Add native build and compiler driver

src/diagnostic.ml

@@ -0,0 +1,58 @@
+type t = {
+  file : string;
+  span : Location.span;
+  message : string;
+}
+
+exception Error of t
+
+let current_file = ref ""
+
+let set_file file = current_file := file
+
+let file_label () = if !current_file = "" then "<none>" else !current_file
+
+let file () = file_label ()
+
+let error span fmt =
+  Printf.ksprintf
+    (fun message -> raise (Error { file = file_label (); span = span; message = message }))
+    fmt
+
+let make span message = { file = file_label (); span = span; message = message }
+
+let header d =
+  if Location.is_none d.span then Printf.sprintf "%s: error: %s" d.file d.message
+  else Printf.sprintf "%s:%d:%d: error: %s" d.file d.span.Location.start.Location.line
+      d.span.Location.start.Location.col d.message
+
+let to_string d = header d
+
+let source_line text line =
+  if line <= 0 then None
+  else
+    let lines = String.split_on_char '\n' text in
+    let rec nth items index =
+      match items with
+      | [] -> None
+      | head :: tail -> if index = 1 then Some head else nth tail (index - 1)
+    in
+    nth lines line
+
+let render source d =
+  let head = header d in
+  match source with
+  | None -> head
+  | Some text -> (
+      match source_line text d.span.Location.start.Location.line with
+      | None -> head
+      | Some line ->
+          let col = max 1 d.span.Location.start.Location.col in
+          let width =
+            if d.span.Location.stop.Location.line = d.span.Location.start.Location.line then
+              max 1 (d.span.Location.stop.Location.col - col)
+            else max 1 (String.length line - col + 1)
+          in
+          let padding = String.make (col - 1) ' ' in
+          let carets = String.make width '^' in
+          Printf.sprintf "%s\n  %s\n  %s%s" head line padding carets)