# API Changes
## `swc_ecma_utils`
### Renames
- `find_ids` => `find_pat_ids`
- `prepend` => `prepend_stmt`
- `as_bool` => `cast_to_bool`
- `as_number` => `as_pure_number`
- `as_string` => `cast_to_string`
- (`as_pure_bool`, `cast_to_number` is not renamed)
- `UsageFinder` => `IdentUsageFinder`.
- `IdentFinder` => `IdentRefFinder`.
## Changes
- Re-export of `HANDLER` from `swc_common::errors` is removed. Use `swc_common::error::HANDLER` instead.
- Re-export of `Id` from `swc_ecma_ast` is removed. Use `swc_ecma_ast::Id` instead.
- `ExprCtx` is used for apis related to `Expr`.
- `preserve_effects` is now a method of `ExprCtx`. It was a top-level function.
- `extract_side_effects_to` is now a method of `ExprCtx`. It was a top-level function.
- `IdentUsageFinder` (previously `UsageFinder`) now takes `Id` instead of `Ident`.
- `IdentRefFinder` (previously `IdentFinder`) now takes `Id` instead of `Ident`.
- `ExprExt::is_ident_ref_to` is removed.
- `Expr::is_global_ref_to` is added.
- `:🆔:id` is removed. Use `Ident::to_id()` instead.
- We don't need a list of bindings to check if an identifier is unresolved.
- Checking if an identifier is unresolved is now one CPU instruction.
- Previously it was one hashmap operation.
- This PR also improves performance, by removing the hashmaps mentioned above.
- We now remap parameters using a new syntax context. This is required because we may copy functions, and it can result in duplicated variables with respect to the span hygiene.
- We now visit the sequence expression generated by inlining. This is to improve performance in some cases.
- We now remove variables from variable statements if it's identical to a parameter declared in the function.
- IIFE evaluation is now aware of `this` being different for member expressions.
- We now have more logic for detecting simple functions.
