FA-50842 / Raster clipping / Member archive

Clip region expression: swap noop · case 02

Operand swap is lost before a directional region subtraction.

Member previewVariant 2 · 3 implementations · 11 checks per implementation

Case contract

A postfix region program evaluates finite sample sets. Binary operands preserve left/right order. Complement uses the target universe. Named masks are copied on push; duplicate copies the top value. Subtraction, intersection, union and XOR consume both operands. Draw peeks without consuming. Empty-stack operations are outside this bounded contract.

Why this case matters

Raster clip state can leak coverage across draws even when every individual region is valid.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
explicit sequence 1	`[[]]`	`[[0, 1]]`	Failed

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