`omega` failing due to powers of numerals
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Description
Prerequisites
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- Check that your issue is not already filed:
https://github.com/leanprover/lean4/issues - Reduce the issue to a minimal, self-contained, reproducible test case.
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Description
The following example fails:
example (n : Nat) : 0 ≤ 2 ^ n := by
omega
with the message:
omega could not prove the goal:
a possible counterexample may satisfy the constraints
a ≤ -1
where
a := ↑2 ^ n
At the same time, the following more general example works:
example (m n : Nat) : 0 ≤ m ^ n := by
omega
Context
Related discussion in Zulip: #lean4 > Omega failing due to terms with power?
Steps to Reproduce
Run the code above.
Expected behavior: omega closes the goal above.
Actual behavior: omega fails to close the goal.
Versions
4.22.0-rc3
4.23.0-nightly-2025-07-04
Impact
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Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the minimal omega examples from the issue and compare the failing numeral-base power case with the working general case. Trace the omega implementation from its tactic entry point; done means the first example is closed while the existing general case continues to work.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 45/100