# 0115 — same-name consts of different shapes collide across modules (panic / silent clobber)

> **RESOLVED** (2026-06-11). Root cause: the globals registry
> (`global_names`) is last-wins across modules and every read/write/addr/
> call site consulted it with no source-awareness; `var_decl` was not even
> a selectable raw author. Fix: `var_decl` joins `RawDeclRef`;
> `selectGlobalAuthor` (the globals analogue of F2's `selectModuleConst`)
> selects the author own-wins / one-flat-visible / ambiguous-loudly and
> serves the AUTHOR's per-source global; all bare-identifier global sites
> (read, addr-of, assignment, fn-ptr call, type inference) route through
> it. `selectModuleConst` gained `.own_opaque` so an own const author with
> no materialized value (unsupported shape, e.g. an array `::` const)
> blocks borrowing another module's same-named const instead of panicking.
> The fn-as-VALUE arm admits raw-facts-only authors (an own fn dropped from
> the global decl list by a flat-merge collision — the 0601 `test` case).
> Regression tests: examples/0835, 0836, 0837. The co-blockers also
> landed: dead-global elimination at emit (unreferenced plain-data globals
> are not emitted) and 1055/1056 no longer pin global error ordinals —
> the full std namespace tail is enabled on top.

**Symptom.** When two modules in one program declare a same-named module
const with DIFFERENT shapes (scalar `K : i64 : 4` vs array
`K : [4]i64 : .[...]`), resolution conflates them instead of selecting
per-author:

- **Observed (minimal repro below)**: compiler PANIC — `unresolved type
  reached LLVM emission` (`src/backend/llvm/types.zig:175`, the
  `.unresolved` sentinel tripwire).
- **Observed (full std-tail topology)**: SILENT WRONG VALUES — a module's
  own scalar `K` reads as the other module's array global (prints the
  array's address or the whole array). Seen corpus-wide when
  `hash :: #import "modules/std/hash.sx"` (hash.sx declares the SHA-256
  `K : [64]i64` table) is added to the std.sx namespace tail: examples
  0786/0787/0788/0789/0791/0793/0794 (same-name-const family), 0162, 0168
  all read hash's `K` instead of their own.
- **Expected**: own-wins / per-author const selection (the documented F2
  semantics — readme "Own-wins holds at every one of those sites") applies
  regardless of the consts' shapes; no cross-shape leakage, no panic.

This blocks the PLAN-STDLIB "full tail" follow-up: fs/process/socket/
json/cli/hash/test cannot join the std.sx namespace tail until same-name
consts are robust across every module pulled into every program.

## Reproduction (panic variant — minimal, standalone)

```sx
// h.sx
K : [4]i64 : .[11, 22, 33, 44];
use_k :: () -> i64 { K[2] }
```

```sx
// main.sx
#import "modules/std.sx";
h :: #import "h.sx";
K : i64 : 4;
main :: () { print("K={} h.use_k={}\n", K, h.use_k()); }
```

Run `main.sx` → panic `unresolved type reached LLVM emission`.
Expected: prints `K=4 h.use_k=33`.

## Reproduction (silent-clobber variant — full topology)

Add the full tail to `library/modules/std.sx` after the existing
`mem/xml/log` lines:

```sx
fs :: #import "modules/std/fs.sx";
process :: #import "modules/std/process.sx";
socket :: #import "modules/std/socket.sx";
json :: #import "modules/std/json.sx";
cli :: #import "modules/std/cli.sx";
hash :: #import "modules/std/hash.sx";
test :: #import "modules/std/test.sx";
```

Run `bash tests/run_examples.sh` → ~50 failures. The const-family
failures (0786 prints `a=4318334368 b=4318334368`, 0162 prints the whole
64-entry array for `K=...`) are this bug. (A flat-importing main + a
namespaced array-K module WITHOUT the tail topology resolves correctly —
the silent variant needs the tail's shape, where hash.sx itself
flat-imports std.sx. The panic variant above is the minimal entry point.)

## Co-blockers observed in the same experiment (note, possibly separate issues)

1. **Eager emission bloat**: with the tail in place, every program emits
   hash's 64-entry `@K` table plus `@OS/@ARCH/@POINTER_SIZE` globals even
   when unused (visible in every pinned `.ir` snapshot). Tail modules'
   globals should emit lazily (only when referenced).
2. **0601-comptime-meta** prints nothing (comptime meta machinery breaks
   with the tail in place — root cause unknown, possibly same-name
   generic/comptime fn last-wins: `isPlainFreeFn` excludes generic /
   comptime authors from own-wins rerouting).
3. **1055/1056 errors-enum-value**: user-visible error ints shift when
   tail modules' error sets join the global error-tag registry (numbering
   coupling, arguably inherent; snapshot fragility at minimum).

## Investigation prompt

Same-name module consts are selected own-wins via `selectModuleConst`
(F2, src/ir/lower/expr.zig ~1641) over `module_const_map` — but ARRAY
consts lower as GLOBALS (`@K = internal global [4 x i64]`), registered in
a different, still last-wins registry (find it: grep the lowering for
where a top-level array const becomes a module global — likely
`lowerGlobalDecl` / the global-var map in src/ir/lower/decl.zig). The
panic happens because the scalar `K`'s type resolution reads the OTHER
author's array shape (or vice versa) and poisons to `.unresolved`.

The fix likely needs:
1. Source-aware selection for the globals registry, mirroring
   `selectModuleConst` (own-wins, ≥2 flat-visible authors → loud
   ambiguity) — including the MIXED scalar/array case where the two
   authors live in different registries today.
2. The 0786-family examples already pin scalar/scalar own-wins; add a
   scalar-vs-array pin (the minimal repro above) once fixed.

Verification: run the panic repro (expect `K=4 h.use_k=33`), then add the
full tail to std.sx and run `bash tests/run_examples.sh` — the const
family (0786/0787/0788/0789/0791/0793/0794, 0162, 0168) must pass; the
remaining tail failures decompose into co-blockers 1-3 above (file
separately if they persist).
