1. 02 May, 2016 1 commit
    • Facundo Domínguez's avatar
      StaticPointers: Allow closed vars in the static form. · 36d29f7c
      Facundo Domínguez authored
      Summary:
      With this patch closed variables are allowed regardless of whether
      they are bound at the top level or not.
      
      The FloatOut pass is always performed. When optimizations are
      disabled, only expressions that go to the top level are floated.
      Thus, the applications of the StaticPtr data constructor are always
      floated.
      
      The CoreTidy pass makes sure the floated applications appear in the
      symbol table of object files. It also collects the floated bindings
      and inserts them in the static pointer table.
      
      The renamer does not check anymore if free variables appearing in the
      static form are top-level. Instead, the typechecker looks at the
      tct_closed flag to decide if the free variables are closed.
      
      The linter checks that applications of StaticPtr only occur at the
      top of top-level bindings after the FloatOut pass.
      
      The field spInfoName of StaticPtrInfo has been removed. It used to
      contain the name of the top-level binding that contains the StaticPtr
      application. However, this information is no longer available when the
      StaticPtr is constructed, as the binding name is determined now by the
      FloatOut pass.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, simonpj, austin, hvr, bgamari
      
      Reviewed By: simonpj
      
      Subscribers: thomie, mpickering, mboes
      
      Differential Revision: https://phabricator.haskell.org/D2104
      
      GHC Trac Issues: #11656
      36d29f7c
  2. 15 Apr, 2016 1 commit
    • niteria's avatar
      Kill some unnecessary varSetElems · 928d7473
      niteria authored
      When you do `varSetElems (tyCoVarsOfType x)` it's equivalent to
      `tyCoVarsOfTypeList x`.
      
      Why? If you look at the implementation:
      ```
      tyCoVarsOfTypeList ty = runFVList $ tyCoVarsOfTypeAcc ty
      tyCoVarsOfType ty = runFVSet $ tyCoVarsOfTypeAcc ty
      ```
      they use the same helper function. The helper function returns a
      deterministically ordered list and a set. The only difference
      between the two is which part of the result they take. It is redundant
      to take the set and then immediately convert it to a list.
      
      This helps with determinism and we eventually want to replace the uses
      of `varSetElems` with functions that don't leak the values of uniques.
      This change gets rid of some instances that are easy to kill.
      
      I chose not to annotate every place where I got rid of `varSetElems`
      with a comment about non-determinism, because once we get rid of
      `varSetElems` it will not be possible to do the wrong thing.
      
      Test Plan: ./validate
      
      Reviewers: goldfire, austin, simonmar, bgamari, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D2115
      
      GHC Trac Issues: #4012
      928d7473
  3. 24 Mar, 2016 1 commit
    • Ben Gamari's avatar
      ErrUtils: Add timings to compiler phases · 8048d51b
      Ben Gamari authored and Ben Gamari's avatar Ben Gamari committed
      This adds timings and allocation figures to the compiler's output when
      run with `-v2` in an effort to ease performance analysis.
      
      Todo:
        * Documentation
        * Where else should we add these?
        * Perhaps we should remove some of the now-arguably-redundant
          `showPass` occurrences where they are
        * Must we force more?
        * Perhaps we should place this behind a `-ftimings` instead of `-v2`
      
      Test Plan: `ghc -v2 Test.hs`, look at the output
      
      Reviewers: hvr, goldfire, simonmar, austin
      
      Reviewed By: simonmar
      
      Subscribers: angerman, michalt, niteria, ezyang, thomie
      
      Differential Revision: https://phabricator.haskell.org/D1959
      8048d51b
  4. 27 Feb, 2016 1 commit
  5. 18 Jan, 2016 1 commit
    • Jan Stolarek's avatar
      Replace calls to `ptext . sLit` with `text` · b8abd852
      Jan Stolarek authored
      Summary:
      In the past the canonical way for constructing an SDoc string literal was the
      composition `ptext . sLit`.  But for some time now we have function `text` that
      does the same.  Plus it has some rules that optimize its runtime behaviour.
      This patch takes all uses of `ptext . sLit` in the compiler and replaces them
      with calls to `text`.  The main benefits of this patch are clener (shorter) code
      and less dependencies between module, because many modules now do not need to
      import `FastString`.  I don't expect any performance benefits - we mostly use
      SDocs to report errors and it seems there is little to be gained here.
      
      Test Plan: ./validate
      
      Reviewers: bgamari, austin, goldfire, hvr, alanz
      
      Subscribers: goldfire, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D1784
      b8abd852
  6. 08 Jan, 2016 1 commit
    • Simon Marlow's avatar
      Enable stack traces with ghci -fexternal-interpreter -prof · 6be09e88
      Simon Marlow authored
      Summary:
      The main goal here is enable stack traces in GHCi.  After this change,
      if you start GHCi like this:
      
        ghci -fexternal-interpreter -prof
      
      (which requires packages to be built for profiling, but not GHC
      itself) then the interpreter manages cost-centre stacks during
      execution and can produce a stack trace on request.  Call locations
      are available for all interpreted code, and any compiled code that was
      built with the `-fprof-auto` familiy of flags.
      
      There are a couple of ways to get a stack trace:
      
      * `error`/`undefined` automatically get one attached
      * `Debug.Trace.traceStack` can be used anywhere, and prints the current
        stack
      
      Because the interpreter is running in a separate process, only the
      interpreted code is running in profiled mode and the compiler itself
      isn't slowed down by profiling.
      
      The GHCi debugger still doesn't work with -fexternal-interpreter,
      although this patch gets it a step closer.  Most of the functionality
      of breakpoints is implemented, but the runtime value introspection is
      still not supported.
      
      Along the way I also did some refactoring and added type arguments to
      the various remote pointer types in `GHCi.RemotePtr`, so there's
      better type safety and documentation in the bridge code between GHC
      and ghc-iserv.
      
      Test Plan: validate
      
      Reviewers: bgamari, ezyang, austin, hvr, goldfire, erikd
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1747
      
      GHC Trac Issues: #11047, #11100
      6be09e88
  7. 21 Dec, 2015 1 commit
    • Simon Marlow's avatar
      Maintain cost-centre stacks in the interpreter · c8c44fd9
      Simon Marlow authored
      Summary:
      Breakpoints become SCCs, so we have detailed call-stack info for
      interpreted code.  Currently this only works when GHC is compiled with
      -prof, but D1562 (Remote GHCi) removes this constraint so that in the
      future call stacks will be available without building your own GHCi.
      
      How can you get a stack trace?
      
      * programmatically: GHC.Stack.currentCallStack
      * I've added an experimental :where command that shows the stack when
        stopped at a breakpoint
      * `error` attaches a call stack automatically, although since calls to
        `error` are often lifted out to the top level, this is less useful
        than it might be (ImplicitParams still works though).
      * Later we might attach call stacks to all exceptions
      
      Other related changes in this diff:
      
      * I reduced the number of places that get ticks attached for
        breakpoints.  In particular there was a breakpoint around the whole
        declaration, which was often redundant because it bound no variables.
        This reduces clutter in the stack traces and speeds up compilation.
      
      * I tidied up some RealSrcSpan stuff in InteractiveUI, and made a few
        other small cleanups
      
      Test Plan: validate
      
      Reviewers: ezyang, bgamari, austin, hvr
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1595
      
      GHC Trac Issues: #11047
      c8c44fd9
  8. 11 Dec, 2015 1 commit
    • eir@cis.upenn.edu's avatar
      Add kind equalities to GHC. · 67465497
      eir@cis.upenn.edu authored
      This implements the ideas originally put forward in
      "System FC with Explicit Kind Equality" (ICFP'13).
      
      There are several noteworthy changes with this patch:
       * We now have casts in types. These change the kind
         of a type. See new constructor `CastTy`.
      
       * All types and all constructors can be promoted.
         This includes GADT constructors. GADT pattern matches
         take place in type family equations. In Core,
         types can now be applied to coercions via the
         `CoercionTy` constructor.
      
       * Coercions can now be heterogeneous, relating types
         of different kinds. A coercion proving `t1 :: k1 ~ t2 :: k2`
         proves both that `t1` and `t2` are the same and also that
         `k1` and `k2` are the same.
      
       * The `Coercion` type has been significantly enhanced.
         The documentation in `docs/core-spec/core-spec.pdf` reflects
         the new reality.
      
       * The type of `*` is now `*`. No more `BOX`.
      
       * Users can write explicit kind variables in their code,
         anywhere they can write type variables. For backward compatibility,
         automatic inference of kind-variable binding is still permitted.
      
       * The new extension `TypeInType` turns on the new user-facing
         features.
      
       * Type families and synonyms are now promoted to kinds. This causes
         trouble with parsing `*`, leading to the somewhat awkward new
         `HsAppsTy` constructor for `HsType`. This is dispatched with in
         the renamer, where the kind `*` can be told apart from a
         type-level multiplication operator. Without `-XTypeInType` the
         old behavior persists. With `-XTypeInType`, you need to import
         `Data.Kind` to get `*`, also known as `Type`.
      
       * The kind-checking algorithms in TcHsType have been significantly
         rewritten to allow for enhanced kinds.
      
       * The new features are still quite experimental and may be in flux.
      
       * TODO: Several open tickets: #11195, #11196, #11197, #11198, #11203.
      
       * TODO: Update user manual.
      
      Tickets addressed: #9017, #9173, #7961, #10524, #8566, #11142.
      Updates Haddock submodule.
      67465497
  9. 16 Nov, 2015 2 commits
  10. 08 Oct, 2015 1 commit
  11. 21 Sep, 2015 1 commit
    • Edward Z. Yang's avatar
      Unify hsig and hs-boot; add preliminary "hs-boot" merging. · 06d46b1e
      Edward Z. Yang authored
      
      
      This patch drops the file level distinction between hs-boot and hsig;
      we figure out which one we are compiling based on whether or not there
      is a corresponding hs file lying around.
      
      To make the "import A" syntax continue to work for bare hs-boot
      files, we also introduce hs-boot merging, which takes an A.hi-boot
      and converts it to an A.hi when there is no A.hs file in scope.
      This will be generalized in Backpack to merge multiple A.hi files together;
      which means we can jettison the "load multiple interface files" functionality.
      
      This works automatically for --make, but for one-shot compilation
      we need a new mode: ghc --merge-requirements A will generate an A.hi/A.o
      from a local A.hi-boot file; Backpack will extend this mechanism further.
      
      Has Haddock submodule update to deal with change in msHsFilePath behavior.
      
          - This commit drops support for the hsig extension. Can
            we support it?  It's annoying because the finder code is
            written with the assumption that where there's an hs-boot
            file, there's always an hs file too.  To support hsig, you'd
            have to probe two locations.  Easier to just not support it.
      
          - #10333 affects us, modifying an hs-boot still doesn't trigger
            recomp.
      
          - See compiler/main/Finder.hs: this diff is very skeevy, but
            it seems to work.
      
          - This code cunningly doesn't drop hs-boot files from the
            "drop hs-boot files" module graph, if they don't have a
            corresponding hs file.  I have no idea if this actually is useful.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, austin, bgamari, spinda
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1098
      06d46b1e
  12. 05 Aug, 2015 1 commit
    • Simon Peyton Jones's avatar
      Allow proper errors/warnings in core2core passes · e2b57381
      Simon Peyton Jones authored
      This patch makes it possible for core-to-core passes to emit
      proper error messages and warnings.
      
        * New function CoreMonad.warnMsg
      
        * CoreMonad.warnMsg and errorMsg now print a proper warning/error
          message heading.
      
        * CoreMonad carries a SrcSpan, which is used in warning/error
          messages.  It is initialised to be the source file name, but
          a core-to-core pass could set it more specifically if it had
          better location information.
      
      There was a bit of plumbing needed to get the filename to the
      right place.
      e2b57381
  13. 30 Jul, 2015 1 commit
  14. 27 Jul, 2015 1 commit
    • Simon Peyton Jones's avatar
      Improve warnings for rules that might not fire · 2d88a531
      Simon Peyton Jones authored
      Two main things here
      
      * Previously we only warned about the "head" function of the rule,
        but actually the warning applies to any free variable on the LHS.
      
      * We now warn not only when one of these free vars can inline, but
        also if it has an active RULE (c.f. Trac #10528)
      
      See Note [Rules and inlining/other rules] in Desugar
      
      This actually shows up quite a few warnings in the libraries, notably
      in Control.Arrow, where it correctly points out that rules like
          "compose/arr"   forall f g .
                          (arr f) . (arr g) = arr (f . g)
      might never fire, because the rule for 'arr' (dictionary selection)
      might fire first.  I'm not really sure what to do here; there is some
      discussion in Trac #10595.
      
      A minor change is adding BasicTypes.pprRuleName to pretty-print RuleName.
      2d88a531
  15. 22 Jul, 2015 1 commit
  16. 20 Jun, 2015 1 commit
    • Edward Z. Yang's avatar
      Filter orphan rules based on imports, fixes #10294 and #10420. · 0cb1f5cf
      Edward Z. Yang authored
      Summary:
      If we have an orphan rule in our database, don't apply it
      unless the defining module is transitively imported by the
      module we are processing.  We do this by defining a new RuleEnv
      data type which includes both the RuleBase as well as the set
      of visible orphan modules, and threading this through the
      relevant environments (CoreReader, RuleCheckEnv and ScEnv).
      
      This is analogous to the instances fix we applied in #2182
      4c834fdd
      
      , but done for RULES.
      An important knock-on effect is that we can remove some buggy
      code in LoadInterface which tried to avoid loading interfaces
      that were loaded by plugins (which sometimes caused instances
      and rules to NEVER become visible).
      
      One note about tests: I renamed the old plugins07 test to T10420
      and replaced plugins07 with a test to ensure that a plugin
      import did not cause new rules to be loaded in.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate
      
      Reviewers: simonpj, austin, goldfire
      
      Subscribers: bgamari, thomie
      
      Differential Revision: https://phabricator.haskell.org/D950
      
      GHC Trac Issues: #10420
      0cb1f5cf
  17. 01 Jun, 2015 1 commit
    • Alan Zimmerman's avatar
      ApiAnnotations : strings in warnings do not return SourceText · e6191d1c
      Alan Zimmerman authored
      Summary:
      The strings used in a WARNING pragma are captured via
      
          strings :: { Located ([AddAnn],[Located FastString]) }
              : STRING { sL1 $1 ([],[L (gl $1) (getSTRING $1)]) }
          ..
      
      The STRING token has a method getSTRINGs that returns the original
      source text for a string.
      
      A warning of the form
      
          {-# WARNING Logic
                    , mkSolver
                    , mkSimpleSolver
                    , mkSolverForLogic
                    , solverSetParams
                    , solverPush
                    , solverPop
                    , solverReset
                    , solverGetNumScopes
                    , solverAssertCnstr
                    , solverAssertAndTrack
                    , solverCheck
                    , solverCheckAndGetModel
                    , solverGetReasonUnknown
                    "New Z3 API support is still incomplete and fragile: \
                    \you may experience segmentation faults!"
            #-}
      
      returns the concatenated warning string rather than the original source.
      
      This patch now deals with all remaining instances of getSTRING to bring
      in a SourceText for each.
      
      This updates the haddock submodule as well, for the AST change.
      
      Test Plan: ./validate
      
      Reviewers: hvr, austin, goldfire
      
      Reviewed By: austin
      
      Subscribers: bgamari, thomie, mpickering
      
      Differential Revision: https://phabricator.haskell.org/D907
      
      GHC Trac Issues: #10313
      e6191d1c
  18. 12 May, 2015 1 commit
  19. 16 Jan, 2015 1 commit
    • Alan Zimmerman's avatar
      API Annotations tweaks. · 11881ec6
      Alan Zimmerman authored
      Summary:
      HsTyLit now has SourceText
      
      Update documentation of HsSyn to reflect which annotations are attached to which element.
      
      Ensure that the parser always keeps HsSCC and HsTickPragma values, to
      be ignored in the desugar phase if not needed
      
      Bringing in SourceText for pragmas
      
      Add Location in NPlusKPat
      
      Add Location in FunDep
      
      Make RecCon payload Located
      
      Explicitly add AnnVal to RdrName where it is compound
      
      Add Location in IPBind
      
      Add Location to name in IEThingAbs
      
      Add Maybe (Located id,Bool) to Match to track fun_id,infix
        This includes converting Match into a record and adding a note about why
        the fun_id needs to be replicated in the Match.
      
      Add Location in KindedTyVar
      
      Sort out semi-colons for parsing
      
        - import statements
        - stmts
        - decls
        - decls_cls
        - decls_inst
      
      This updates the haddock submodule.
      
      Test Plan: ./validate
      
      Reviewers: hvr, austin, goldfire, simonpj
      
      Reviewed By: simonpj
      
      Subscribers: thomie, carter
      
      Differential Revision: https://phabricator.haskell.org/D538
      11881ec6
  20. 28 Dec, 2014 1 commit
    • Gergő Érdi's avatar
      Support pattern synonyms in GHCi (fixes #9900) · 0cc0cc86
      Gergő Érdi authored
      This involves recognizing lines starting with `"pattern "` as declarations,
      keeping non-exported pattern synonyms in `deSugar`, and including
      pattern synonyms in the result of `hscDeclsWithLocation`.
      0cc0cc86
  21. 16 Dec, 2014 2 commits
    • Peter Wortmann's avatar
      Generalized Coverage pass to allow adding multiple types of Tickishs · 3b893f38
      Peter Wortmann authored
      This allows having, say, HPC ticks, automatic cost centres and source
      notes active at the same time. We especially take care to un-tangle the
      infrastructure involved in generating them.
      
      (From Phabricator D169)
      3b893f38
    • Peter Wortmann's avatar
      Source notes (Core support) · 993975d3
      Peter Wortmann authored
      This patch introduces "SourceNote" tickishs that link Core to the
      source code that generated it. The idea is to retain these source code
      links throughout code transformations so we can eventually relate
      object code all the way back to the original source (which we can,
      say, encode as DWARF information to allow debugging).  We generate
      these SourceNotes like other tickshs in the desugaring phase. The
      activating command line flag is "-g", consistent with the flag other
      compilers use to decide DWARF generation.
      
      Keeping ticks from getting into the way of Core transformations is
      tricky, but doable. The changes in this patch produce identical Core
      in all cases I tested -- which at this point is GHC, all libraries and
      nofib. Also note that this pass creates *lots* of tick nodes, which we
      reduce somewhat by removing duplicated and overlapping source
      ticks. This will still cause significant Tick "clumps" - a possible
      future optimization could be to make Tick carry a list of Tickishs
      instead of one at a time.
      
      (From Phabricator D169)
      993975d3
  22. 15 Dec, 2014 1 commit
    • Simon Peyton Jones's avatar
      Make Core Lint check for locally-bound GlobalIds · d59c59f4
      Simon Peyton Jones authored
      There should be no bindings in this module for a GlobalId;
      except after CoreTidy, when top-level bindings are globalised.
      
      To check for this, I had to make the CoreToDo pass part of the
      environment that Core Lint caries.  But CoreToDo is defined in
      CoreMonad, which (before this patch) called CoreLint.
      
      So I had to do quite a bit of refactoring, moving some
      lint-invoking code into CoreLint itself.  Crucially, I also
      more tcLookupImported_maybe, importDecl, and checkwiredInTyCon
      from TcIface (which use CoreLint) to LoadIface (which doesn't).
      This is probably better structure anyway.
      
      So most of this patch is refactoring. The actual check for
      GlobalIds is in CoreLint.lintAndScopeId
      d59c59f4
  23. 10 Dec, 2014 1 commit
  24. 03 Dec, 2014 1 commit
  25. 21 Nov, 2014 1 commit
  26. 04 Nov, 2014 1 commit
  27. 24 Oct, 2014 1 commit
    • Edward Z. Yang's avatar
      Implementation of hsig (module signatures), per #9252 · aa479953
      Edward Z. Yang authored
      
      
      Summary:
      Module signatures, like hs-boot files, are Haskell modules which omit
      value definitions and contain only signatures.  This patchset implements
      one particular aspect of module signature, namely compiling them against
      a concrete implementation.  It works like this: when we compile an hsig
      file, we must be told (via the -sig-of flag) what module this signature
      is implementing.  The signature is compiled into an interface file which
      reexports precisely the entities mentioned in the signature file.  We also
      verify that the interface is compatible with the implementation.
      
      This feature is useful in a few situations:
      
          1. Like explicit import lists, signatures can be used to reduce
          sensitivity to upstream changes.  However, a signature can be defined
          once and then reused by many modules.
      
          2. Signatures can be used to quickly check if a new upstream version
          is compatible, by typechecking just the signatures and not the actual
          modules.
      
          3. A signature can be used to mediate separate modular development,
          where the signature is used as a placeholder for functionality which
          is loaded in later.  (This is only half useful at the moment, since
          typechecking against signatures without implementations is not implemented
          in this patchset.)
      
      Unlike hs-boot files, hsig files impose no performance overhead.
      
      This patchset punts on the type class instances (and type families) problem:
      instances simply leak from the implementation to the signature.  You can
      explicitly specify what instances you expect to have, and those will be checked,
      but you may get more instances than you asked for.  Our eventual plan is
      to allow hiding instances, but to consider all transitively reachable instances
      when considering overlap and soundness.
      
      ToDo: signature merging: when a module is provided by multiple signatures
      for the same base implementation, we should not consider this ambiguous.
      
      ToDo: at the moment, signatures do not constitute use-sites, so if you
      write a signature for a deprecated function, you won't get a warning
      when you compile the signature.
      
      Future work: The ability to feed in shaping information so that we can take
      advantage of more type equalities than might be immediately evident.
      Signed-off-by: default avatarEdward Z. Yang <ezyang@cs.stanford.edu>
      
      Test Plan: validate and new tests
      
      Reviewers: simonpj, simonmar, hvr, austin
      
      Subscribers: simonmar, relrod, ezyang, carter, goldfire
      
      Differential Revision: https://phabricator.haskell.org/D130
      
      GHC Trac Issues: #9252
      aa479953
  28. 06 Jun, 2014 1 commit
    • Simon Peyton Jones's avatar
      Make the matcher and wrapper Ids in PatSyn into LocalIds, not GlobalIds · 7ac600d5
      Simon Peyton Jones authored
      This was a serious bug, exposed by Trac #9175.  The matcher and wrapper
      must be LocalIds, like record selectors and dictionary functions, for
      the reasons now documented in Note [Exported LocalIds] in Id.lhs
      
      In fixing this I found
       - PatSyn should have an Id inside it (apart from the wrapper and matcher)
         It should be a Name.  Hence psId --> psName, with knock-on consequences
      
       - Tidying of PatSyns in TidyPgm was wrong
      
       - The keep-alive set in Desugar.deSugar (now) doesn't need pattern synonyms
         in it
      
      I also cleaned up the interface to PatSyn a little, so there's a tiny knock-on
      effect in Haddock; hence the haddock submodule update.
      
      It's very hard to make a test for this bug, so I haven't.
      7ac600d5
  29. 15 May, 2014 1 commit
    • Herbert Valerio Riedel's avatar
      Add LANGUAGE pragmas to compiler/ source files · 23892440
      Herbert Valerio Riedel authored
      In some cases, the layout of the LANGUAGE/OPTIONS_GHC lines has been
      reorganized, while following the convention, to
      
      - place `{-# LANGUAGE #-}` pragmas at the top of the source file, before
        any `{-# OPTIONS_GHC #-}`-lines.
      
      - Moreover, if the list of language extensions fit into a single
        `{-# LANGUAGE ... -#}`-line (shorter than 80 characters), keep it on one
        line. Otherwise split into `{-# LANGUAGE ... -#}`-lines for each
        individual language extension. In both cases, try to keep the
        enumeration alphabetically ordered.
        (The latter layout is preferable as it's more diff-friendly)
      
      While at it, this also replaces obsolete `{-# OPTIONS ... #-}` pragma
      occurences by `{-# OPTIONS_GHC ... #-}` pragmas.
      23892440
  30. 11 Feb, 2014 1 commit
  31. 20 Jan, 2014 1 commit
    • Gergő Érdi's avatar
      Implement pattern synonyms · 4f8369bf
      Gergő Érdi authored
      This patch implements Pattern Synonyms (enabled by -XPatternSynonyms),
      allowing y ou to assign names to a pattern and abstract over it.
      
      The rundown is this:
      
        * Named patterns are introduced by the new 'pattern' keyword, and can
          be either *unidirectional* or *bidirectional*. A unidirectional
          pattern is, in the simplest sense, simply an 'alias' for a pattern,
          where the LHS may mention variables to occur in the RHS. A
          bidirectional pattern synonym occurs when a pattern may also be used
          in expression context.
      
        * Unidirectional patterns are declared like thus:
      
              pattern P x <- x:_
      
          The synonym 'P' may only occur in a pattern context:
      
              foo :: [Int] -> Maybe Int
              foo (P x) = Just x
              foo _     = Nothing
      
        * Bidirectional patterns are declared like thus:
      
              pattern P x y = [x, y]
      
          Here, P may not only occur as a pattern, but also as an expression
          when given values for 'x' and 'y', i.e.
      
              bar :: Int -> [Int]
              bar x = P x 10
      
        * Patterns can't yet have their own type signatures; signatures are inferred.
      
        * Pattern synonyms may not be recursive, c.f. type synonyms.
      
        * Pattern synonyms are also exported/imported using the 'pattern'
          keyword in an import/export decl, i.e.
      
              module Foo (pattern Bar) where ...
      
          Note that pattern synonyms share the namespace of constructors, so
          this disambiguation is required as a there may also be a 'Bar'
          type in scope as well as the 'Bar' pattern.
      
        * The semantics of a pattern synonym differ slightly from a typical
          pattern: when using a synonym, the pattern itself is matched,
          followed by all the arguments. This means that the strictness
          differs slightly:
      
              pattern P x y <- [x, y]
      
              f (P True True) = True
              f _             = False
      
              g [True, True] = True
              g _            = False
      
          In the example, while `g (False:undefined)` evaluates to False,
          `f (False:undefined)` results in undefined as both `x` and `y`
          arguments are matched to `True`.
      
      For more information, see the wiki:
      
          https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms
          https://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms/Implementation
      
      Reviewed-by: default avatarSimon Peyton Jones <simonpj@microsoft.com>
      Signed-off-by: default avatarAustin Seipp <austin@well-typed.com>
      4f8369bf
  32. 09 Jan, 2014 1 commit
    • Simon Peyton Jones's avatar
      Re-work the naming story for the GHCi prompt (Trac #8649) · 73c08ab1
      Simon Peyton Jones authored
      The basic idea here is simple, and described in Note [The interactive package]
      in HscTypes, which starts thus:
      
          Note [The interactive package]
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
          Type and class declarations at the command prompt are treated as if
          they were defined in modules
             interactive:Ghci1
             interactive:Ghci2
             ...etc...
          with each bunch of declarations using a new module, all sharing a
          common package 'interactive' (see Module.interactivePackageId, and
          PrelNames.mkInteractiveModule).
      
          This scheme deals well with shadowing.  For example:
      
             ghci> data T = A
             ghci> data T = B
             ghci> :i A
             data Ghci1.T = A  -- Defined at <interactive>:2:10
      
          Here we must display info about constructor A, but its type T has been
          shadowed by the second declaration.  But it has a respectable
          qualified name (Ghci1.T), and its source location says where it was
          defined.
      
          So the main invariant continues to hold, that in any session an original
          name M.T only refers to oe unique thing.  (In a previous iteration both
          the T's above were called :Interactive.T, albeit with different uniques,
          which gave rise to all sorts of trouble.)
      
      This scheme deals nicely with the original problem.  It allows us to
      eliminate a couple of grotseque hacks
        - Note [Outputable Orig RdrName] in HscTypes
        - Note [interactive name cache] in IfaceEnv
      (both these comments have gone, because the hacks they describe are no
      longer necessary). I was also able to simplify Outputable.QueryQualifyName,
      so that it takes a Module/OccName as args rather than a Name.
      
      However, matters are never simple, and this change took me an
      unreasonably long time to get right.  There are some details in
      Note [The interactive package] in HscTypes.
      73c08ab1
  33. 28 Nov, 2013 1 commit
    • Simon Peyton Jones's avatar
      More faff to get GHCi's top-level environment right · f3a84161
      Simon Peyton Jones authored
      This fixes #8540 (again), and simplifies matters a bit more. In
      particular, I got rid of ic_sys_vars altogether.  Mostly they can just
      go in ic_tythings, apart from dfuns, which are readily gettable from
      the instances anyway.
      
      See documentation in Note [Initialising the type environment for GHCi]
      in TcEnv.
      f3a84161
  34. 22 Nov, 2013 1 commit
  35. 23 Oct, 2013 1 commit
  36. 03 Sep, 2013 1 commit
    • Simon Peyton Jones's avatar
      Improve Linting in GHCi (fixes Trac #8215) · dfa8ef03
      Simon Peyton Jones authored
      The original problem was that we weren't bringing varaibles bound in the
      interactive context into scope before Linting the result of a top-level
      declaration in GHCi.  (We were doing this for expressions.)
      
      Moreover I found that we weren't Linting the result of desugaring
      a GHCi expression, which we really should be doing.
      
      It took me a bit of time to unravel all this, and I did some refactoring
      to make it easier next time.
      
        * CoreMonad contains the Lint wrappers that get the right
          environments into place.  It always had endPass and lintPassResult
          (which Lints bindings), but now it has lintInteractiveExpr.
      
        * Both use a common function CoreMonad.interactiveInScope to find
          those in-scope variables.
      
      Quite a bit of knock-on effects from this, but nothing exciting.
      dfa8ef03
  37. 28 Jul, 2013 1 commit
  38. 25 Jul, 2013 1 commit