Oh, also my complete pipeline is here:
https://github.com/chrisdone/prana/blob/0cbb7b4b96bbfdb4f0d6a60e08f4b1f53abd...
Parse/typecheck/desugar, tidy, prep, core-to-stg (ripped from HscMain) and
then I try to resolve all names in the AST and that leads me to this.
On Sat, 30 Mar 2019 at 14:05, Christopher Done
Hi all,
Could you offer some insight into newtypes at the STG level? Here’s the context:
1.
I’m working on this interpreter for STG (https://github.com/chrisdone/prana) and I’m trying to generate a pristine AST where all names in it are resolved to something known to me. 2.
I’ve compiled ghc-prim and integer-gmp without issue, and I’m compiling base and there remains one last frontier which is newtypes.
These are the culprits pointed out if I compile base:
chris@precision:~/Work/chrisdone/prana/ghc-8.4/libraries/base-4.11.1.0$ PRANA_INDEX=../prana.idx stack build --exec './Setup build --ghc-options=-O0' --file-watch Preprocessing library for base-4.11.1.0.. Building library for base-4.11.1.0.. [1 of 244] Compiling GHC.Base [2 of 244] Compiling GHC.IO [3 of 244] Compiling GHC.Real [4 of 244] Compiling Data.Semigroup.Internal ... [snip] ... [242 of 244] Compiling Data.Functor.Compose [243 of 244] Compiling Data.Fixed [244 of 244] Compiling Data.Complex
Errors in Data.Foldable: Variable name not found: base:Data.Semigroup.Internal.All Variable name not found: base:Data.Semigroup.Internal.Any
Errors in Foreign.Marshal.Pool: Variable name not found: base:Foreign.Marshal.Pool.Pool
Errors in GHC.ExecutionStack.Internal: Variable name not found: base:GHC.ExecutionStack.Internal.StackTrace
Errors in Data.Bifoldable: Variable name not found: base:Data.Semigroup.Internal.All Variable name not found: base:Data.Semigroup.Internal.Any
Errors in System.Timeout: Variable name not found: base:System.Timeout.Timeout
Errors in Data.Data: Variable name not found: base:Foreign.Ptr.WordPtr Variable name not found: base:Foreign.Ptr.IntPtr Variable name not found: base:Data.Semigroup.Internal.Any Variable name not found: base:Data.Semigroup.Internal.All
I looked these up, and they all appear to be *uses* of a newtype.
For example, in the Timeout function:
http://hackage.haskell.org/package/base-4.12.0.0/docs/src/System.Timeout.htm...
I printed out the full [StgTopBinding] list and got:
let { sat_s27NC [Occ=Once] :: IO Timeout [LclId] = [] \u [] fmap $fFunctorIO Timeout newUnique; } in >>= $fMonadIO sat_s27NC sat_s27NT;
Oddly (or not?), they’re used as values, not constructors. This error comes from this part of my code:
StgSyn.StgApp occ arguments -> AppExpr <$> lookupSomeVarId occ <*> traverse fromStgGenArg arguments
If it was used as a constructor, it’d appear in this position, where looking up the ID would produce a “Data constructor name not found” error:
StgSyn.StgConApp dataCon arguments types -> ConAppExpr <$> lookupDataConId dataCon <*> traverse fromStgGenArg arguments <*> pure (map (const Type) types)
My understanding of newtypes at this stage is hazy. It seems like:
-
They ought to be erased and replaced with coercions by now. If they’re not replaced, it’s because they’re in a not-quite-id position like fmap Timeout .... (Arguably these could be fixed in base with a Data.Coerce.coerce?) -
However, the CoreTidy/PrepPgm processing modules don’t seem to have removed or replaced these, or introduced a binding that would do something.
At this stage what would you recommend? At this point type-checking is done, and I only care about interpreting the code. So I suppose they could be id for all it matters to the interpreter?
I imagine they aren’t actually supposed to allocate something here. And I’m certain that any pattern matching on a newtype is also erased away by this point.
Cheers!
Chris