2 files changed, 11 insertions, 9 deletions

diff --git a/crates/ra_hir/src/either.rs b/crates/ra_hir/src/either.rs
index 71c53ebc0..439e6ec87 100644
--- a/crates/ra_hir/src/either.rs
+++ b/crates/ra_hir/src/either.rs
@@ -25,6 +25,12 @@ impl<A, B> Either<A, B> {
             Either::B(b) => Either::B(f2(b)),
         }
     }
+    pub fn map_a<U, F>(self, f: F) -> Either<U, B>
+    where
+        F: FnOnce(A) -> U,
+    {
+        self.map(f, |it| it)
+    }
     pub fn a(self) -> Option<A> {
         match self {
             Either::A(it) => Some(it),
diff --git a/crates/ra_hir/src/source_binder.rs b/crates/ra_hir/src/source_binder.rs
index 55eb7da35..df67d2c39 100644
--- a/crates/ra_hir/src/source_binder.rs
+++ b/crates/ra_hir/src/source_binder.rs
@@ -309,15 +309,11 @@ impl SourceAnalyzer {
             crate::Resolution::LocalBinding(it) => {
                 // We get a `PatId` from resolver, but it actually can only
                 // point at `BindPat`, and not at the arbitrary pattern.
-                let pat_ptr = self.body_source_map.as_ref()?.pat_syntax(it)?;
-                let pat_ptr = match pat_ptr {
-                    Either::A(pat) => {
-                        let pat: AstPtr<ast::BindPat> =
-                            pat.cast_checking_kind(|kind| kind == BIND_PAT).unwrap();
-                        Either::A(pat)
-                    }
-                    Either::B(self_param) => Either::B(self_param),
-                };
+                let pat_ptr = self
+                    .body_source_map
+                    .as_ref()?
+                    .pat_syntax(it)?
+                    .map_a(|ptr| ptr.cast::<ast::BindPat>().unwrap());
                 PathResolution::LocalBinding(pat_ptr)
             }
             crate::Resolution::GenericParam(it) => PathResolution::GenericParam(it),