UnsupportedFeature

The named construct belongs to the reference assembler, but this asm198x build does not implement the requested behaviour. This is a limitation of the tool, not evidence that your source is invalid. The short diagnostic names the construct and, where known, the missing behaviour.

Check the dialect and CPU first. If they are intentional, use the reference assembler for the affected build or reduce the source to a supported form whose bytes you can verify. Do not delete a directive just because assembly then succeeds: directives can control layout, symbol visibility, memory contents or output containers without emitting an opcode of their own.

Different refusals need different next steps:

• A Lua-disabled build needs the lua Cargo feature, not rewritten Lua.
• An unsupported CPU selection needs the matching implemented CPU/dialect entry point, if one exists. Changing only the directive can change opcodes.
• An output or linker construct needs its container or linking behaviour; a flat binary is not an interchangeable object file or executable.
• A refused lwasm pragma can change parsing or encoding. Removing it is safe only after checking the program under both settings in the reference.
• Clock-dependent directives cannot be reproduced by inventing a timestamp. Keep the input explicit when adapting source for reproducible builds.

The conformance ledger and dialect reference distinguish implemented words, known gaps, and constructs the reference itself refuses for the chosen target. That last category is not this error: matching a reference refusal does not mean asm198x lacks an otherwise valid feature.

When reporting a gap, include the exact spelling, surrounding source, options, reference version and expected bytes or artifacts. That makes the request testable without guessing what a no-op implementation would mean.