**Description:**
This PR is to prepare removal of `string-cache`. Actually, this PR does not remove it. Instead, this PR only removes direct usages of `js_word!`s, especially in patterns.
**Related issue:**
- #4946.
**Description:**
## Bugfixes
- Exported `let`/`var` declarations in TypeScript namespaces should be mutable.
- Fix missing declaration of complex exported patterns in TypeScript namespaces.
- Preserve concrete TS namespaces.
## New Features
- Introducing [Verbatim Module Syntax](https://www.typescriptlang.org/tsconfig#verbatimModuleSyntax).
- Enum value will now be inlined whenever possible within a single module, optimizing runtime performance.
- Constant enums will be automatically eliminated when feasible, This can reduce bundle size.
- Added support for cross-referencing enum values.
## Deprecated
`TsEnumConfig` is deprecated
- The `treat_const_enum_as_enum` transform option is deprecated.
- The `ts_enum_is_readonly` assumption option is deprecated.
**BREAKING CHANGE:**
TypeScript Config is changed.
**Related issue:**
- Closes#5197
- Closes#5259
- Closes#7177
- Closes#7453
- Closes#7676
- Closes#7681
- Closes#7791
- Closes#7961
**Description:**
- `jsc.experimental.keepImportAssertions` is renamed to `jsc.experimental.keepImportAttributes`.
- `jsc.experimental.emitAssertForImportAttributes` is added.
**Related issue:**
- Closes#7908
**BREAKING CHANGE:**
IMPORTANT NOTE: Users of decorators are recommended to configure `"useDefineForClassFields": false` to ensure that your code is properly transpiled.
**Related issue:**
- Closes https://github.com/swc-project/swc/issues/6985.
# 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.
swc_ecma_ast:
- Split `MemberExpr` into `MemberExpr` and `SuperPropExpr`.
- Use `Box<Expr>` for `MemberExpr.obj`.
- Use ad-hoc type for `MemberExpr.prop`.
- Use ad-hoc type for `SuperPropExpr.prop`.
- Use `Callee` instead of `ExprOrSpread` for `CallExpr`.
- Simplify types for meta property expressions.
swc_ecma_transforms_base:
- `hygiene`: Skip checking a symbol if we are sure that it will be discarded.
swc_ecma_laoder:
- Optimize `NodeModulesResolver` by trying `.js` first.
