# 0077 — reserved type-name binding diagnostic skips imported modules

> **Status: RESOLVED.**
>
> **Root cause:** the reserved-name binding diagnostic (issue 0076) only ran
> over main-file decls (`UnknownTypeChecker.run`'s `main_file` filter). An
> imported module's `s2 := …` was never checked and reached lowering, where the
> address-of family loaded the whole aggregate and passed it by value to a
> `*Box` param — LLVM verifier abort.
>
> **Fix:** the binding check (`checkBindingNames` in
> `src/ir/semantic_diagnostics.zig`) now walks EVERY compiled module — no
> main-file filter — visiting every `var`/`:=`/typed-local binding name and
> function/lambda/struct-method parameter at any depth, and descending the
> `namespace_decl` that a `mod :: #import` wraps so imported-module decls are
> reached. The walk tracks each module's `source_file` (via the diagnostic
> list's `current_source_file`, saved/restored per node) so the diagnostic
> renders against the imported module's text. Rejection still defers to the
> parser's `name_class.Type.fromName` classifier (no drift). The unknown-type
> check (issue 0064) stays main-file-only. No lowering special-case; the
> `.identifier`-only address-of paths are unchanged.
>
> **Stdlib audit:** the only reserved-name bindings under `library/` were two
> `u1` locals in `library/modules/ui/renderer.sx` (lines 203, 382); the UV-coord
> locals were renamed `u_min`/`u_max`/`v_min`/`v_max`. No reserved parameter
> names or other reserved bindings exist in `library/` or `examples/`.
>
> **Regression test:** `examples/1120-diagnostics-imported-reserved-type-name.sx`
> (+ companion `1120-diagnostics-imported-reserved-type-name/mod.sx`) — an
> imported module declaring `s2 := …` now emits the clean diagnostic at the
> import's declaration site (exit 1), not an LLVM abort.

## Symptom

An imported module can still declare a parameter or `var` binding whose name is a
reserved/builtin type name. Observed: the imported-module repro below reaches
lowering and fails LLVM verification by passing a loaded struct value to a
`*Box` parameter. Expected: the same declaration-site diagnostic used for
main-file issue 0076 should reject the imported module's `s2` binding before
lowering.

## Reproduction

Create these two files under the repo root, then run
`./zig-out/bin/sx run .sx-tmp/issue0077_main.sx`.

`.sx-tmp/issue0077_mod.sx`:

```sx
#import "modules/std.sx";

Box :: struct { total: s64 = 0; count: s64 = 0; }

update :: (self: *Box, n: s64) {
    self.total += n;
    self.count += 1;
}

run_imported_reserved_name :: () -> s32 {
    s2 := Box.{ total = 0, count = 0 };
    update(@s2, 5);
    s2.update(7);
    print("imported s2 total={} count={}\n", s2.total, s2.count);
    return 0;
}
```

`.sx-tmp/issue0077_main.sx`:

```sx
#import "modules/std.sx";
mod :: #import ".sx-tmp/issue0077_mod.sx";

main :: () -> s32 {
    return mod.run_imported_reserved_name();
}
```

Current output on `flow/sx-foundation/F0.1`:

```text
LLVM verification failed: Call parameter type does not match function signature!
  %load = load { i64, i64 }, ptr %alloca, align 8, !dbg !461
 ptr  call void @update(ptr %0, { i64, i64 } %load, i64 5), !dbg !462
```

## Investigation prompt

Investigate and fix issue 0077 in the sx compiler. The suspected area is
`src/ir/semantic_diagnostics.zig`, especially
`UnknownTypeChecker.run` and its `main_file` filter. Attempt 2 for issue 0076
added `checkBindingName`, but it only runs over main-file declarations; imported
modules are still trusted and can hit the original LLVM verifier failure. The
fix likely needs to apply reserved-type-name binding diagnostics to all user
source modules that are lowered, while preserving the existing trusted-stdlib
or library convention only where intentionally required. Also audit existing
reserved-name bindings in `library/` (for example `u1 := ...` in
`library/modules/ui/renderer.sx`) and rename any source that will become
newly illegal under the corrected rule.

Verification: run the two-file repro above and expect a clean diagnostic at the
imported module's `s2 := ...` declaration, not LLVM verification failure. Then
run `zig build`, `zig build test`, and `bash tests/run_examples.sh`.