Auto merge of #14755 - poliorcetics:clippy-fixes, r=Veykril

Fix: a TODO and some clippy fixes

- fix(todo): implement IntoIterator for ArenaMap<IDX, V>
- chore: remove unused method
- fix: remove useless `return`s
- fix: various clippy lints
- fix: simplify boolean test to a single negation

crates/syntax/src/ast/expr_ext.rs

@@ -370,8 +370,7 @@ impl ast::BlockExpr {
         match parent.kind() {
             FOR_EXPR | IF_EXPR => parent
                 .children()
-                .filter(|it| ast::Expr::can_cast(it.kind()))
-                .next()
+                .find(|it| ast::Expr::can_cast(it.kind()))
                 .map_or(true, |it| it == *self.syntax()),
             LET_ELSE | FN | WHILE_EXPR | LOOP_EXPR | CONST_BLOCK_PAT => false,
             _ => true,