#16232: Add setField to HasField -------------------------------------+------------------------------------- Reporter: adamgundry | Owner: adamgundry Type: feature request | Status: new Priority: normal | Milestone: 8.10.1 Component: Compiler (Type | Version: 8.7 checker) | Resolution: | Keywords: ORF Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by adamgundry): * owner: (none) => adamgundry Comment:
I suggest taking the direct path, and generate an update function for each field.
Sorry, to be clear, do you mean the approach of generating renamed syntax at definition sites?
Its more work than Matthew says because we may need to evaluate the argument (for strict constructors) or unbox it (if the argument is UNPACKed).
Exactly, perhaps my example didn't do a good job of conveying the awkward points here. Let me see if I understand correctly what generating Core directly needs to do in the general case: * When we pattern match in Core, we match on the *worker* (binding its existential tyvars, theta and the arguments as given by `dataConInstSig`). * We can use `dataConBoxer` to build let-bindings for the arguments to the wrapper out of the bound variables from matching on the worker. * We need to construct an application of the *wrapper* to appropriate boxed arguments, replacing the one that corresponds to the field being updated with the new value. I don't understand very clearly how to do this. In particular, I'm not sure how to figure out the order in which to instantiate type variables and dictionaries in the wrapper's type. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16232#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler