feat: warn on #[derive(Packable)] with sub-optimal packing#21565
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nventuro wants to merge 2 commits intomerge-train/fairiesfrom
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feat: warn on #[derive(Packable)] with sub-optimal packing#21565nventuro wants to merge 2 commits intomerge-train/fairiesfrom
#[derive(Packable)] with sub-optimal packing#21565nventuro wants to merge 2 commits intomerge-train/fairiesfrom
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Emits a compile-time warning when `#[derive(Packable)]` is used on structs with 2+ sub-Field members (bools, integers, arrays of these) that could be bit-packed into fewer Fields manually. Uses `println` as a stopgap since comptime `warn` doesn't exist yet (noir-lang/noir#7714). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
benesjan
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Mar 16, 2026
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This code:
#[derive(Packable)]
struct MyStruct {
a: u128,
b: u128,
}would show the warning even thought the derived implementation would be optimal.
I think this should be handled by counting the bit sizes.
But overall think showing the warning is a very nice approach 👍
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Emits a compile-time warning when
#[derive(Packable)]is used on structs with 2+ sub-Field members (bools, integers, arrays of these) that could be bit-packed into fewer Fields manually. Usesprintlnas a stopgap since comptimewarndoesn't exist yet (noir-lang/noir#7714).