No instance for ‘Data.Default.Class.Default Conn.TLSSettings’

[danwdart]

Attempting to build smtp-mail 0.5.0.0 gives me:

Building library for smtp-mail-0.5.0.0...
[1 of 3] Compiling Network.Mail.SMTP.Auth ( Network/Mail/SMTP/Auth.hs, dist/build/Network/Mail/SMTP/Auth.o, dist/build/Network/Mail/SMTP/Auth.dyn_o )
[2 of 3] Compiling Network.Mail.SMTP.Types ( Network/Mail/SMTP/Types.hs, dist/build/Network/Mail/SMTP/Types.o, dist/build/Network/Mail/SMTP/Types.dyn_o )
[3 of 3] Compiling Network.Mail.SMTP ( Network/Mail/SMTP.hs, dist/build/Network/Mail/SMTP.o, dist/build/Network/Mail/SMTP.dyn_o )
Network/Mail/SMTP.hs:100:23: error: [GHC-39999]
    • No instance for ‘Data.Default.Class.Default Conn.TLSSettings’
        arising from a use of ‘def’
    • In the expression: def
      In an equation for ‘defaultTlsSettings’: defaultTlsSettings = def
    |
100 | defaultTlsSettings =  def
    |                       ^^^

Error: [Cabal-7125]

Perhaps it's the version of data-default or something?

Cheers

[danwdart]

Hmm, adding allow-newer: data-default-class to my package does let me bypass this issue.

[Bodigrim]

The issue is caused by a major refactoring of data-default / data-default-class. Going forwards, packages are better to depend on data-default only, because data-default-class is not a compatibility shim.

That said, @danwdart could you figure out which version of tls package is used by your build without allow-newer? Something like cabal --store-dir $(mktemp -d) build --dry-run | grep tls.