simplify fusion for arrays, sets, and maps#6949
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This commit simplifies type fusion for container types (i.e., arrays, sets, and maps) by moving the fusion-type wrapper from the inner types to the container type. There is no loss of information about subtypes because a container type completely identifies the types of the consituent elements so there is no need for the elements to also carry their subtypes, i.e., they are passed down from the parent to the children elements during a donwcast. Note that retaining the fusion types on the elements instead of the parent container would *not* work because empty containers would have nowhere to store the empty container type. Docs updates are forthcoming on a subsequent PR.
nwt
approved these changes
May 14, 2026
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This commit simplifies type fusion for container types (i.e., arrays, sets, and maps) by moving the fusion-type wrapper from the inner types to the container type. There is no loss of information about subtypes because a container type completely identifies the types of the consituent elements so there is no need for the elements to also carry their subtypes, i.e., they are passed down from the parent to the children elements during a donwcast. Note that retaining the fusion types on the elements instead of the parent container would not work because empty containers would have nowhere to store the empty container type.
Docs updates are forthcoming on a subsequent PR.