Fix unnecessary_unwrap emitted twice in closure (#14763) (#14770)

The problem is that `check_fn` is triggered by both function and
closure, and `visit_expr` can visit expressions in another closures
within a function or closure.

So just skip walking in a inner closure.

changelog: Fix [`unnecessary_unwrap`] emitted twice in closure which
inside in a function or another closure.

Fixes: rust-lang/rust-clippy#14763

clippy_lints/src/unwrap.rs

@@ -292,6 +292,10 @@ impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx> {
         if expr.span.in_external_macro(self.cx.tcx.sess.source_map()) {
             return;
         }
+        // Skip checking inside closures since they are visited through `Unwrap::check_fn()` already.
+        if matches!(expr.kind, ExprKind::Closure(_)) {
+            return;
+        }
         if let Some(higher::If { cond, then, r#else }) = higher::If::hir(expr) {
             walk_expr(self, cond);
             self.visit_branch(expr, cond, then, false);