digitallyinduced/ihp

`Could not deduce (IsString string0)` when using logger (from v0.10.0 onwards)

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#927 opened on Jun 20, 2021

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Description

Upon upgrading from 0.9.0 to 0.10.0 I get an error on this:

Log.debug "Some log message"

The error:

    • Could not deduce (IsString string0)
        arising from the literal '"Some log message"'
...
      The type variable 'string0' is ambiguous
      These potential instances exist:
        instance IsString Value
          -- Defined in 'aeson-1.5.4.1:Data.Aeson.Types.Internal'
        instance IsString ByteString
          -- Defined in 'Data.ByteString.Internal'
        instance (a ~ Char) => IsString (Seq a)
          -- Defined in 'Data.Sequence.Internal'
        ...plus four others
        ...plus 37 instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)

Doing this works:

Log.debug ("Some log message" :: Text)

But that's a bit annoying to do everywhere. Anything smart I can do with my imports or something to avoid having to do that? Or must I be doing something weird to get this error in the first place?

Ref https://ihpframework.slack.com/archives/C01DQE0F4F8/p1624128600130600

Contributor guide

Research direction
Investigate the type signature of `IHP.Log.debug` and how it changed between versions 0.9.0 and 0.10.0. Check if it now requires `OverloadedStrings` or if the type variable `message` is too polymorphic. Look at the commit that introduced the change and see if adding a type constraint like `(IsString message, Loggable message)` resolves the issue. Also check the IHP documentation for proper usage.
Tech stack
None
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
HaskellOverloadedStrings extension
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40