Remove dead code from react_compiler and the node:http2 frame parser

Closed
RO
3mo ago
+230-3438

Net -3,128 lines. Every deletion is a zero-reference symbol confirmed by a rustc --force-warn dead_code fixpoint on the touched crates (not just grep), plus a repo-wide reference search covering generated codegen output.

react_compiler (-1,139)

  • The experimental variant of the derived-computations-in-effects validation (validate_no_derived_computations_in_effects_exp + its 22 exclusive helpers/types, ~1.1k lines in one file). The pipeline only ever calls the non-exp version; the _exp env-config flag is parsed from fixture pragmas but read by nothing, so this was unreachable under every cfg combination. The fixture suite (3,329 tests, including the effect-derived-computations fixtures that set the _exp pragma) passes unchanged.
  • SymbolHost: a back-compat alias for a previous parser-hook API, zero users (DESIGN.md updated to name Host).
  • HirBox: arena-box alias with zero uses.

h2_frame_parser.rs (-2,171)

The pre-engine inbound frame-handling path. Since rewrite_read() routed all inbound bytes through the h2 Connection engine, these were transitively unreachable (private items, so the compiler verdict is exact):

  • 19 handler methods: handle_incomming_payload, handle_window_update_frame, handle_unknown_frame, handle_push_promise_frame, decode_header_block, handle_data_frame, handle_go_away_frame, handle_origin_frame, handle_altsvc_frame, handle_rst_stream_frame, handle_ping_frame, handle_priority_frame, handle_continuation_frame, finish_headers_end_stream, handle_headers_frame, handle_settings_frame, lookup_inbound_stream, read_bytes, dispatch_frame
  • Decode-direction wire helpers only they used: u32_from_bytes, SettingsFlags, UInt31WithReserved::{from, from_bytes}, StreamPriority::from, SettingsPayloadUnit::from, FullSettingsPayload::{update_with, write}, get_http2_common_string + its extern declaration, type HeaderValue, struct Payload
  • Helpers with no remaining callers: dispatch_with_3_extra, send_settings_ack, adjust_window_size, increment_window_size_if_needed
  • Write-only parser/stream state those handlers maintained: current_frame, remaining_length, expecting_continuation, preface_received_len, pending_header_block, pending_header_flags, is_waiting_more_headers, header_block_size, header_block_count, Stream.padding

exe_format (-2)

  • pe::Error::InsufficientSpace: never constructed.

Verification

  • rustc --force-warn dead_code reaches a warning-free fixpoint on bun_react_compiler, bun_runtime, bun_exe_format
  • cargo check on all 10 CI target triples: 10 ok
  • Full debug build
  • test/js/node/http2/node-http2.test.js: 347 pass / 0 fail; h2-conformance + continuation + invalid-padding: 77 pass
  • react-compiler.test.ts + react-compiler-fixtures.test.ts: 3,329 pass / 0 fail
  • test/internal/source-lints/: 78 pass, including the new guard test that keeps these symbols from reappearing

Noted but deliberately not removed

  • compile_result.rs logger-serialization types and the always-empty events/ordered_log fields: zero-referenced, but annotated (unreachable_pub reason) as staged for logger wiring.
  • ReactCompilerOptions placeholder fields (gating, ignore_use_no_forget, ...): write-only, but commented as placeholders for a future flag.
  • The C++ definition of JSC__JSGlobalObject__getHTTP2CommonString in ZigGlobalObject.cpp is now unreferenced from Rust; left for a follow-up since that file has pending changes in other open PRs.
  • ThreadSafeRefCount::release and the h2 outbound-encoder API: no production callers, but covered by unit tests and deliberately staged.

[review] gate passed · iteration 1 · 11 files touched

fails on main (without fix) 
ASAN without fix: 3 failed, 320 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/bundler/transpiler/react-compiler-fixtures.test.ts "test/internal/source-lints/dead-symbols-react-compiler-h2.test.ts"
bun test v1.4.0 (0dad17989)

test/internal/source-lints/dead-symbols-react-compiler-h2.test.ts:
46 |     // Arena box alias with zero uses (HirVec is the one HIR actually uses).
47 |     ["src/react_compiler/hir/mod.rs", /\bHirBox\b/],
48 |     // Type predicate whose only callers were in the removed _exp validation.
49 |     ["src/react_compiler/hir/mod.rs", /\bis_use_state_type\b/],
50 |   ];
51 |   expect(resurrected(checks)).toEqual([]);
                                   ^
error: expect(received).toEqual(expected)

- []
+ [
+   "src/react_compiler/validation/validate_no_derived_computations_in_effects.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/hir/environment_config.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/program.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/program.rs: /\bSymbolHost\b/",
+   "src/re
... (truncated)

release without fix: 3 failed, 1146 skipped
bun test v1.4.0-canary.1 (3a845b7a5)

test/internal/source-lints/dead-symbols-react-compiler-h2.test.ts:
46 |     // Arena box alias with zero uses (HirVec is the one HIR actually uses).
47 |     ["src/react_compiler/hir/mod.rs", /\bHirBox\b/],
48 |     // Type predicate whose only callers were in the removed _exp validation.
49 |     ["src/react_compiler/hir/mod.rs", /\bis_use_state_type\b/],
50 |   ];
51 |   expect(resurrected(checks)).toEqual([]);
                                   ^
error: expect(received).toEqual(expected)

- []
+ [
+   "src/react_compiler/validation/validate_no_derived_computations_in_effects.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/hir/environment_config.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/program.rs: /validate_no_derived_computations_in_effects_exp/",
+   "src/react_compiler/program.rs: /\bSymbolHost\b/",
+   "src/react_compiler/lib.rs: /\bSymbolHost\b/",
+   "src/react_compiler/hir/mod.rs: /\bHirBox\b/",
+   "src/react_compiler/hir/mod.rs: /\bis_use_state_type\b/",
+ ]

- Expected  - 1
+ Received  + 9

      at <anonymous> (/workspace/bun/test/internal/source
... (truncated)
passes on PR (with fix) 
ASAN with fix: 320 skipped
$ BUN_DEBUG_QUIET_LOGS=1 bun scripts/build.ts --profile=debug --quiet test "--reporter=junit" "--reporter-outfile=/tmp/mechgate.xml" test/bundler/transpiler/react-compiler-fixtures.test.ts "test/internal/source-lints/dead-symbols-react-compiler-h2.test.ts"
bun test v1.4.0 (0dad17989)

test/internal/source-lints/dead-symbols-react-compiler-h2.test.ts:
(pass) dead react_compiler symbols do not reappear [20.51ms]
(pass) dead h2_frame_parser inbound-path symbols do not reappear [149.68ms]
(pass) dead exe_format symbols do not reappear [3.03ms]

test/bundler/transpiler/react-compiler-fixtures.test.ts:
(pass) react-compiler upstream fixtures > fixture corpus is present [2.25ms]
(pass) react-compiler upstream fixtures > alias-capture-in-method-receiver > minify.syntax [8.78ms]
(pass) react-compiler upstream fixtures > alias-capture-in-method-receiver-and-mutate > minify.syntax [0.73ms]
(pass) react-compiler upstream fixtures > alias-computed-load > minify.syntax [0.47ms]
(pass) react-compiler upstream fixtures > alias-nested-member-path > minify.syntax [0.49ms]
(pass) react-compiler upstream fixtures > alias-capture-in-method-receiver > compile [39.10ms]
(pass) react-compi
... (truncated)

release with fix: 1146 skipped
$ bun scripts/build.ts --profile=release
[configured] bun-profile → bun (stripped) in 683ms (unchanged)
ninja: Entering directory `/workspace/bun/build/release'
[1/6] gen generated_host_exports.rs
generated_host_exports.rs: 93 exports (host=3, lazy=10, generic=80, rust=0); 239 extern-C blocks audited
[1/6] cargo bun_bin → libbun_rust.a (--target x86_64-unknown-linux-gnu)

  nightly-2026-07-20-x86_64-unknown-linux-gnu unchanged - rustc 1.99.0-nightly (9f36de775 2026-07-19)

   Compiling bun_core v0.0.0 (/workspace/bun/src/bun_core)
   Compiling bun_errno v0.0.0 (/workspace/bun/src/errno)
   Compiling bun_ptr v0.0.0 (/workspace/bun/src/ptr)
   Compiling bun_boringssl_sys v0.0.0 (/workspace/bun/src/boringssl_sys)
   Compiling bun_safety v0.0.0 (/workspace/bun/src/safety)
   Compiling bun_zlib_sys v0.0.0 (/workspace/bun/src/zlib_sys)
   Compiling bun_cares_sys v0.0.0 (/workspace/bun/src/cares_sys)
   Compiling bun_zstd v0.0.0 (/workspace/bun/src/zstd)
   Compiling bun_picohttp v0.0.0 (/workspace/bun/src/picohttp)
   Compiling bun_brotli v
... (truncated)
diff hotspot 
src/exe_format/pe.rs                               |    2 -
 src/react_compiler/DESIGN.md                       |    4 +-
 src/react_compiler/hir/environment_config.rs       |    2 -
 src/react_compiler/hir/mod.rs                      |   11 +-
 src/react_compiler/lib.rs                          |    2 +-
 src/react_compiler/program.rs                      |    7 -
 .../validate_no_derived_computations_in_effects.rs | 1161 +---------
 src/runtime/api/bun/h2_frame_parser.rs             | 2350 +-------------------
 src/runtime/error.rs                               |    3 -
 .../transpiler/react-compiler-fixtures.test.ts     |    6 +-
 .../dead-symbols-react-compiler-h2.test.ts         |  120 +
 11 files changed, 230 insertions(+), 3438 deletions(-)

gate history · 7 passed · 0 rejected · iteration 1

evidence per changed file 
file                                                      reads  edits  tests
src/exe_format/pe.rs                                          0      0      0
src/react_compiler/DESIGN.md                                  0      0      0
src/react_compiler/hir/environment_config.rs                  1      1      0
src/react_compiler/hir/mod.rs                                 2      5      0
src/react_compiler/lib.rs                                     1      2      0
src/react_compiler/program.rs                                 1      1      0
…lidation/validate_no_derived_computations_in_effects.rs      3      3      0
src/runtime/api/bun/h2_frame_parser.rs                        4     17      0
src/runtime/error.rs                                          1      1      0
test/bundler/transpiler/react-compiler-fixtures.test.ts       2      2      0
…nal/source-lints/dead-symbols-react-compiler-h2.test.ts      2      5      0