Deferring an inner deconstruction to its enclosing one used to be decided by
matching the enclosing pattern in full, once per inner statement of the same
pattern, discarding everything but the end position.
The same decisions are available without it. A nested Deconstruct call can only
be consumed by an enclosing one that is the immediately preceding statement,
looking through the defensive copy of a struct element; anything else in between
is a barrier that stops the enclosing from reaching this position, so it matches
here instead. That leaves the case where the enclosing call is adjacent but
cannot match anyway, which is decided by the constraint MatchDeconstructionCall
already places on its out-parameters.
The tuple-designation branch no longer needs the position the enclosing run
starts at, so the backward walk that searched for it is gone with it. The added
fixtures pin reconstruction across adjacent deconstructions, whose element
stores that walk used to step through.
Assisted-by: Claude:claude-opus-5[1m]:Claude Code
Only defer to an enclosing designation that can reach this position
The temporaries and element reads of a nested tuple designation are stored back
to back, so a statement of any other kind between the temporary and a read of it
stops the enclosing pattern from consuming that read. Deferring anyway lost the
deconstruction entirely: the enclosing attempt fails and the back-to-front walk
does not return to the position that stepped aside for it, so the reads were left
as the plain element accesses they came from, which master reconstructs.
Assisted-by: Claude:claude-opus-5[1m]:Claude Code
Siegfried Pammer
689af4cdba