Anonymous record types creates portable pdb that cannot be converted #6728

Compiling code that uses anonymous records with --debug:portable creates a pdb file that crashes Pdb2Pdb with the error "Invalid compressed integer"

Repro steps

type A = { X : int }
let x = {| X = 7 |} // This doesn't work
//let x = { X = 7 } // This does
let Main (argv: string[]) =
    x.ToString().Length

fsc --debug:portable test.fs
pdb2pdb test.exe

Expected behavior

The portable pdb is converted to a desktop pdb

Actual behavior

pdb2pdb complains of an "invalid compressed integer" in the corefx metadata blob reader
https://github.com/dotnet/corefx/blob/a10890f4ffe0fadf090c922578ba0e606ebdd16c/src/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobReader.cs#L478

Known workarounds

Use regular records

Related information

Provide any related information

• Windows 10
• Microsoft (R) F# Compiler version 10.4.0 for F# 4.6
• Pdb2Pdb 1.1.63314