UPLC: handle JS boolean in the Bool constant encoder

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
typescript
Domain
compilers

Research direction

Start in packages/evolution/src/UPLC.ts at the Bool encoder around L954, then read the ConstantValue and constantTerm definitions around L194 and L1282 and the decoder around L660. Add the regression coverage described in the issue and verify that false and true produce different flat bytes, with false decoding to index 0.

Written by the indexing model from the issue text.

Description

bug external-review

Summary

The flat encoder for a Bool constant reads value.index, but ConstantValue also permits a plain JS boolean. A JS false has no .index, so (false).index === 0n is false and the encoder emits the True bit. con bool false and con bool true then produce identical flat bytes, so a script built from a false boolean computes that constant as true. Narrow in practice (parameter application uses con data, never con bool), but the public type invites the call that triggers it.

Affected

packages/evolution/src/UPLC.ts Bool encoder (L954)
packages/evolution/src/UPLC.ts ConstantValue type (L194), constantTerm (L1282)
decoder representation: UPLC.ts (L660)

Fix

Handle the primitive form the type advertises in the encoder, e.g.
const bit = typeof value === "boolean" ? (value ? 1 : 0) : (value.index === 0n ? 0 : 1)
Or drop boolean from ConstantValue so { index } is the only representation and the footgun cannot typecheck.

Regression test

  • given: a program whose body is constantTerm("Bool", false)
  • before fix: flat(con bool false) === flat(con bool true), and decoding flat(con bool false) yields index 1 (True)
  • after fix: flat(con bool false) !== flat(con bool true), and decoding flat(con bool false) yields index 0 (False)

Must FAIL on main today and PASS after the fix.

Reference

Report 11

Dominant language
TypeScript
Stars
22
Forks
30
Avg merge
13h
Merged PRs (30d)
14

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