Refactor a bit & introduce Environment struct

crates/ra_hir/src/db.rs

@@ -217,7 +217,7 @@ pub trait HirDatabase: DefDatabase + AstDatabase {
     fn implements(
         &self,
         krate: Crate,
-        goal: crate::ty::Canonical<crate::ty::TraitRef>,
+        goal: crate::ty::Canonical<crate::ty::InEnvironment<crate::ty::TraitRef>>,
     ) -> Option<crate::ty::traits::Solution>;
 
     #[salsa::invoke(crate::ty::traits::normalize_query)]

crates/ra_hir/src/ty.rs

@@ -26,7 +26,7 @@ pub(crate) use lower::{
     callable_item_sig, generic_defaults_query, generic_predicates_query, type_for_def,
     type_for_field, TypableDef,
 };
-pub(crate) use traits::ProjectionPredicate;
+pub(crate) use traits::{Environment, InEnvironment, ProjectionPredicate};
 
 /// A type constructor or type name: this might be something like the primitive
 /// type `bool`, a struct like `Vec`, or things like function pointers or

crates/ra_hir/src/ty/infer.rs

@@ -29,7 +29,8 @@ use test_utils::tested_by;
 use super::{
     autoderef, method_resolution, op, primitive,
     traits::{Guidance, Obligation, ProjectionPredicate, Solution},
-    ApplicationTy, CallableDef, ProjectionTy, Substs, TraitRef, Ty, TypableDef, TypeCtor,
+    ApplicationTy, CallableDef, InEnvironment, ProjectionTy, Substs, TraitRef, Ty, TypableDef,
+    TypeCtor,
 };
 use crate::{
     adt::VariantDef,
@@ -330,7 +331,9 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         for obligation in obligations {
             match &obligation {
                 Obligation::Trait(tr) => {
-                    let canonicalized = self.canonicalizer().canonicalize_trait_ref(tr.clone());
+                    let env = Arc::new(super::Environment); // FIXME add environment
+                    let in_env = InEnvironment::new(env, tr.clone());
+                    let canonicalized = self.canonicalizer().canonicalize_trait_ref(in_env);
                     let solution = self
                         .db
                         .implements(self.resolver.krate().unwrap(), canonicalized.value.clone());

crates/ra_hir/src/ty/infer/unify.rs

@@ -2,7 +2,9 @@
 
 use super::InferenceContext;
 use crate::db::HirDatabase;
-use crate::ty::{Canonical, InferTy, ProjectionPredicate, ProjectionTy, TraitRef, Ty};
+use crate::ty::{
+    Canonical, InEnvironment, InferTy, ProjectionPredicate, ProjectionTy, TraitRef, Ty,
+};
 
 impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     pub(super) fn canonicalizer<'b>(&'b mut self) -> Canonicalizer<'a, 'b, D>
@@ -105,14 +107,24 @@ where
         ProjectionPredicate { ty, projection_ty }
     }
 
+    // FIXME: add some point, we need to introduce a `Fold` trait that abstracts
+    // over all the things that can be canonicalized (like Chalk and rustc have)
+
     pub fn canonicalize_ty(mut self, ty: Ty) -> Canonicalized<Ty> {
         let result = self.do_canonicalize_ty(ty);
         self.into_canonicalized(result)
     }
 
-    pub fn canonicalize_trait_ref(mut self, trait_ref: TraitRef) -> Canonicalized<TraitRef> {
-        let result = self.do_canonicalize_trait_ref(trait_ref);
-        self.into_canonicalized(result)
+    pub fn canonicalize_trait_ref(
+        mut self,
+        trait_ref_in_env: InEnvironment<TraitRef>,
+    ) -> Canonicalized<InEnvironment<TraitRef>> {
+        let result = self.do_canonicalize_trait_ref(trait_ref_in_env.value);
+        // FIXME canonicalize env
+        self.into_canonicalized(InEnvironment {
+            value: result,
+            environment: trait_ref_in_env.environment,
+        })
     }
 
     pub fn canonicalize_projection(

crates/ra_hir/src/ty/method_resolution.rs

@@ -7,7 +7,7 @@ use std::sync::Arc;
 use arrayvec::ArrayVec;
 use rustc_hash::FxHashMap;
 
-use super::{autoderef, Canonical, TraitRef};
+use super::{autoderef, Canonical, Environment, InEnvironment, TraitRef};
 use crate::{
     generics::HasGenericParams,
     impl_block::{ImplBlock, ImplId, ImplItem},
@@ -209,7 +209,8 @@ fn iterate_trait_method_candidates<T>(
                 let data = m.data(db);
                 if name.map_or(true, |name| data.name() == name) && data.has_self_param() {
                     if !known_implemented {
-                        let trait_ref = canonical_trait_ref(db, t, ty.clone());
+                        let env = Arc::new(super::Environment); // FIXME add environment
+                        let trait_ref = canonical_trait_ref(db, env, t, ty.clone());
                         if db.implements(krate, trait_ref).is_none() {
                             continue 'traits;
                         }
@@ -279,9 +280,10 @@ impl Ty {
 /// for all other parameters, to query Chalk with it.
 fn canonical_trait_ref(
     db: &impl HirDatabase,
+    env: Arc<Environment>,
     trait_: Trait,
     self_ty: Canonical<Ty>,
-) -> Canonical<TraitRef> {
+) -> Canonical<InEnvironment<TraitRef>> {
     let mut substs = Vec::new();
     let generics = trait_.generic_params(db);
     let num_vars = self_ty.num_vars;
@@ -296,6 +298,6 @@ fn canonical_trait_ref(
     );
     Canonical {
         num_vars: substs.len() - 1 + self_ty.num_vars,
-        value: TraitRef { trait_, substs: substs.into() },
+        value: InEnvironment::new(env, TraitRef { trait_, substs: substs.into() }),
     }
 }

crates/ra_hir/src/ty/traits.rs

@@ -67,6 +67,27 @@ fn solve(
     solution
 }
 
+/// A set of clauses that we assume to be true. E.g. if we are inside this function:
+/// ```rust
+/// fn foo<T: Default>(t: T) {}
+/// ```
+/// we assume that `T: Default`.
+#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct Environment;
+
+/// Something (usually a goal), along with an environment.
+#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct InEnvironment<T> {
+    pub environment: Arc<Environment>,
+    pub value: T,
+}
+
+impl<T> InEnvironment<T> {
+    pub fn new(environment: Arc<Environment>, value: T) -> InEnvironment<T> {
+        InEnvironment { environment, value }
+    }
+}
+
 /// Something that needs to be proven (by Chalk) during type checking, e.g. that
 /// a certain type implements a certain trait. Proving the Obligation might
 /// result in additional information about inference variables.
@@ -97,16 +118,10 @@ pub struct ProjectionPredicate {
 pub(crate) fn implements_query(
     db: &impl HirDatabase,
     krate: Crate,
-    trait_ref: Canonical<TraitRef>,
+    trait_ref: Canonical<InEnvironment<TraitRef>>,
 ) -> Option<Solution> {
     let _p = profile("implements_query");
-    let goal: chalk_ir::Goal = trait_ref.value.to_chalk(db).cast();
-    debug!("goal: {:?}", goal);
-    let env = chalk_ir::Environment::new();
-    let in_env = chalk_ir::InEnvironment::new(&env, goal);
-    let parameter = chalk_ir::ParameterKind::Ty(chalk_ir::UniverseIndex::ROOT);
-    let canonical =
-        chalk_ir::Canonical { value: in_env, binders: vec![parameter; trait_ref.num_vars] };
+    let canonical = trait_ref.to_chalk(db).cast();
     // We currently don't deal with universes (I think / hope they're not yet
     // relevant for our use cases?)
     let u_canonical = chalk_ir::UCanonical { canonical, universes: 1 };

crates/ra_hir/src/ty/traits/chalk.rs

@@ -12,7 +12,7 @@ use chalk_rust_ir::{AssociatedTyDatum, ImplDatum, StructDatum, TraitDatum};
 use ra_db::salsa::{InternId, InternKey};
 use test_utils::tested_by;
 
-use super::ChalkContext;
+use super::{Canonical, ChalkContext};
 use crate::{
     db::HirDatabase,
     generics::GenericDef,
@@ -218,6 +218,60 @@ impl ToChalk for ProjectionTy {
     }
 }
 
+impl<T> ToChalk for Canonical<T>
+where
+    T: ToChalk,
+{
+    type Chalk = chalk_ir::Canonical<T::Chalk>;
+
+    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
+        let parameter = chalk_ir::ParameterKind::Ty(chalk_ir::UniverseIndex::ROOT);
+        let value = self.value.to_chalk(db);
+        let canonical = chalk_ir::Canonical { value, binders: vec![parameter; self.num_vars] };
+        canonical
+    }
+
+    fn from_chalk(db: &impl HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
+        Canonical { num_vars: canonical.binders.len(), value: from_chalk(db, canonical.value) }
+    }
+}
+
+impl ToChalk for Arc<super::Environment> {
+    type Chalk = Arc<chalk_ir::Environment>;
+
+    fn to_chalk(self, _db: &impl HirDatabase) -> Arc<chalk_ir::Environment> {
+        chalk_ir::Environment::new()
+    }
+
+    fn from_chalk(
+        _db: &impl HirDatabase,
+        _env: Arc<chalk_ir::Environment>,
+    ) -> Arc<super::Environment> {
+        Arc::new(super::Environment)
+    }
+}
+
+impl<T: ToChalk> ToChalk for super::InEnvironment<T> {
+    type Chalk = chalk_ir::InEnvironment<T::Chalk>;
+
+    fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::InEnvironment<T::Chalk> {
+        chalk_ir::InEnvironment {
+            environment: self.environment.to_chalk(db),
+            goal: self.value.to_chalk(db),
+        }
+    }
+
+    fn from_chalk(
+        db: &impl HirDatabase,
+        in_env: chalk_ir::InEnvironment<T::Chalk>,
+    ) -> super::InEnvironment<T> {
+        super::InEnvironment {
+            environment: from_chalk(db, in_env.environment),
+            value: from_chalk(db, in_env.goal),
+        }
+    }
+}
+
 fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T> {
     chalk_ir::Binders {
         value,