# Existing source-7 constructor defaults

Compatibility experiment, not proposed grammar. `probe.rs` imports only the
matching existing `oa_core` rlib; it performs no production or Cargo edits.

In a coordinated direct-rustc writer slot:

```powershell
. .local/toolchain/env.ps1
rustc --edition 2024 -D warnings --crate-name constructor_defaults_probe harness/experiments/constructor-defaults-20260911/probe.rs --extern oa_core=.local/target-gnullvm/debug/deps/liboa_core-3e81c616fea1d901.rlib -L dependency=.local/target-gnullvm/debug/deps -C linker=clang.exe -o .local/constructor-defaults-20260911/probe.exe
& .local/constructor-defaults-20260911/probe.exe NEW_ISOLATED_OUTPUT_DIRECTORY
```

Use a fresh output directory when reproducing so the committed evidence is not
overwritten. The rlib SHA256 is
`5018A1FD7286ED9DFEDCBBF5B68B399AD5D143F2A9AAAED3078CFC934C9589C4`.
The exact compiler, core source hashes, executable hash and result inventory
are in `provenance.json`.

`results/results.tsv` records **54 admitted explicit/omitted cases** and
**12 missing-required-field refusals**, covering both OA and SA source 7.
Every admitted occurrence is compared with a literal expected typed body and
the full explicit-case Project. It also requires exact source retention on
stabilization/no-op, a name-only patch retaining omissions, and canonical
format/reparse equality. Both scenario viewpoint omission cases separately
require MixedLegacy equality and canonical stability.

The `.canonical.arcadia` siblings intentionally expand hydrated defaults;
they are not expected to retain authored omission. Exchange `operation none`
is deliberately omitted by canonical serialization. Files named
`omit-bindings`, `omit-kind`, `omit-operator`, `omit-branches`, `omit-guard`, or
`omit-occurrences` are **expected invalid fixtures**, retained to show the
specific missing-field diagnostic. They are not modeling examples.

The program/result files are durable evidence. The compiled executable and
initial/final build logs remain in ignored `.local/constructor-defaults-20260911/`.
Other constructor families and old schema versions were not exhaustively tested.