fix

src/Init/Data/Array/Lemmas.lean

diff --git a/src/Init/Data/Array/Lemmas.lean b/src/Init/Data/Array/Lemmas.lean
index bfe25ca..3eee4ef 100644
--- a/src/Init/Data/Array/Lemmas.lean
+++ b/src/Init/Data/Array/Lemmas.lean
@@ -1508,7 +1508,7 @@
 
 /-! ### singleton -/
 
-@[simp] theorem singleton_def (v : α) : singleton v = #[v] := rfl
+@[simp] theorem singleton_def (v : α) : Array.singleton v = #[v] := rfl
 
 /-! ### append -/