The reaching-definitions analysis does not track address loads, so a
variable that is only ever written through its address stays potentially
uninitialized for its whole life. SplitVariables merges every such load
into one live range, which is why csc lowering two deconstructions onto
the same pair of temporaries left neither of them recognizable.
IL cannot express that a method assigns through an address without
reading it first - 'out' is a C# convention over 'ref' - so the address
loads that qualify have to be named. A Deconstruct method is the one
case that matters here, and C#'s definite assignment rules rule out a
read; a Deconstruct method written in IL could read the argument, and
that possibility is knowingly ignored.
Assisted-by: Claude:claude-opus-5:Claude Code
Siegfried Pammer