Extract error code from message

ale_linters/solidity/solhint.vim

@@ -5,7 +5,7 @@ function! ale_linters#solidity#solhint#Handle(buffer, lines) abort
     " Matches patterns like the following:
     " /path/to/file/file.sol: line 1, col 10, Error - 'addOne' is defined but never used. (no-unused-vars)
 
-    let l:pattern = '\v^[^:]+: line (\d+), col (\d+), (Error|Warning) - (.*)$'
+    let l:pattern = '\v^[^:]+: line (\d+), col (\d+), (Error|Warning) - (.*) \((.*)\)$'
     let l:output = []
 
     for l:match in ale#util#GetMatches(a:lines, l:pattern)
@@ -14,7 +14,8 @@ function! ale_linters#solidity#solhint#Handle(buffer, lines) abort
         \   'lnum': l:match[1] + 0,
         \   'col': l:match[2] + 0,
         \   'text': l:match[4],
-        \   'type': l:isError ? 'E' : 'W'
+        \   'code': l:match[5],
+        \   'type': l:isError ? 'E' : 'W',
         \})
     endfor