Explanation of a core-lint warning (Bad getNth)

[Thomas Miedema]

On Fri, Jan 15, 2016 at 3:03 PM, Jan Bracker <jan.bracker at googlemail.com>
wrote:

> You just have to download the three files and run "cabal install" to
> reproduce the error.
>

It's never that easy, is it? Can you try in a cabal sandbox, with
ghc-7.10.3. I'm getting:



cabal: Could not resolve dependencies:
trying: core-error-0.1 (user goal)
next goal: base (dependency of core-error-0.1)
rejecting: base-4.8.2.0/installed-0d6... (conflict: core-error =>
base==4.8.1.0)
rejecting: base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1,
base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0,
base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2,
base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2,
base-3.0.3.1 (constraint from main config /home/thomas/.cabal/config
requires
installed instance)
Dependency tree exhaustively searched.



After relaxing the depenency on base (or is the problem only reproducible
with base 4.8.1.0 that, in case we are done here), I get:





Preprocessing library effect-monad-0.6.1...

src/Control/Effect/State.hs:4:14: Warning:
    -XOverlappingInstances is deprecated: instead use per-instance pragmas
OVERLAPPING/OVERLAPPABLE/OVERLAPS
[ 1 of 17] Compiling Control.Effect.Helpers.List (
src/Control/Effect/Helpers/List.hs,
dist/build/Control/Effect/Helpers/List.o )
[ 2 of 17] Compiling Control.Effect.Cond ( src/Control/Effect/Cond.hs,
dist/build/Control/Effect/Cond.o )
[ 3 of 17] Compiling Control.Effect   ( src/Control/Effect.hs,
dist/build/Control/Effect.o )
[ 4 of 17] Compiling Control.Effect.Counter (
src/Control/Effect/Counter.hs, dist/build/Control/Effect/Counter.o )
[ 5 of 17] Compiling Control.Effect.CounterNat (
src/Control/Effect/CounterNat.hs, dist/build/Control/Effect/CounterNat.o )
[ 6 of 17] Compiling Control.Effect.Maybe ( src/Control/Effect/Maybe.hs,
dist/build/Control/Effect/Maybe.o )
[ 7 of 17] Compiling Control.Effect.Monad ( src/Control/Effect/Monad.hs,
dist/build/Control/Effect/Monad.o )
[ 8 of 17] Compiling Control.Effect.Parameterised (
src/Control/Effect/Parameterised.hs,
dist/build/Control/Effect/Parameterised.o )
[ 9 of 17] Compiling Control.Effect.Reader ( src/Control/Effect/Reader.hs,
dist/build/Control/Effect/Reader.o )

src/Control/Effect/Reader.hs:33:8:
    Not in scope: type constructor or class ‘Var’

src/Control/Effect/Reader.hs:33:28:
    Not in scope: type constructor or class ‘:->’

src/Control/Effect/Reader.hs:34:5:
    Not in scope: data constructor ‘Var’

src/Control/Effect/Reader.hs:34:24:
    Not in scope: data constructor ‘Var’

src/Control/Effect/Reader.hs:34:28:
    Not in scope: data constructor ‘:->’
Failed to install effect-monad-0.6.1
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