1 files changed, 1 insertions, 0 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index e39f06e68..d1a9d7411 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -400,6 +400,7 @@ impl SubstsBuilder {
 
     pub fn fill(mut self, filler: impl Iterator<Item = Ty>) -> Self {
         self.vec.extend(filler.take(self.remaining()));
+        assert_eq!(self.remaining(), 0);
         self
     }