Prune empty case blocks before a default (original) (raw)

I think there's an opportunity to further optimize switch statements by removing empty case blocks before a default.

Input:

switch (globalThis.foo) { case 'first': { console.log('first'); } case 'second': default: { console.log('default'); } }

Expected output:

switch (globalThis.foo) { case 'first': console.log('first'); default: console.log('default'); }

Actual output (0.27.1):

switch (globalThis.foo) { case 'first': console.log('first'); case 'second': // Unnecessary! default: console.log('default'); }

Playground link

I think you do need to keep case statements which contain expressions (case getSecond(): ...) as that's probably important for execution order and potential side effects. But I think any literal values should be safe to remove, and that's likely the most common case with switch statements.