Adapt to Coq PR #18591: better refolding of List.app inducing "simpl never" now better respected #224
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…curatedly. The change is however indirect: - Coq PR #18591 fixes a lack of refolding of fixpoints; - as a consequence, some calls to "simpl" on subterms start to respect "simpl never" as required; - this impacts "injection" (here the "[]" intro-pattern) as "injection" calls "simpl" on the subterms it generates.
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Tactic
injection(called here via the introduction pattern[]) routinely callssimplto simplify the application of the underlying injectors to the terms to invert. We modify two cases inMM2_ZERO_HALTING_to_SSTS01.vwhere, after coq/coq#18591, these calls tosimplstop reducing[] ++ lintoldue toList.app(i.e.++) being declaredsimpl never.The reason
simplformerly reduced[] ++ lis thatsimplcalled on a subterm of the forminjector ([a] ++ l])wrongly failed to refold the underlying occurrences ofList.app, producing instead(fix f := ... code of List.app ...) [] l, leading to miss thesimpl neverrequest.We fix the script by explicitly unfolding
++in the two cases where[] ++ lwas produced.I tried at some time to understand if the use of
simpl neverin the file was actually motivated byList.appbeing not enough refolded, but apparently no. So, I kept thesimpl neverand locally modified instead the two failing places.If I'm correct, the change is backwards compatible. So, if the change looks ok to you, it can be merged as soon as now.