Orphan instances detection in haskell-process-trigger-suggestions is outdated

[geraldus]

I can't be certain, but it looks like orphan instance warning have changed in recent versions of GHC. Currently haskell-process-trigger-suggestions function uses following regex to detect orphan instance warnings in compiler response "Warning: orphan instance: " [1], while GHC 7.10.3 gives a bit different formatting:

/Users/oman/dev/haskell/sol/solitaire/src/Solitaire.hs:12:10: Warning:
    Orphan instance: instance Show Layer
    To avoid this
        move the instance declaration to the module of the class or of the type, or
        wrap the type with a newtype and declare the instance on the new type.

As a result, haskell-process-trigger-suggestions does not suggest to add OPTIONS pragma as intended.

@gracjan I know we need tests for this function, it's quite big and good test suite should rely on genuine GHC response, what will you say?

[geraldus]

TODO test other suggestions:

• Use … to permit this (example file created)
• Use … to allow (example file created)
• Use … if you want to disable this (example file created)
• use …
• You need
• against inferred type [Char] (can't find such string in GHC 8 sources)
• with actual type [Char] (can't find such string in GHC 8 sources)
• haskell-process-suggest-google-imports
• haskell-process-suggest-haskell-docs-import
• haskell-process-suggest-hayoo-imports
• haskell-process-suggest-add-package

[geraldus]

It looks like orphan instances warning was changed really long ago: ghc/ghc@5508ada#diff-e8ff0f7ff4e9411e2df0dba1dbd4bdd8L846

[gracjan]

We should have a test file per each warning message. Then we should run each supported GHC version with each file producing a matrix of NxM messages.

And then we need to support all of that :)

[gracjan]

@geraldus: Can you do first step, that is generate X.hs files, each generating one message of interest?

[geraldus]

@gracjan Maybe at the of week, but no promises.

[geraldus]

@gracjan I have created few files, but have no idea what to do with them :D

[gracjan]

We need a test case. Can you put them in a directory under tests and then create a pull request? We will make something sensible with this.

[geraldus]

Done #1168