## Summary
Fixes a regression detected by the snapshot-regression corpus.
- Originating discussion:
https://github.com/Z3Prover/bench/discussions/3514
- Benchmark ref: `iss-2795/bug-1.smt2`
## Divergence
```diff
--- bug-1.expected.out (expected)
+++ produced (current z3)
@@ -1 +1,2 @@
+(error "line 3 column 23: invalid declaration, builtin symbol 'pi' has the same argument sorts")
unsat
```
The benchmark declares `(declare-fun pi () Real)`. The expected oracle
is `unsat`; current z3 instead errors out before solving.
## Root cause
Commit 2999517d5 (#10411, "Reject declarations that clash with built-in
signatures") added `cmd_context::builtin_signature_collides`, which
rejects any user declaration whose name resolves to a built-in
application. For **nullary** symbols there are no argument sorts to
distinguish an overload, so this also rejected declarations of
Z3-specific arithmetic *extension* constants such as `pi` and `euler`
(registered as `OP_PI` / `OP_E` in `arith_decl_plugin`). These are not
SMT-LIB reserved symbols and were historically allowed to be shadowed by
user declarations, which is what `iss-2795/bug-1.smt2` relies on.
## Fix
In `builtin_signature_collides`, keep rejecting:
- any collision with `arity > 0` (real overload clash), and
- nullary symbols that resolve into the **basic** theory family (genuine
reserved core constants such as `true`/`false`).
Allow nullary symbols that resolve into non-core theory plugins (e.g.
`pi`, `euler`) to be shadowed. The change is confined to
`src/cmd_context/cmd_context.cpp`.
## Validation
Rebuilt z3 (`make -j8` from `scripts/mk_make.py`) and re-ran the
benchmark:
```
$ ./z3 -T:20 inputs/issues/iss-2795/bug-1.smt2
unsat
```
which now matches the recorded oracle. Also confirmed the intended
#10411 rejections still fire:
- `(declare-fun and (Bool Bool) Int)` -> rejected
- `(declare-const true Bool)` -> rejected
- `(define-fun + ((a Int)(b Int)) Int 0)` -> rejected
- `(declare-fun pi () Real)` / `(declare-fun euler () Real)` -> now
accepted
> [!WARNING]
> <details>
> <summary>Firewall blocked 1 domain</summary>
>
> The following domain was blocked by the firewall during workflow
execution:
>
> - `pypi.org`
>> To allow these domains, add them to the `network.allowed` list in
your workflow frontmatter:
>
> ```yaml
> network:
> allowed:
> - defaults
> - "pypi.org"
> ```
>
> See [Network
Configuration](https://github.github.com/gh-aw/reference/network/) for
more information.
>
> </details>
> Generated by [Fix a Z3 snapshot-regression
divergence](https://github.com/Z3Prover/bench/actions/runs/31074578887)
· 190.8 AIC · ⌖ 19.6 AIC · ⊞ 10.7K ·
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Co-authored-by: z3prover-ci-bot[bot] <305651407+z3prover-ci-bot[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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