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Geoff RomerandChandler Carruth
49c7288619
- A function with a return declaration always has exactly one `ReturnSlotPattern`, representing the whole return declaration (whereas previously that was omitted for value and reference returns). - The `ReturnSlotPattern` always has a subpattern with the same form. `OutParamPattern` already plays that role for initializing forms, and `TuplePattern` will play that role for tuple forms. This change introduces `ValueReturnPattern` and `RefReturnPattern` to represent value and reference return forms. - As before, the `ReturnSlotPattern` has a corresponding `ReturnSlot` that represents the output that is initialized by a `return` statement. Its structure parallels the structure of the `ReturnSlotPattern`, so we need `ValueReturn` and `RefReturn` insts that correspond to `ValueReturnPattern` and `RefReturnPattern`. This is a step toward supporting generic return forms, where the `ReturnSlotPattern`'s subpattern may be an action: this change ensures that evaluating the action for a specific form produces the same SemIR as if the form were concrete to begin with. More speculatively, this should simplify the implementation of `return` statements with compound return forms. --------- Co-authored-by: Chandler Carruth <chandlerc@gmail.com>