• elaforge's avatar
    Rearrange error msgs and add section markers (Trac #11014). · c05fddde
    elaforge authored
    This puts the "Relevant bindings" section at the end.
    
    It uses a TcErrors.Report Monoid to divide messages by importance and
    then mappends them together.  This is not the most efficient way since
    there are various intermediate Reports and list appends, but it probably
    doesn't matter since error messages shouldn't get that large, and are
    usually prepended.  In practice, everything is `important` except
    `relevantBindings`, which is `supplementary`.
    
    ErrMsg's errMsgShortDoc and errMsgExtraInfo were extracted into ErrDoc,
    which has important, context, and suppelementary fields.  Each of those
    three sections is marked with a bullet character, '•' on unicode
    terminals and '*' on ascii terminals.  Since this breaks tons of tests,
    I also modified testlib.normalise_errmsg to strip out '•'s.
    
    --- Additional notes:
    
    To avoid prepending * to an empty doc, I needed to filter empty docs.
    This seemed less error-prone than trying to modify everyone who produces
    SDoc to instead produce Maybe SDoc.  So I added `Outputable.isEmpty`.
    Unfortunately it needs a DynFlags, which is kind of bogus, but otherwise
    I think I'd need another Empty case for SDoc, and then it couldn't be a
    newtype any more.
    
    ErrMsg's errMsgShortString is only used by the Show instance, which is
    in turn only used by Show HscTypes.SourceError, which is in turn only
    needed for the Exception instance.  So it's probably possible to get rid
    of errMsgShortString, but that would a be an unrelated cleanup.
    
    Fixes #11014.
    
    Test Plan: see above
    
    Reviewers: austin, simonpj, thomie, bgamari
    
    Reviewed By: thomie, bgamari
    
    Subscribers: simonpj, nomeata, thomie
    
    Differential Revision: https://phabricator.haskell.org/D1427
    
    GHC Trac Issues: #11014
    c05fddde
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