Changes between Initial Version and Version 1 of Ticket #14749


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Timestamp:
Feb 1, 2018 9:14:41 AM (21 months ago)
Author:
simonpj
Comment:

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  • Ticket #14749 – Description

    initial v1  
    3131With a stage-1 compiler with DEBUG enabled, this program yields a Lint error in all recent versions of GHC. (NB: Lint, not an assertion failure.)
    3232
    33 With stage-2 it succeeds, and passes Lint.  But an apparently unrelated patch makes it fail Lint even in stage 2.  I conclude that the bug is not in the unrelated patch; it is somehow there all along.
     33With stage-2 it succeeds, and passes Lint. Reason: without DEBUG the output of the typechecker is not Linted until after a run of the `CoreOpt`; and that simplifies the coercions; which somehow eliminates the Lint error.
     34
     35I added`-ddump-ds-preopt` to made the pre-core-opt dump optional -- it is sometimes useful in a non-DEBUG compiler.  But that makes Lint run on the pre-core-opt code, and that shows up the bug always.
     36But an apparently unrelated patch makes it fail Lint even in stage 2.  So it's kind of harmless; but a clear bug that we should fix. 
    3437
    3538I'll mark T13822 as expect-broken; you can re-enable it when this ticket is fixed.