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With the new design for option types, the fuser needs to fuse optional fields such that the option type of the field is pushed into the field's fusion type so we have fusion(...|none) instead of none|fusion(...). This problem was causing upcast to fail on such patterns. We've added test coverage to catch this.
nwt
approved these changes
May 2, 2026
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With the new design for option types, the fuser needs to fuse optional fields such that the option type of the field is pushed into the field's fusion type so we have fusion(...|none) instead of none|fusion(...). This problem was causing upcast to fail on such patterns. We've added test coverage to catch this.