` This change ensures type variables are excluded from the hash computation, preventing the ICE.