Use fourmolu as Haskell formatter and fixer

lua/confformat.lua

@@ -43,6 +43,20 @@ require("formatter").setup({
 			require("formatter.filetypes.rust").rustfmt,
 		},
 
+		haskell = {
+			function()
+				-- Full specification of configurations is down below and in Vim help
+				-- files
+				return {
+					exe = "fourmolu",
+					args = {
+						util.escape_path(util.get_current_buffer_file_path()),
+					},
+					stdin = true,
+				}
+			end,
+		},
+
 		-- Use the special "*" filetype for defining formatter configurations on
 		-- any filetype
 		["*"] = {

lua/linterconfiguration.lua

@@ -24,6 +24,7 @@ vim.g.ale_fixers = {
 	markdown = { "prettier", "pandoc" },
 	python = { "yapf" },
 	pascal = { "ptop" },
+	haskell = { "fourmolu" },
 }
 
 vim.keymap.set("n", "<leader>lf", ":ALEFix<CR>")