Add support for gleam, closes #655

Co-authored-by: Jeff Kreeftmeijer <jeffkreeftmeijer@gmail.com>

compiler/gleam.vim

@@ -0,0 +1,49 @@
+if has_key(g:polyglot_is_disabled, 'gleam')
+  finish
+endif
+
+" Check we've not run already
+if exists('current_compiler')
+    finish
+endif
+
+let current_compiler = "gleam"
+
+" Defined CompilerSet command if it doesn't exist.
+" Needed for older vim versions.
+if exists(":CompilerSet") != 2
+  command -nargs=* CompilerSet setlocal <args>
+endif
+
+" Tell vim to run 'gleam' when the user runs :make. So ':make build .' becomes
+" 'gleam build .'
+CompilerSet makeprg=gleam\ $*
+
+
+" With the compiler set, we set the errorformat which is a set of rules that
+" vim uses to parse the output of the current compiler program in order to
+" extract file, line, column & error message information so that it can
+" populate the quickfix list and the user can jump between the errors.
+"
+" This errorformat 'parser' will have to change if the output of the compiler
+" changes.
+"
+" Written with the help of: https://flukus.github.io/vim-errorformat-demystified.html
+"
+CompilerSet errorformat=%Eerror:\ %m                  " use 'error:' to indicate the start of a new error
+CompilerSet errorformat+=%C\ %#┌─%#\ %f:%l:%c\ %#-%#  " pull out the file, line & column (matches optional spaces & dashes at the end in case they come back.)
+CompilerSet errorformat+=%C                           " allow empty lines within an error
+CompilerSet errorformat+=%C%.%#│%.%#                  " ignore any line with a vertial formatting pipe in it
+CompilerSet errorformat+=%Z%m                         " assume any other line contributes to the error message
+
+
+" Example error message
+"
+" error: Unknown variable
+"    ┌─ /home/michael/root/projects/tutorials/gleam/try/code/src/main.gleam:19:18
+"    │
+" 19 │   Ok(tuple(name, spot))
+"    │                  ^^^^ did you mean `sport`?
+" 
+" The name `spot` is not in scope here.
+