Reorganize hir_ty modules

Chalk isn't really a 'traits' thing anymore, so it doesn't make sense to
have all the Chalk-related stuff in submodules of `traits`.

1 files changed, 125 insertions, 0 deletions

diff --git a/crates/hir_ty/src/mapping.rs b/crates/hir_ty/src/mapping.rs
new file mode 100644
index 000000000..4d3c41b2c
--- /dev/null
+++ b/crates/hir_ty/src/mapping.rs
@@ -0,0 +1,125 @@
+//! This module contains the implementations of the `ToChalk` trait, which
+//! handles conversion between our data types and their corresponding types in
+//! Chalk (in both directions); plus some helper functions for more specialized
+//! conversions.
+
+use chalk_ir::{DebruijnIndex, cast::Cast, fold::Shift};
+use chalk_solve::rust_ir;
+
+use base_db::salsa::InternKey;
+use hir_def::{GenericDefId, TypeAliasId};
+
+use crate::{AliasEq, AliasTy, CallableDefId, FnDefId, Interner, ProjectionTyExt, QuantifiedWhereClause, Substitution, Ty, WhereClause, chalk_db::{self, ToChalk}, db::HirDatabase};
+
+impl ToChalk for hir_def::TraitId {
+    type Chalk = chalk_db::TraitId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::TraitId {
+        chalk_ir::TraitId(self.as_intern_id())
+    }
+
+    fn from_chalk(_db: &dyn HirDatabase, trait_id: chalk_db::TraitId) -> hir_def::TraitId {
+        InternKey::from_intern_id(trait_id.0)
+    }
+}
+
+impl ToChalk for hir_def::ImplId {
+    type Chalk = chalk_db::ImplId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::ImplId {
+        chalk_ir::ImplId(self.as_intern_id())
+    }
+
+    fn from_chalk(_db: &dyn HirDatabase, impl_id: chalk_db::ImplId) -> hir_def::ImplId {
+        InternKey::from_intern_id(impl_id.0)
+    }
+}
+
+impl ToChalk for CallableDefId {
+    type Chalk = FnDefId;
+
+    fn to_chalk(self, db: &dyn HirDatabase) -> FnDefId {
+        db.intern_callable_def(self).into()
+    }
+
+    fn from_chalk(db: &dyn HirDatabase, fn_def_id: FnDefId) -> CallableDefId {
+        db.lookup_intern_callable_def(fn_def_id.into())
+    }
+}
+
+pub(crate) struct TypeAliasAsValue(pub(crate) TypeAliasId);
+
+impl ToChalk for TypeAliasAsValue {
+    type Chalk = chalk_db::AssociatedTyValueId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::AssociatedTyValueId {
+        rust_ir::AssociatedTyValueId(self.0.as_intern_id())
+    }
+
+    fn from_chalk(
+        _db: &dyn HirDatabase,
+        assoc_ty_value_id: chalk_db::AssociatedTyValueId,
+    ) -> TypeAliasAsValue {
+        TypeAliasAsValue(TypeAliasId::from_intern_id(assoc_ty_value_id.0))
+    }
+}
+
+pub(super) fn convert_where_clauses(
+    db: &dyn HirDatabase,
+    def: GenericDefId,
+    substs: &Substitution,
+) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
+    let generic_predicates = db.generic_predicates(def);
+    let mut result = Vec::with_capacity(generic_predicates.len());
+    for pred in generic_predicates.iter() {
+        result.push(pred.clone().substitute(&Interner, substs));
+    }
+    result
+}
+
+pub(super) fn generic_predicate_to_inline_bound(
+    db: &dyn HirDatabase,
+    pred: &QuantifiedWhereClause,
+    self_ty: &Ty,
+) -> Option<chalk_ir::Binders<rust_ir::InlineBound<Interner>>> {
+    // An InlineBound is like a GenericPredicate, except the self type is left out.
+    // We don't have a special type for this, but Chalk does.
+    let self_ty_shifted_in = self_ty.clone().shifted_in_from(&Interner, DebruijnIndex::ONE);
+    let (pred, binders) = pred.as_ref().into_value_and_skipped_binders();
+    match pred {
+        WhereClause::Implemented(trait_ref) => {
+            if trait_ref.self_type_parameter(&Interner) != self_ty_shifted_in {
+                // we can only convert predicates back to type bounds if they
+                // have the expected self type
+                return None;
+            }
+            let args_no_self = trait_ref.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let trait_bound = rust_ir::TraitBound { trait_id: trait_ref.trait_id, args_no_self };
+            Some(chalk_ir::Binders::new(binders, rust_ir::InlineBound::TraitBound(trait_bound)))
+        }
+        WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
+            if projection_ty.self_type_parameter(&Interner) != self_ty_shifted_in {
+                return None;
+            }
+            let trait_ = projection_ty.trait_(db);
+            let args_no_self = projection_ty.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let alias_eq_bound = rust_ir::AliasEqBound {
+                value: ty.clone(),
+                trait_bound: rust_ir::TraitBound { trait_id: trait_.to_chalk(db), args_no_self },
+                associated_ty_id: projection_ty.associated_ty_id,
+                parameters: Vec::new(), // FIXME we don't support generic associated types yet
+            };
+            Some(chalk_ir::Binders::new(
+                binders,
+                rust_ir::InlineBound::AliasEqBound(alias_eq_bound),
+            ))
+        }
+        _ => None,
+    }
+}