remove warnings

Author: alibektas

crates/hir-ty/src/lib.rs

@@ -1053,8 +1053,11 @@ pub fn known_const_to_ast(
 #[derive(Debug, Copy, Clone)]
 pub(crate) enum DeclOrigin {
     // from an `if let` expression
-    LetExpr,
-    // from `let x = ..`
+    // Due to the limited use of `DeclOrigin` it has so far been
+    // necessary to have the `LetExpr` variant. However, to have the
+    // identical struct to its rustc counterpart, we keep this variant here.
+    // LetExpr,
+    /// from `let x = ..`
     LocalDecl,
 }