Fix suggestAddTypeAnnotation regex

[kderme]

I had a code with some warnings

module Main where

main :: IO ()
main =
    let x = 3
    in return ()

The suggestion is

2020-12-30 06:33:26.391800777 [ThreadId 7] - <--2--{"result":[{"edit":{"changes":{"file:///home/kostas/programming/test-
hls/Main.hs":[{"range":{"start":{"line":4,"character":12},"end":{"line":4,"character":13}},"newText":"(3’ • In the expression: 3 In 
an equation for ‘x :: Integer)"}]}},"kind":"quickfix","diagnostics":[{"severity":2,"range":{"start":{"line":4,"character":12},"end":
{"line":4,"character":13}},"source":"typecheck","message":"• Defaulting the following constraint to type ‘Integer’\n    Num p0 
arising from the literal ‘3’\n• In the expression: 3\n  In an equation for ‘x’: x = 3\n  In the expression: let x = 3 in return 
()"}],"title":"Add type annotation ‘Integer’ to ‘3’ • In the expression: 3 In an equation for ‘x’"}],"jsonrpc":"2.0","id":556}

and it results in a wrong fix:

- let x = 3
+ let x = (3’ • In the expression: 3 In an equation for ‘x :: Integer)

From the warning

    - Defaulting the following constraint to type ‘Integer’
        Num p0 arising from the literal ‘3’
    - In the expression: 3
      In an equation for ‘x’: x = 3
      In the expression: let x = 3 in return ()

it seems the lit is parsed as 3’ • In the expression: 3 In an equation for ‘x instead of 3 since it is longer and still valid:

• It is wrapped in ' '
• There is a second In the expression after it.

Btw the approach here seems rather hacky. Are there any plans for ghc to give better support for fix sugestions?

tested with ghc-8.8.4

[pepeiborra]

There are plans to make GHC produce structured errors: https://gitlab.haskell.org/ghc/ghc/-/issues/18516

[pepeiborra]

How do we know that your fix works? A new test case in https://github.com/haskell/haskell-language-server/blob/master/ghcide/test/exe/Main.hs would be great.

[pepeiborra]

Awesome, thanks!