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Jon Ross-Perkins
91f0c23124
Building on #3636 which handles the general import case, add special casing for namespaces. Namespaces can be combined cross-IR, so it's a little more complex. The implementation adds import_id to the Namespace instruction as a reference to find the original using the normal structure. This is achieved by moving the name_id to NameScope to free up space. --- I considered a few alternatives... I considered adding import_id to NameScope, but: 1. It's more consistent with things such as Function or Class that provide name_id on the info object rather than the instruction. 2. I thought it more likely that there would be more NameScope cases that might want a name_id rather than the import_id, since ImportRef will typically be used. I considered putting the import source (cross-ref IR id + inst id) on the NameScope versus a separate ImportRef, which seems like the strongest argument towards the NameScope approach because it removes an instruction. That just felt inconsistent though, and the overhead of instruction-per-imported-namespace should be low (theoretically few namespaces should be used). Plus I feel a bit odd adding two generally-unused ids to NameScope. A specialized Namespace structure could also have been created to store the import_id, but that would add an indirection to the NameScope.