public ILRewriter(MethodBase src, MethodBuilder dest,
Func<IILOp, IILRewriteControl, IILRewriteControl> logic)
{
_src = src;
var body = _src.ParseBody();
_originalIL = body.RawIL.ToArray();
body.RawEHC.AssertEmpty();
_body = body.ToReadOnly();
_off2op = _body.ToDictionary(op => op.Offset, op => op).ToReadOnly();
_dest = dest;
_logic = logic;
}