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[compiler] Prune all unused array destructure items during DCE #31603

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@josephsavona josephsavona commented Nov 21, 2024

Stack from ghstack (oldest at bottom):

We didn't originally support holes within array patterns, so DCE was only able to prune unused items from the end of an array pattern. Now that we support holes we can replace any unused item with a hole, and then just prune the items to the last identifier/spread entry.

Note: this was motivated by finding useState where either the state or setState go unused — both are strong indications that you're violating the rules in some way. By DCE-ing the unused portions of the useState destructuring we can easily check if you're ignoring either value.

We didn't originally support holes within array patterns, so DCE was only able to prune unused items from the end of an array pattern. Now that we support holes we can replace any unused item with a hole, and then just prune the items to the last identifier/spread entry.

Note: this was motivated by finding useState where either the state or setState go unused — both are strong indications that you're violating the rules in some way. By DCE-ing the unused portions of the useState destructuring we can easily check if you're ignoring either value.

[ghstack-poisoned]
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josephsavona added a commit that referenced this pull request Nov 21, 2024
We didn't originally support holes within array patterns, so DCE was only able to prune unused items from the end of an array pattern. Now that we support holes we can replace any unused item with a hole, and then just prune the items to the last identifier/spread entry.

Note: this was motivated by finding useState where either the state or setState go unused — both are strong indications that you're violating the rules in some way. By DCE-ing the unused portions of the useState destructuring we can easily check if you're ignoring either value.

ghstack-source-id: 0721ece5e602e3550c0891d8b9e1291eebed8e4b
Pull Request resolved: #31603
@facebook-github-bot facebook-github-bot added CLA Signed React Core Team Opened by a member of the React Core Team labels Nov 21, 2024
… DCE"

We didn't originally support holes within array patterns, so DCE was only able to prune unused items from the end of an array pattern. Now that we support holes we can replace any unused item with a hole, and then just prune the items to the last identifier/spread entry.

Note: this was motivated by finding useState where either the state or setState go unused — both are strong indications that you're violating the rules in some way. By DCE-ing the unused portions of the useState destructuring we can easily check if you're ignoring either value.

[ghstack-poisoned]
josephsavona added a commit that referenced this pull request Nov 21, 2024
We didn't originally support holes within array patterns, so DCE was only able to prune unused items from the end of an array pattern. Now that we support holes we can replace any unused item with a hole, and then just prune the items to the last identifier/spread entry.

Note: this was motivated by finding useState where either the state or setState go unused — both are strong indications that you're violating the rules in some way. By DCE-ing the unused portions of the useState destructuring we can easily check if you're ignoring either value.

ghstack-source-id: f13c5cc6df9ba3433131ac4a1e070d3769c88147
Pull Request resolved: #31603
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Nice!

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