• Thomas Schilling's avatar
    Major clean-up of HscMain. · e06951a7
    Thomas Schilling authored
    This patch entails a major restructuring of HscMain and a small bugfix
    to MkIface (which required the restructuring in HscMain).
    
    In MkIface:
    
      - mkIface* no longer outputs orphan warnings directly and also no
        longer quits GHC when -Werror is set.  Instead, errors are
        reported using the common IO (Messages, Maybe result) scheme.
    
    In HscMain:
    
      - Get rid of the 'Comp' monad.  This monad was mostly GhcMonad + two
        reader arguments, a ModSummary for the currently compiled module
        and a possible old interface.  The latter actually lead to a small
        space-leak since only its hash was needed (to check whether the
        newly-generated interface file was the same as the original one).
    
        Functions originally of type 'Comp' now only take the arguments
        that they actually need.  This leads to slighly longer argument
        lists in some places, however, it is now much easier to see what
        is actually going on.
    
      - Get rid of 'myParseModule'.  Rename 'parseFile' to 'hscParse'.
    
      - Join 'deSugarModule' and 'hscDesugar' (keeping the latter).
    
      - Rename 'typecheck{Rename}Module{'}' to 'hscTypecheck{Rename}'.
        One variant keeps the renamed syntax, the other doesn't.
    
      - Parameterise 'HscStatus', so that 'InteractiveStatus' is just a
        different parameterisation of 'HscStatus'.
    
      - 'hscCompile{OneShot,Batch,Nothing,Interactive}' are now
        implemented using a (local) typeclass called 'HsCompiler'.  The
        idea is to make the common structure more obvious.  Using this
        typeclass we now have two functions 'genericHscCompile' (original
        'hscCompiler') and 'genericHscRecompile' (original 'genComp')
        describing the default pipeline.  The methods of the typeclass
        describe a sort of "hook" interface (in OO-terms this would be
        called the "template method" pattern).
    
        One problem with this approach is that we parameterise over the
        /result/ type which, in fact, is not actually different for
        "nothing" and "batch" mode.  To avoid functional dependencies or
        associated types, we use type tags to make them artificially
        different and parameterise the type class over the result type.
        A perhaps better approach might be to use records instead.
        
      - Drop some redundant 'HscEnv' arguments.  These were likely
        different from what 'getSession' would return because during
        compilation we temporarily set the module's DynFlags as well as a
        few other fields.  We now use the 'withTempSession' combinator to
        temporarily change the 'HscEnv' and automatically restore the
        original session after the enclosed action has returned (even in
        case of exceptions).
    
      - Rename 'hscCompile' to 'hscGenHardCode' (since that is what it
        does).
    
    Calls in 'GHC' and 'DriverPipeline' accordingly needed small
    adaptions.
    e06951a7
HscTypes.lhs 79.1 KB