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  • #11573

Closed
Open
Opened Feb 13, 2016 by Ben Gamari@bgamari🐢Maintainer

Inferred CallStacks expose implicit parameter

It was noticed (in a thread on ghc-devs) that introducing a CallStack-carrying term into the RHS of a let binding in GHCi produces a type which itself carries a callstack.

I could be wrong but as far as I know this is a bug: the solver should never introduce a constraint that the user didn't write; it should merely provide an empty callstack in the event that a callstack constraint can't be solved.

Prelude> let myList = [1, 2, 3 :: Integer]
Prelude> let myList' = myList ++ undefined
Prelude> :t myList
myList :: [Integer]
Prelude> :t myList'
myList' :: (?callStack::GHC.Stack.Types.CallStack) => [Integer]
Trac metadata
Trac field Value
Version 8.0.1-rc2
Type Bug
TypeOfFailure OtherFailure
Priority high
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC gridaphobe
Operating system
Architecture
Edited Mar 10, 2019 by Eric Seidel
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Assign to
8.0.1
Milestone
8.0.1 (Past due)
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Reference: ghc/ghc#11573