misc: Print document when fatal error is encountered

Add extra context around the document being processed. This helps
pinpoint fatal errors that may come from e.g. parsing of documents but
before did not have a reference to the document that failed to parse.

Author: artempyanykh

Marksman/Doc.fs

@@ -56,23 +56,30 @@ type Doc = {
             | :? Doc as other -> (this :> IComparable<_>).CompareTo(other)
             | _ -> failwith $"Comparison with non-Doc type: {obj}"
 
+exception DocumentError of doc: RootedRelPath * cause: exn with
+    override this.Message =
+        $"Error while processing {RootedRelPath.filename this.doc}{Environment.NewLine}{this.cause.Message}"
+
 
 module Doc =
     open Marksman.Syms
 
     let logger = LogProvider.getLoggerByName "Doc"
 
     let mk parserSettings id version text =
-        let structure = Parser.parse parserSettings text
-        let index = Index.ofCst (Structure.concreteElements structure)
-
-        {
-            id = id
-            version = version
-            text = text
-            structure = structure
-            index = index
-        }
+        try
+            let structure = Parser.parse parserSettings text
+            let index = Index.ofCst (Structure.concreteElements structure)
+
+            {
+                id = id
+                version = version
+                text = text
+                structure = structure
+                index = index
+            }
+        with exn ->
+            raise (DocumentError(id.Path, exn))
 
     let id { id = id } = id
     let text doc = doc.text