target  : (0,0x4F) MidStr
status  : emitted
from    : discovery snippet 'rt_41' (minimised)

' ---- modProbe.bas
Option Explicit

Public Sub Main()
  Dim v As Variant, s As String
  Mid(s, 1, 1) = "x"
End Sub

target disasm lines:
  modProbe.Sub Main | 401468    4F 0000               MidStr str_4011EC='x'
