add struct_id accessor, refactor unnecessary skip_binders calls

Author: basil-cow

chalk-integration/src/program.rs

@@ -6,7 +6,7 @@ use chalk_ir::tls;
 use chalk_ir::{
     debug::SeparatorTraitRef, AliasTy, ApplicationTy, AssocTypeId, Goal, Goals, ImplId, Lifetime,
     Parameter, ProgramClause, ProgramClauseImplication, ProgramClauses, StructId, Substitution,
-    TraitId, Ty, TyData, TypeName,
+    TraitId, Ty, TypeName,
 };
 use chalk_rust_ir::{
     AssociatedTyDatum, AssociatedTyValue, AssociatedTyValueId, ImplDatum, ImplType, StructDatum,
@@ -308,16 +308,8 @@ impl RustIrDatabase<ChalkIr> for Program {
         // Look for an impl like `impl Send for Foo` where `Foo` is
         // the struct.  See `push_auto_trait_impls` for more.
         self.impl_data.values().any(|impl_datum| {
-            let impl_trait_ref = &impl_datum.binders.skip_binders().trait_ref;
-            impl_trait_ref.trait_id == auto_trait_id
-                && match impl_trait_ref.self_type_parameter(interner).data(interner) {
-                    TyData::Apply(apply) => match apply.name {
-                        TypeName::Struct(id) => id == struct_id,
-                        _ => false,
-                    },
-
-                    _ => false,
-                }
+            impl_datum.trait_id() == auto_trait_id
+                && impl_datum.self_type_struct_id(interner) == Some(struct_id)
         })
     }
 

chalk-rust-ir/src/lib.rs

@@ -37,6 +37,22 @@ impl<I: Interner> ImplDatum<I> {
     pub fn trait_id(&self) -> TraitId<I> {
         self.binders.skip_binders().trait_ref.trait_id
     }
+
+    pub fn self_type_struct_id(&self, interner: &I) -> Option<StructId<I>> {
+        match self
+            .binders
+            .skip_binders()
+            .trait_ref
+            .self_type_parameter(interner)
+            .data(interner)
+        {
+            TyData::Apply(apply) => match apply.name {
+                TypeName::Struct(id) => Some(id),
+                _ => None,
+            },
+            _ => None,
+        }
+    }
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, HasInterner, Fold)]

chalk-solve/src/wf.rs

@@ -612,20 +612,10 @@ impl WfWellKnownGoals {
     ) -> Option<Goal<I>> {
         let interner = db.interner();
 
-        let struct_id = if let TyData::Apply(ApplicationTy {
-            name: TypeName::Struct(struct_id),
-            ..
-        }) = impl_datum
-            .binders
-            .skip_binders()
-            .trait_ref
-            .self_type_parameter(interner)
-            .data(interner)
-        {
-            *struct_id
-        } else {
+        let struct_id = match impl_datum.self_type_struct_id(interner) {
+            Some(id) => id,
             // Drop can only be implemented on a nominal type
-            return Some(GoalData::CannotProve(()).intern(interner));
+            None => return Some(GoalData::CannotProve(()).intern(interner)),
         };
 
         let mut gb = GoalBuilder::new(db);