Unused variable inside a block is not treeshaken if not at the start of the body

If an unused variable is declared somewhere in the middle of the function body, it will not be removed. Seems to apply to block statements in general, any non treeshaken declaration will prevent any further declarations within the block from being removed.

https://esbuild.github.io/try/#YgAwLjE5LjMAe21pbmlmeTogdHJ1ZSwgZXh0ZXJuYWw6IFsid2hlcmV2ZXIiXSwgYnVuZGxlOnRydWUsIGZvcm1hdDogImVzbSIsIHRyZWVTaGFraW5nOiB0cnVlfQBlAGVudHJ5LmpzAGltcG9ydCAqIGFzICQgZnJvbSAid2hlcmV2ZXIiOwoKZXhwb3J0IGZ1bmN0aW9uIE1haW4oKSB7CiAgICAgICBjb25zdCBhID0gMjsKICAgICAgIGNvbnN0IGZvbyA9ICQKICAgICAgIGNvbnN0IGIgPSAzCgogICAgICAgaWYgKGZvbykgewogICAgICAgIGNvbnN0IGMgPSA0OwogICAgICAgIGZvby50b1N0cmluZygpCiAgICAgICAgY29uc3QgZCA9IDUKICAgICAgIH0KICAgICAgIHJldHVybiBmb28KfQ

Start with the linked esbuild playground reproduction and inspect the minified output for the function and block declarations shown there. Trace the tree-shaking logic for declarations after a retained declaration, then add a regression test covering this case. Done means the unused declarations are removed without changing the remaining behavior.

Written by the indexing model from the issue text.