1. 25 Nov, 2013 1 commit
    • Simon Peyton Jones's avatar
      Another raft of Template Haskell clean-up · 51deeb0d
      Simon Peyton Jones authored
      The handling of typed and untyped brackets was extremely convoluted,
      partly because of the evolutionary history.  I've tidied it all up.
      
      See Note [How brackets and nested splices are handled] in TcSplice
      for the full story
      
      Main changes:
      
       * Untyped brackets: after the renamer, HsRnBracketOut carries
         PendingRnSplices for splices in untyped brackets.  In the
         typechecker, these pending splices are typechecked quite
         straigtforwardly, with no ps_var nonsense.
      
       * Typed brackets: after the renamer typed brackest still look
         like HsBracket. The type checker does the ps_var thing.
      
       * In TcRnTypes.ThStage, the Brack constructor, we distinguish
         the renaming from typehecking pending-stuff.  Much more
         perspicuous!
      
       * The "typed" flag is in HsSpliceE, not in HsSplice, because
         only expressions can be typed.  Patterns, types, declarations
         cannot.
      
      There is further improvement to be done to make the handling of
      declaration splices more uniform.
      51deeb0d
  2. 22 Nov, 2013 2 commits
    • Simon Peyton Jones's avatar
      ea49c015
    • Simon Peyton Jones's avatar
      A raft of changes driven by Trac #8540 · 78814882
      Simon Peyton Jones authored
      The root cause of #8450 is that the new Template Haskell story, with
      the renamer doing more of the work of Template Haskell, wasn't dealing
      correctly with the keepAlive problem.  Consider
          g = ..blah...
          f = [| g |]
      Then f's RHS refers to g's name but not to g, so g was being discarded
      as dead code.
      
      Fixing this sucked me into a deep swamp of understanding how all the moving
      parts of hte new Template Haskell fit together, leading to a large collection
      of related changes and better documentation.  Specifically:
      
      * Instead of putting the TH level of a binder in the LocalRdrEnv, there
        is now a separate field
            tcl_th_bndrs :: NameEnv (TopLevelFlag, ThLevel)
        in the TcLclEnv, which records for each binder
           a) whether it is syntactically a top-level binder or not
           b) its TH level
        This deals uniformly with top-level and non-top-level binders, which was
        previously dealt with via greviously-delicate meddling with Internal and
        External Names.  Much better.
      
      * As a result I could remove the tct_level field of ATcId.
      
      * There are consequential changes in TcEnv too, which must also extend the
        level bindings.  Again, more clarity.
      
        I renamed TcEnv.tcExtendTcTyThingEnv to tcExtendKindEnv2, since it's only used
        during kind inference, for (AThing kind) and APromotionErr; and that is
        relevant to whether we want to extend the tcl_th_bndrs field (no).
      
      * I de-crufted the code in RnEnv.extendGlobalRdrEnv, by getting rid of the
        qual_gre code which said "Seems like 5 times as much work as it deserves!".
        Instead, RdrName.pickGREs makes the Internal names shadow External ones.
      
      * I moved the checkThLocalName cross-stage test to finishHsVar; previously
        we weren't doing the test at all in the OpApp case!
      
      * Quite a few changes (shortening the code) in the cross-stage checking code
        in TcExpr and RnSplice, notably to move the keepAlive call to the renamer
      
      One leftover piece:
      
      * In TcEnv I removed tcExtendGhciEnv and refactored
        tcExtendGlobalTyVars; this is really related to the next commit, but
        it was too hard to disentangle.
      78814882
  3. 06 Nov, 2013 1 commit
  4. 04 Oct, 2013 8 commits