Parse scalar expressions with source spans

src/parse.ml

@@ -0,0 +1,17 @@
+let one_line text =
+  match String.index_opt text '\n' with
+  | Some index -> String.sub text 0 index
+  | None -> text
+
+let unexpected text lexbuf =
+  let start = Lexing.lexeme_start_p lexbuf in
+  let stop = Lexing.lexeme_end_p lexbuf in
+  let token =
+    if start.Lexing.pos_cnum >= String.length text then "end of file"
+    else "`" ^ one_line (Lexing.lexeme lexbuf) ^ "`"
+  in
+  Diagnostic.error (Location.span_of_lexing start stop) "syntax error: unexpected %s" token
+
+let expression text =
+  let lexbuf = Lexing.from_string text in
+  try Parser.expr Lexer.token lexbuf with Parsing.Parse_error -> unexpected text lexbuf