Replace ION_MAYBE_UNUSED with compound enum literals and (void) param silences.

Enum literals inline as C compound initializers; unused bindings and parameters use scope-tracked (void) casts instead of blanket unused attributes.

Author: Cod-e-Codes

.cursor/skills/adding-ion-features/SKILL.md

@@ -91,6 +91,7 @@ Add new `TypeCheckError` variants only when existing ones can't express the fail
 - `IRBuilder::build` - keep lowering deterministic
 - `cgen` - generated C must compile with `gcc` + `runtime/ion_runtime.c` (or precompiled `.o` via `test_runner.sh`) + `-lpthread`
 - Multi-file: test with `--mode multi` if imports or visibility involved
+- Warning hygiene under `-Wall -Wextra -Werror`: enum literals use compound initializers (not `_new` helpers); unused locals/params use `(void)` silences via binding read tracking (`scope_mark_binding_read`, `emit_frame_cleanup`), with immediate `(void)` for `_`-prefixed or borrow bindings at registration
 
 ### Project build (`src/build/`)
 

CHANGELOG.md

@@ -2,14 +2,14 @@
 
 ## 2026-06
 
-- **Readiness hardening**: beta compatibility and runtime ABI documents, a lightweight security policy, CLI/`ion-build` multi-error type diagnostics, sanitizer CI smoke (6 tests), and full integration harness `-Wall -Wextra -Werror` on Linux CI. Cgen warning-hygiene improvements (`ION_MAYBE_UNUSED`, binding usage tracking, borrow/defer silences, string literal `.data`/`uint8_t*` casts, string `for...in` length casts), `String` runtime data as `uint8_t*`, and `CFLAGS`/`LDFLAGS` support in the integration harness.
+- **Readiness hardening**: beta compatibility and runtime ABI documents, a lightweight security policy, CLI/`ion-build` multi-error type diagnostics, sanitizer CI smoke (6 tests), and full integration harness `-Wall -Wextra -Werror` on Linux CI. Cgen warning-hygiene improvements (binding usage tracking and `(void)` silences, borrow/defer silences, string literal `.data`/`uint8_t*` casts, string `for...in` length casts), `String` runtime data as `uint8_t*`, and `CFLAGS`/`LDFLAGS` support in the integration harness.
 - **Language**: `for` iteration, `match` guards, `else if`, `break`/`continue`, `loop {}`, `+=`, hex/bin literals, function types `fn(T) -> R`, tuple literals and destructuring. Capture-free fn literals (`fn(T) -> R` lowered to static C function pointers; `ClosureCapture` for outer bindings).
 - **Stdlib & runtime**: `fmt.ion`, `Result<T, E>`, `fs.read_to_string`, `String::push_byte`.
 - **Compiler**: scope-drop codegen, `pthread` spawn, slice bounds checks, array-to-slice coercion, struct/enum field drops, `String` equality, module function name mangling, lasting-borrow rules (ION_SPEC 5.3), field-path borrow exclusivity, move/copy tracking fixes, generic monomorphization, generated C file banner (repo-relative source labels via `portable_source_label`, GNU C note, merged stdlib note, multi-file provenance, comment-safe path escaping).
 - **LSP**: diagnostics, hover, completion, go-to-definition; multi-error reporting; symbol table mirroring; diagnostics cleared on close; hover fixes for `let` bindings and module-qualified calls. Contiguous `//` doc comments attached to declarations (including `pub` items) for hover.
 - **Tooling**: GitHub Actions CI (Linux and Windows), pinned toolchain (1.96.0), `test_expectations.tsv` manifest, `--version`, line-numbered errors, Cursor agent skills. Split `tc` and `cgen` into submodules. `ion-build` driver and `ion.toml` manifests (`single`/`multi`, `out_dir`, `cflags`, `ldflags`, `stdlib_paths`, `emit_in_source`); per-example manifests and `build_hello`/`build_bad_main` harness smoke tests. Shared `discover_import_config` and stdlib search paths for `ion-compiler`, `ion-build`, and LSP. Integration harness precompiles `runtime/ion_runtime.c` once per run (`RUNTIME_OBJ`). `writing-ion-code` agent skill; `creating-ion-skills` examples index lists all eight project skills. Documented checked-in `examples/*.c` codegen snapshots in README and integration-test skill; regenerated example C output. Fixed `researching-pl-literature` skill `paper-seeds` reference formatting.
 - **Docs**: README, CONTRIBUTING, ION_SPEC, and agent skills aligned on project layout, `ion-build` workflow, `emit_in_source`, stdlib import order, LSP features and limitations, `src/build/` checklists, portable Git Bash paths for `test_runner.sh`, and rebuilding release binaries before harness or example C regen (stale `target/release/ion-compiler` note).
-- **Fixes**: match rvalue codegen, `Vec` struct drops, channel codegen, parser handling of `alias::call()`, scope-drop for moved-into-call bindings, HTTP server on Windows, integration harness on Windows. Cgen return-unwind: stop marking bindings dropped after inner-branch `return` (restores outer-path drops), dedupe `_`-prefixed unused silences, mark call arguments moved at emission to avoid double-free on unwind, and unify all function returns via `emit_function_return` (including diverging rvalue `match` arms). Cgen struct field move-out neutralizes owned fields after partial move, deferred to statement end when the move is a call argument; `Vec::push` passes address of struct lvalues; non-generic enums emit before structs; tuple IR uses resolved element types and `tuple_Vec_T` mangling with compound-zero `ret_val` for tuple returns (functions and fn literals). Integer indexing and `Vec<i32>` inference in the type checker. Match rvalue arms: reject diverging arms mixed with value arms; structural control-flow analysis for arm bodies (nested `if`/`else`, `loop` without `break`, `unsafe` blocks); reject mixed diverge and value-producing paths within one arm; cgen assigns through `if`/`else` value branches. `fmt::int_to_string` uses `String::push_byte` per digit instead of per-digit `push_str` branches; integration test asserts `0`, negatives, and `int::MIN`. `int::MIN`/`int::MAX` on integer primitives; `Vec::new()`/`with_capacity()` infer `T` from a `let` type annotation. Clippy fix in `portable_source_label`. `Vec::get`/`Vec::pop`: IR infers `Option<T>` from the vector argument; cgen dereferences `&mut Vec<T>` parameters, unpacks runtime `Option` via `ion_option_from_raw`, and uses a temp for struct-returning `Vec::push`/`Vec::set` call values. Grouped `match` switch arms: scope drops before the case `break` (GCC `-Wimplicit-fallthrough` under `-Werror`); guarded arms in a shared variant case break inside the guard `if` so fallback arms do not run.
+- **Fixes**: match rvalue codegen, `Vec` struct drops, channel codegen, parser handling of `alias::call()`, scope-drop for moved-into-call bindings, HTTP server on Windows, integration harness on Windows. Cgen return-unwind: stop marking bindings dropped after inner-branch `return` (restores outer-path drops), dedupe `_`-prefixed unused silences, mark call arguments moved at emission to avoid double-free on unwind, and unify all function returns via `emit_function_return` (including diverging rvalue `match` arms). Cgen struct field move-out neutralizes owned fields after partial move, deferred to statement end when the move is a call argument; `Vec::push` passes address of struct lvalues; non-generic enums emit before structs; tuple IR uses resolved element types and `tuple_Vec_T` mangling with compound-zero `ret_val` for tuple returns (functions and fn literals). Integer indexing and `Vec<i32>` inference in the type checker. Match rvalue arms: reject diverging arms mixed with value arms; structural control-flow analysis for arm bodies (nested `if`/`else`, `loop` without `break`, `unsafe` blocks); reject mixed diverge and value-producing paths within one arm; cgen assigns through `if`/`else` value branches. `fmt::int_to_string` uses `String::push_byte` per digit instead of per-digit `push_str` branches; integration test asserts `0`, negatives, and `int::MIN`. `int::MIN`/`int::MAX` on integer primitives; `Vec::new()`/`with_capacity()` infer `T` from a `let` type annotation. Clippy fix in `portable_source_label`. `Vec::get`/`Vec::pop`: IR infers `Option<T>` from the vector argument; cgen dereferences `&mut Vec<T>` parameters, unpacks runtime `Option` via `ion_option_from_raw`, and uses a temp for struct-returning `Vec::push`/`Vec::set` call values. Grouped `match` switch arms: scope drops before the case `break` (GCC `-Wimplicit-fallthrough` under `-Werror`); guarded arms in a shared variant case break inside the guard `if` so fallback arms do not run. Cgen: enum literals lower to compound initializers (no per-variant `_new` helpers); unused bindings and parameters silenced with `(void)` at scope unwind instead of blanket `ION_MAYBE_UNUSED`.
 - **Examples**: `text_summary` (fixture file), `data_lib` (multi-module), `channel_worker` (flat single-file), `todo_demo` (interactive stdin, `Vec` of structs with `String`). Per-example `*.toml` manifests for `ion-build`. `http_server` accepts clients until stdin `quit`.
 - **Multi-file fixes**: merge private struct types for cross-module type checking; per-module C symbol prefixes in multi-file codegen (`io_print_int`); walk-up `runtime/` discovery for nested build directories. Integration tests `test_multi_struct`, `test_multi_fmt_io`. Example policy: each demo under `examples/<name>/` with `ion.toml`; build output under `target/` only (no committed `.c`).
 

docs/ABI.md

@@ -68,7 +68,9 @@ inside `unsafe` blocks may omit those checks.
 Struct layout is C-oriented and field-order preserving in generated C. Enum
 layout is compiler-generated and should be treated as stable only for C emitted
 by the same Ion compiler/runtime version unless a beta release explicitly
-documents a layout guarantee.
+documents a layout guarantee. Enum literals (`Enum::Variant(...)`) lower to C
+compound initializers (`(Enum_T){ .tag = N, .data = { ... } }`); the compiler
+does not emit per-variant `_new` helper functions.
 
 ## Channels and `spawn`