Add helper for resolving associated type of trait in infer

2 files changed, 25 insertions, 47 deletions

diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index d16f1eb46..62d5c8803 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -338,6 +338,24 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.table.resolve_ty_shallow(ty)
     }
 
+    fn resolve_associated_type(&mut self, inner_ty: Ty, assoc_ty: Option<TypeAliasId>) -> Ty {
+        match assoc_ty {
+            Some(res_assoc_ty) => {
+                let ty = self.table.new_type_var();
+                let projection = ProjectionPredicate {
+                    ty: ty.clone(),
+                    projection_ty: ProjectionTy {
+                        associated_ty: res_assoc_ty,
+                        parameters: Substs::single(inner_ty),
+                    },
+                };
+                self.obligations.push(Obligation::Projection(projection));
+                self.resolve_ty_as_possible(ty)
+            }
+            None => Ty::Unknown,
+        }
+    }
+
     /// Recurses through the given type, normalizing associated types mentioned
     /// in it by replacing them by type variables and registering obligations to
     /// resolve later. This should be done once for every type we get from some
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 2c296987c..6110f5abd 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -19,8 +19,8 @@ use crate::{
     method_resolution, op,
     traits::InEnvironment,
     utils::{generics, variant_data, Generics},
-    CallableDef, InferTy, IntTy, Mutability, Obligation, ProjectionPredicate, ProjectionTy, Substs,
-    TraitRef, Ty, TypeCtor, TypeWalk, Uncertain,
+    ApplicationTy, CallableDef, InferTy, IntTy, Mutability, Obligation, Substs, TraitRef, Ty,
+    TypeCtor, TypeWalk, Uncertain,
 };
 
 use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
@@ -95,21 +95,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::For { iterable, body, pat } => {
                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
 
-                let pat_ty = match self.resolve_into_iter_item() {
-                    Some(into_iter_item_alias) => {
-                        let pat_ty = self.table.new_type_var();
-                        let projection = ProjectionPredicate {
-                            ty: pat_ty.clone(),
-                            projection_ty: ProjectionTy {
-                                associated_ty: into_iter_item_alias,
-                                parameters: Substs::single(iterable_ty),
-                            },
-                        };
-                        self.obligations.push(Obligation::Projection(projection));
-                        self.resolve_ty_as_possible(pat_ty)
-                    }
-                    None => Ty::Unknown,
-                };
+                let pat_ty =
+                    self.resolve_associated_type(iterable_ty, self.resolve_into_iter_item());
 
                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
                 self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
@@ -284,40 +271,13 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::Await { expr } => {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
-                let ty = match self.resolve_future_future_output() {
-                    Some(future_future_output_alias) => {
-                        let ty = self.table.new_type_var();
-                        let projection = ProjectionPredicate {
-                            ty: ty.clone(),
-                            projection_ty: ProjectionTy {
-                                associated_ty: future_future_output_alias,
-                                parameters: Substs::single(inner_ty),
-                            },
-                        };
-                        self.obligations.push(Obligation::Projection(projection));
-                        self.resolve_ty_as_possible(ty)
-                    }
-                    None => Ty::Unknown,
-                };
+                let ty =
+                    self.resolve_associated_type(inner_ty, self.resolve_future_future_output());
                 ty
             }
             Expr::Try { expr } => {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
-                let ty = match self.resolve_ops_try_ok() {
-                    Some(ops_try_ok_alias) => {
-                        let ty = self.table.new_type_var();
-                        let projection = ProjectionPredicate {
-                            ty: ty.clone(),
-                            projection_ty: ProjectionTy {
-                                associated_ty: ops_try_ok_alias,
-                                parameters: Substs::single(inner_ty),
-                            },
-                        };
-                        self.obligations.push(Obligation::Projection(projection));
-                        self.resolve_ty_as_possible(ty)
-                    }
-                    None => Ty::Unknown,
-                };
+                let ty = self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok());
                 ty
             }
             Expr::Cast { expr, type_ref } => {