Need to create the SourceText with the right encoding. See default-encoding and default-encoding compilation option stored in the PDB.

It would probably be better to store the compressed bytes (byte[]) in SourceDocument rather then constructing SourceText here. Then decompress and decode later when we actually need to create the SourceText (at that point we would also have the options decoded from compilation options).

Originally posted by @tmat in #57073 (comment)