wiki:Status/SLPJ-Tickets

Version 210 (modified by simonpj, 2 years ago) (diff)

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This page collects tickets that Simon PJ is interested in, so that he remembers them

New typechecker things to fix (with Dimitrios)

  • #5321: slow constraint solving
  • #4347: rigid type signatures for impredicativity
  • #4310, #5595: deferred equalities and forall types (needs Brent's work)
  • #5320: overlap delicacy

Arity

  • #3924: weak arity leads to weak strictness
  • #3698: arity analysis again
  • #3697: class method selectors
  • #3034: divInt and arity
  • #3627: profiling and eta expansion
  • #2915: arity too small
  • #2823: another arity expansion bug (related to dictionaries)
  • #2440: bad code with type families; I believe this is also arity-related
  • #1547: profiling and arity

Inlining

  • #3872, #5400, #5448, #5722: contravariant data type loop in simplifier inliner
  • #4833: finding the right loop breaker
  • #3781, #3755: inlining for local functions: discount for scrutinising free vars
  • #3765: CONLIKE things and case expressions (need two unfoldings)
  • #3073 and Commentary/Compiler/DesugaringInstances: better desugaring for instances
  • #2396: default class method not inlined
  • #2078: INLINing improvement; ask Christian.Maeder@… to see if it improves CASL
  • #2840: top level unlifted string literals
  • #3123: feature request: recursive inlining and peeling

New code generator

  • Summary ticket: #4258, and wiki page
  • #4065: forward propagation
  • #3132: fix cgCase of PrimAlts
  • #3458, #1216: undesirable allocation of something that is nearly a let-no-escape
  • #3462: allocate large objects with allocateLocal()
  • #2253: NCG could do better. Look at this when John D’s ncg is working
  • #783: SRTs getting big
  • #2289: cheap check at start of case alternatives
  • #2731: avoiding unnecessary evaluation when unpacking constructors
  • #3940: propagate fix

Optimiser

  • #5262: seq magic
  • #605: strict/unboxed enumerations
  • #2607: space leak: inlining defeats selector thunk optimisation
  • #4470: merge identical counters
  • #2439: Strict dictionaries
  • #3138: returning a known constructor (Lennart's cmonad package)
  • #2988: better float-in
  • #2940: do CSE after CorePrep
  • #2132: Optimise nested comparisons: if you know x>0 then you know x>=1 etc. Maybe a special pass that knows about arithmetic?
  • #149: float-out/CSE
  • #2289, #2387, #1600: nested CPR analysis
  • #2255, #3767, #2642, #3831, #4941: Improve SpecConstr for free variables, and for join points.
  • #2374: SAT and MutableByteArray Max?
  • #5363: profiling worsens space behaviour

Compiler performance

  • #2346: desugaring let-bindings
  • Use wildcards for dead variables in interface files.

Tiresome arithmetic things

  • #5237: x squared is too slow
  • #2281: properFraction implemented with modf primitive?
  • #4101: constant folding for (**)
  • #3676: realToFrac conversions
  • #3744: comparisons against minBound and maxBound are not optimised away
  • #3065: quot is sub-optimal
  • #2269: Word type to Double or Float conversions

GHCi

  • #4017: unhelpful GHCi message


Outright bugs

  • #2182: GHCi session retains instance after removing a module from scope
  • #1241: Lifting the Coverage Condition for functional dependencies isn’t the Right Thing Manuel

New constraint simplifier

Types and type inference

  • #5224: make it cheaper to check for inconsistent type family instances
  • #4466, #5296: explicit type application
  • #3714: distinguish type parameters from indices
  • #4259: overlapping type family instances
  • #3490: superclasses and ambiguity
  • #3632: better update for records with existentials
  • #1496, #4846: Newtype deriving and type families type soundness problem
  • #1897: Ambiguity: don't infer a type that can't be checked if the type is given as a signature (this one is important). See SPJ's mailbox: Haskell type system/Ambiguity.
  • #2641: revise what -XExtendedDefaultRules does
  • #3592: deep skolemisation
  • #2357: Implement the Haskell Prime proposal for polymorphic pattern bindings

Better error messages

  • #4921: ambiguous type variables
  • #1330: another bad error message (Church2)
  • #2648: Report out of date interface files robustly
  • #2588: Better error message about ‘forall’
  • #2360: Better location info in occurs-check message.
  • #1928: Confusing type error message (Claus makes suggestions)
  • #2534: Another confusing type error message
  • #2900: Improve decomposition of function types

Template Haskell

Features

  • #5630: External core needs love
  • #5429: docase and joinads
  • #5391: better deriving Typeable
  • #5248: Infer context in type signatures
  • #5144: pattern synonyms
  • #5073: blockST and friends
  • #788, #2895: Class aliases
  • #2595: record updates
  • #4823: strength reduction for array indexing
  • #4479: type directed name resolution (TDNR)
  • #4426: simpler rule for implicit quantification
  • #4372: better quasiquotes
  • #4359: lambda case
  • #4148: improvements to mdo syntax
  • #595: pattern-match overlap checking
  • #3843: Add plugins
  • #3701: Implicitly declared existentials: a class as a type
  • #3217: better flag handling for GHCi
  • #2600, #2110: Bind type variables and constraints in RULES
  • #1930: Infix type operators: a+b.
  • #960: Generate local info for ‘undefined’. Implicit location parameters in general
  • #2135: Warn when exporting a function whose type mentions a type constructor defined locally but not itself exported
  • #2526: Add -fwarn-missing-export-signatures
  • #2119: Explicitly importing deprecated symbols should generate deprecation warnings
  • #2207: Load interfaces for GHC.* even without -O
  • #1231: Better deprecations

Not sure what to do about these

  • #2284: the state-hack "optimisation" causes much re-computation
  • #4005: generational GC pathalogical case
  • #1349: strict function argument types