Skip to content

ghci with ":set +t" should print type before starting evaluation

Not an actual bug, but questionable design perhaps.

I think this is backwards, as static analysis comes before evaluation, not after:

Prelude> :set +t
Prelude> reverse [True]
[True]
it :: [Bool]

When evaluation raises an exception, no type is printed.

Prelude> :set +t
Prelude> True && undefined
*** Exception: Prelude.undefined
CallStack (from HasCallStack):
  error, called at libraries/base/GHC/Err.hs:79:14 in base:GHC.Err
  undefined, called at <interactive>:8:9 in interactive:Ghci4

For teaching (and for my own sanity) I'd much prefer output in logical succession.

Trac metadata
Trac field Value
Version
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component GHCi
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information