fix(diagnostics): reject reserved type-name bindings in every module (issue 0077)

The issue-0076 reserved-type-name binding diagnostic only ran over main-file
decls, so an imported module (or the stdlib) could still declare `s2 := ...`
and reach lowering, where the address-of family loads the whole aggregate and
passes it by value to a `ptr` param — LLVM verifier abort.

Extend coverage to every compiled module: a dedicated `checkBindingNames` walk
(in semantic_diagnostics.zig) visits every var/`:=`/typed-local binding name and
function/lambda/struct-method parameter at any depth, with NO main-file filter,
descending the `namespace_decl` that a `mod :: #import` wraps so imported-module
decls are reached. It tracks each module's source_file (save/restore per node)
so the diagnostic renders against the imported module's text. Rejection still
defers to the parser's `Type.fromName` classifier; the unknown-type check (0064)
stays main-file-only. No lowering special-case; `.identifier`-only address-of
paths are unchanged.

Stdlib audit: the only reserved-name bindings under library/ were two `u1`
locals in ui/renderer.sx (UV coords) — renamed to u_min/u_max/v_min/v_max.

Regression test: examples/1120-diagnostics-imported-reserved-type-name.sx (+
companion mod.sx) — an imported `s2 := ...` now emits the clean diagnostic at
the import's declaration site (exit 1), not an LLVM abort.

Resolves issues 0076 (coverage extension) and 0077.

issues/0076-stack-struct-addrof-passed-by-value.md

@@ -31,8 +31,18 @@
 >   both `update(@h, …)` and `h.update(…)`.
 >
 > Pre-existing example `examples/0904-...` declared locals `s1`/`s2` (incidental
-> names); renamed to `filled`/`empty`. Scope: main-file decls only, matching the
-> pass's existing trusted-imports convention.
+> names); renamed to `filled`/`empty`.
+>
+> **Coverage extension (issue 0077).** The first landing scoped the binding
+> check to main-file decls (matching the unknown-type check's trusted-imports
+> convention); an imported module could still declare `s2 := …` and hit the
+> original LLVM verifier abort. The reserved-name binding diagnostic now runs
+> over EVERY compiled module — imported user modules (descending the
+> `namespace_decl` an `mod :: #import` wraps) AND the stdlib `library/` — and
+> the two `u1` locals in `library/modules/ui/renderer.sx` were renamed
+> accordingly. The unknown-type check (issue 0064) stays main-file-only. See
+> issue 0077 for the imported-module facet and its pinned regression test
+> `examples/1120-diagnostics-imported-reserved-type-name.sx`.
 
 ## Symptom (how it first surfaced)
 

issues/0077-imported-reserved-type-name-binding.md

@@ -0,0 +1,103 @@
+# 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`.