Merge #8327

8327: Move `Ty` creation methods out of `Ty` (Chalk move preparation) r=flodiebold a=flodiebold

When we'll move to using `chalk_ir::Ty` (#8313), we won't be able to have our own inherent methods on `Ty` anymore, so we need to move the helpers elsewhere.
This adds a `TyBuilder` that allows easily constructing `Ty` and related types (`TraitRef`, `ProjectionTy`, `Substitution`). It also replaces `SubstsBuilder`. `TyBuilder` can construct different things based on its type parameter; e.g. if it has an `AdtId`, we're constructing an ADT type, but if it has a `TraitId`, we're constructing a `TraitRef`. The common thing for all of them is that we need to build a `Substitution`, so the API stays the same for all of them except at the beginning and end.

We also use `TyBuilder` to house various one-shot methods for constructing types, e.g. `TyBuilder::unit()`.

Co-authored-by: Florian Diebold <[email protected]>

Author: bors[bot]

crates/hir/src/display.rs

@@ -13,7 +13,7 @@ use syntax::ast::{self, NameOwner};
 
 use crate::{
     Adt, Const, ConstParam, Enum, Field, Function, GenericParam, HasVisibility, LifetimeParam,
-    Module, Static, Struct, Substitution, Trait, Type, TypeAlias, TypeParam, Union, Variant,
+    Module, Static, Struct, Trait, TyBuilder, Type, TypeAlias, TypeParam, Union, Variant,
 };
 
 impl HirDisplay for Function {
@@ -234,7 +234,7 @@ impl HirDisplay for TypeParam {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         write!(f, "{}", self.name(f.db))?;
         let bounds = f.db.generic_predicates_for_param(self.id);
-        let substs = Substitution::type_params(f.db, self.id.parent);
+        let substs = TyBuilder::type_params_subst(f.db, self.id.parent);
         let predicates = bounds.iter().cloned().map(|b| b.subst(&substs)).collect::<Vec<_>>();
         if !(predicates.is_empty() || f.omit_verbose_types()) {
             write_bounds_like_dyn_trait_with_prefix(":", &predicates, f)?;

crates/hir/src/lib.rs

@@ -55,11 +55,10 @@ use hir_ty::{
     autoderef, could_unify,
     method_resolution::{self, TyFingerprint},
     primitive::UintTy,
-    to_assoc_type_id,
     traits::{FnTrait, Solution, SolutionVariables},
     AliasEq, AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, CanonicalVarKinds, Cast,
-    DebruijnIndex, InEnvironment, Interner, ProjectionTy, QuantifiedWhereClause, Scalar,
-    Substitution, TraitEnvironment, Ty, TyDefId, TyKind, TyVariableKind, WhereClause,
+    DebruijnIndex, InEnvironment, Interner, QuantifiedWhereClause, Scalar, Substitution,
+    TraitEnvironment, Ty, TyBuilder, TyDefId, TyKind, TyVariableKind, WhereClause,
 };
 use itertools::Itertools;
 use rustc_hash::FxHashSet;
@@ -515,7 +514,7 @@ impl Field {
             VariantDef::Union(it) => it.id.into(),
             VariantDef::Variant(it) => it.parent.id.into(),
         };
-        let substs = Substitution::type_params(db, generic_def_id);
+        let substs = TyBuilder::type_params_subst(db, generic_def_id);
         let ty = db.field_types(var_id)[self.id].clone().subst(&substs);
         Type::new(db, self.parent.module(db).id.krate(), var_id, ty)
     }
@@ -1129,7 +1128,7 @@ pub struct BuiltinType {
 impl BuiltinType {
     pub fn ty(self, db: &dyn HirDatabase, module: Module) -> Type {
         let resolver = module.id.resolver(db.upcast());
-        Type::new_with_resolver(db, &resolver, Ty::builtin(self.inner))
+        Type::new_with_resolver(db, &resolver, TyBuilder::builtin(self.inner))
             .expect("crate not present in resolver")
     }
 
@@ -1502,7 +1501,7 @@ impl TypeParam {
         let resolver = self.id.parent.resolver(db.upcast());
         let krate = self.id.parent.module(db.upcast()).krate();
         let ty = params.get(local_idx)?.clone();
-        let subst = Substitution::type_params(db, self.id.parent);
+        let subst = TyBuilder::type_params_subst(db, self.id.parent);
         let ty = ty.subst(&subst.prefix(local_idx));
         Some(Type::new_with_resolver_inner(db, krate, &resolver, ty))
     }
@@ -1703,10 +1702,9 @@ impl Type {
     fn from_def(
         db: &dyn HirDatabase,
         krate: CrateId,
-        def: impl HasResolver + Into<TyDefId> + Into<GenericDefId>,
+        def: impl HasResolver + Into<TyDefId>,
     ) -> Type {
-        let substs = Substitution::build_for_def(db, def).fill_with_unknown().build();
-        let ty = db.ty(def.into()).subst(&substs);
+        let ty = TyBuilder::def_ty(db, def.into()).fill_with_unknown().build();
         Type::new(db, krate, def, ty)
     }
 
@@ -1785,13 +1783,10 @@ impl Type {
     }
 
     pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
-        let trait_ref = hir_ty::TraitRef {
-            trait_id: hir_ty::to_chalk_trait_id(trait_.id),
-            substitution: Substitution::build_for_def(db, trait_.id)
-                .push(self.ty.clone())
-                .fill(args.iter().map(|t| t.ty.clone()))
-                .build(),
-        };
+        let trait_ref = TyBuilder::trait_ref(db, trait_.id)
+            .push(self.ty.clone())
+            .fill(args.iter().map(|t| t.ty.clone()))
+            .build();
 
         let goal = Canonical {
             value: hir_ty::InEnvironment::new(self.env.env.clone(), trait_ref.cast(&Interner)),
@@ -1804,22 +1799,18 @@ impl Type {
     pub fn normalize_trait_assoc_type(
         &self,
         db: &dyn HirDatabase,
-        trait_: Trait,
         args: &[Type],
         alias: TypeAlias,
     ) -> Option<Type> {
-        let subst = Substitution::build_for_def(db, trait_.id)
+        let projection = TyBuilder::assoc_type_projection(db, alias.id)
             .push(self.ty.clone())
             .fill(args.iter().map(|t| t.ty.clone()))
             .build();
         let goal = Canonical::new(
             InEnvironment::new(
                 self.env.env.clone(),
                 AliasEq {
-                    alias: AliasTy::Projection(ProjectionTy {
-                        associated_ty_id: to_assoc_type_id(alias.id),
-                        substitution: subst,
-                    }),
+                    alias: AliasTy::Projection(projection),
                     ty: TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
                         .intern(&Interner),
                 }

crates/hir_ty/src/autoderef.rs

@@ -13,11 +13,9 @@ use log::{info, warn};
 
 use crate::{
     db::HirDatabase,
-    to_assoc_type_id, to_chalk_trait_id,
     traits::{InEnvironment, Solution},
-    utils::generics,
-    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, Interner,
-    ProjectionTy, Substitution, TraitRef, Ty, TyKind,
+    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, Interner, Ty,
+    TyBuilder, TyKind,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -57,21 +55,20 @@ fn deref_by_trait(
     };
     let target = db.trait_data(deref_trait).associated_type_by_name(&name![Target])?;
 
-    let generic_params = generics(db.upcast(), target.into());
-    if generic_params.len() != 1 {
-        // the Target type + Deref trait should only have one generic parameter,
-        // namely Deref's Self type
-        return None;
-    }
+    let projection = {
+        let b = TyBuilder::assoc_type_projection(db, target);
+        if b.remaining() != 1 {
+            // the Target type + Deref trait should only have one generic parameter,
+            // namely Deref's Self type
+            return None;
+        }
+        b.push(ty.goal.value.clone()).build()
+    };
 
     // FIXME make the Canonical / bound var handling nicer
 
-    let parameters =
-        Substitution::build_for_generics(&generic_params).push(ty.goal.value.clone()).build();
-
     // Check that the type implements Deref at all
-    let trait_ref =
-        TraitRef { trait_id: to_chalk_trait_id(deref_trait), substitution: parameters.clone() };
+    let trait_ref = projection.trait_ref(db);
     let implements_goal = Canonical {
         binders: ty.goal.binders.clone(),
         value: InEnvironment {
@@ -84,21 +81,16 @@ fn deref_by_trait(
     }
 
     // Now do the assoc type projection
-    let projection = AliasEq {
-        alias: AliasTy::Projection(ProjectionTy {
-            associated_ty_id: to_assoc_type_id(target),
-            substitution: parameters,
-        }),
+    let alias_eq = AliasEq {
+        alias: AliasTy::Projection(projection),
         ty: TyKind::BoundVar(BoundVar::new(
             DebruijnIndex::INNERMOST,
             ty.goal.binders.len(&Interner),
         ))
         .intern(&Interner),
     };
 
-    let obligation = projection.cast(&Interner);
-
-    let in_env = InEnvironment { goal: obligation, environment: ty.environment };
+    let in_env = InEnvironment { goal: alias_eq.cast(&Interner), environment: ty.environment };
 
     let canonical = Canonical {
         value: in_env,