js_parser: accept bigint literal property keys wherever numeric keys are accepted - #38793
js_parser: accept bigint literal property keys wherever numeric keys are accepted#38793robobun wants to merge 3 commits into
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The lookahead that decides whether "static", "get", "set", "async", "accessor" and the TypeScript member modifiers are modifiers (rather than the member name itself) checks whether the next token can start a property name. It listed numeric and string literals but not bigint literals, so "static 2n = 1" was parsed as a field named "static" followed by a stray "2n" and rejected, and "static\n2n = 1" silently became two members. A bigint literal is a NumericLiteral and therefore a valid property name, so add it to the lookahead. The key itself was already parsed correctly when no modifier preceded it.
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Status: ready for review. CI on the final build (f61f14c) is 178 of 179 jobs green; the one red job is unrelated to this change (details below). Reproduced on bun 1.4.0 with CI: the transpiler and bundler suites pass on every lane. The single red job is Debian 13 aarch64, where |
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WalkthroughThe parser now treats bigint literals as valid property keys during contextual modifier detection. Transpiler tests cover TypeScript modifiers, syntax errors, emitted output, and runtime behavior for bigint-keyed class and object properties. ChangesBigint property keys
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In `@test/bundler/transpiler/transpiler.test.js`:
- Line 3024: Remove the exact empty-stderr assertion from the subprocess test
while continuing to drain stderr; validate successful execution through the
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src/js_parser/parse/parse_property.rstest/bundler/transpiler/transpiler.test.js
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LGTM — one-token addition to the modifier lookahead, matching the existing TBigIntegerLiteral arm in the key match above it.
What was reviewed:
- The lookahead list at parse_property.rs:350 —
TBigIntegerLiteralis already handled in the top-level keymatch(line 262 area) and inparse_property_binding; only this list was missing it. - Checked for sibling "could begin a property name" lookahead lists elsewhere in
src/js_parser/— none share this omission (the TS type-skip sites don't accept bigint keys by design). - Tests cover the full modifier matrix (JS + TS), newline/ASI behavior, negative cases (
{ static 1n() {} }, bigint-as-value), and runtime semantics against node.
Extended reasoning...
Overview
Single-line parser fix in src/js_parser/parse/parse_property.rs: adds T::TBigIntegerLiteral to the matches! list that decides whether the token following a contextual keyword (static, get, set, async, accessor, and the TS visibility/readonly/override/declare/abstract modifiers) can begin a property name. The top-level key match in the same function already handles TBigIntegerLiteral, and parse_property_binding in mod.rs does too — this lookahead was the only place it was omitted, inherited from esbuild. Three new tests in transpiler.test.js cover printed output for JS and TS forms plus a spawned runtime check.
Security risks
None. Pure parser lookahead widening; no untrusted-length arithmetic, no allocation, no I/O. The only behavior change is that previously-rejected valid ES syntax now parses, and the newline form (static\n 2n) now matches node and bun's own numeric-key handling.
Level of scrutiny
Low-to-medium. The source change is a one-token addition to an existing matches! arm alongside TNumericLiteral, which is the exact spec analogue (bigint literals are LiteralPropertyNames). All per-modifier logic downstream is unchanged. I grepped src/js_parser/ for other TNumericLiteral lookahead lists that might share the omission — the only candidates are in parse_skip_typescript.rs (type-level object keys / enum members), where TS itself does not accept bigint literal keys, so they're not part of this class.
Other factors
Tests are thorough for a one-line fix: they exercise every modifier arm behind the changed check, the async-newline ASI exception, the "word is the key, not a modifier" fallthrough (static = 1n, { get: 1n }), the static -in-object-literal error, and a runtime fixture asserting field/getter/setter/async/generator/accessor semantics plus prototypeKeys. The runtime test uses tempDir/bunEnv/bunExe (already imported at line 2), drains stdout/stderr/exited concurrently, and asserts stderr and the parsed JSON before exitCode. PR description confirms the tests fail on 1.4.0 and that the broader parser suites still pass.
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The member-name lists in skip_type_script_object_type (interface and type
literal members) and skip_type_script_binding (destructured parameters in
function types and method signatures) had the same omission as the modifier
lookahead in parse_property: numeric and string literals but not bigint
literals, so "interface I { 1n(): void }" and "({ 1n: a }: T) => void" were
rejected while tsc parses both and bun already accepts the numeric forms.
robobun
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LGTM — adds T::TBigIntegerLiteral alongside T::TNumericLiteral in the three property-key lookahead lists that were missing it.
What was reviewed:
- Verified the three touched lists are the only property-key token lists missing bigint; the actual key consumers (
parse_property's top match,parse_property_binding) already handle it. - Checked that downstream handling in each case (modifier restart loop,
found_key/colon paths in the skippers) is identical to the numeric-literal path. - Confirmed the newline-form behavior change (
static\n 2n) now matches node and bun's own numeric-key handling; non-modifier fallbacks (static = 1n,{ get: 1n }) are covered by tests and unaffected.
Extended reasoning...
Overview
Adds T::TBigIntegerLiteral next to T::TNumericLiteral in three "can this token be a property name?" lists: the could_be_modifier_keyword lookahead in parse_property (parse_property.rs:352), the object-pattern member key arm in skip_type_script_binding (parse_skip_typescript.rs:120), and the modifier/key loop in skip_type_script_object_type (parse_skip_typescript.rs:1040). Per the ES spec BigIntLiteral is a NumericLiteral and therefore a LiteralPropertyName, so every position that accepts 2 as a key must accept 2n. The actual key-consuming parsers already handle bigint keys — I verified parse_property's top-level match (line ~270) and parse_property_binding (mod.rs:1176) both have TBigIntegerLiteral arms — so no downstream changes are needed.
Tests are thorough: printed-output assertions for every JS modifier (static/get/set/async/accessor, plus generators and combinations), the TypeScript-only modifiers (public/private/protected/readonly/override/declare/abstract), new rows in the existing types test for object types, interfaces, method signatures, and destructured function-type parameters, and a runtime subprocess test that exercises field/getter/setter/async/static/accessor semantics and asserts the exact Object.getOwnPropertyNames result. Negative cases (non-modifier fallback, { static 1n() {} } error) and the newline forms are covered.
Security risks
None. Pure parser lookahead extension; no allocation, no untrusted-length arithmetic, no new code paths.
Level of scrutiny
Low-to-medium. The change is a mechanical three-line addition of one token variant to existing match lists, following exactly the pattern already used for TNumericLiteral. I grepped every TNumericLiteral occurrence in src/js_parser/parse/ to confirm no other property-key list was missed — the remaining sites are type-value positions (which already have separate bigint arms) or expression prefixes (which already list bigint). The only behavior change to previously-accepted code is the newline form static\n 2n = 1, which now parses as node does and as bun already does for numeric keys.
Other factors
The CodeRabbit stderr concern was resolved in-thread with a valid justification (bunEnv sets BUN_DEBUG_QUIET_LOGS=1; the same file already uses this pattern). No prior reviews from me on this PR. The bug-hunting system found nothing. The PR description notes esbuild has the same omission, so this is a genuine spec gap being closed rather than a port regression.
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Problem
class A { 2n = 1; 4n() {} }(no modifier) already works in bun.static\n 2n = 1becomes a field namedstaticplus an instance field2n,get\n 4n() {}becomes a field namedgetplus a plain method. node (and bun with a numeric key,static\n 2 = 1) produce a static field and a getter..tsfile a class can declare9n() {}but the interface it implements cannot declare9n(): void:1n: stringget a type-checker diagnostic, TS1539, but still parse and emit), and bun accepts each of them with a numeric key.parse_property's key match,parse_property_binding) already handles bigint; only these lookahead and skip lists were missed. The lists are inherited from esbuild, which has the same omission.src/js_parser/parse/parse_property.rs:348: after reading an identifier,parse_propertyonly treats it as a modifier if the next token can start a property name. This is whystatic/get/set/async/accessorand the TypeScript member modifiers are taken as the member name when a bigint key follows.src/js_parser/parse/parse_skip_typescript.rs:1036: the loop inskip_type_script_object_typethat consumes modifiers and the member name of an interface or type literal member.src/js_parser/parse/parse_skip_typescript.rs:119: the member-key arm ofskip_type_script_binding, used for destructured parameters inside function types and method signatures.Fix
T::TBigIntegerLiteralnext toT::TNumericLiteralin each of the three lists. Nothing downstream changes: inparse_propertyevery modifier arm sits behind the one lookahead, so the per-modifier rules (asyncandaccessormust be on the same line as the key,staticonly applies in classes, and so on) now apply to bigint keys exactly as they do to numeric keys; in the two skippers everything after the key is driven by the samefound_key/:handling the numeric path already uses.NumericLiteralin the spec grammar and therefore aLiteralPropertyName, so every position that accepts2as a key must accept2n. node agrees for the JS forms; tsc parses every TypeScript form, and itstranspileModuleoutput matches the new expectations (modifiers erased, key kept, types anddeclare/abstractmembers dropped).static/get/setfollowed by a line break and a bigint key), which now parses the way node and bun's own numeric-key handling already parse it. Everything else either errored before or is unaffected: non-modifier words (staticin an object literal,static = 1n,{ get: 1n }) fall through to the same path as before.test/bundler/transpiler/transpiler.test.js: three new tests (printed output for JS classes and object literals including the newline and non-modifier cases, printed output for the TypeScript member modifiers plusinterface I { 1n(): void }implemented by a class, and a runtime check of field/getter/setter/async/static/accessor members with bigint keys), plus new rows in the existing TypeScripttypestest for object types, interfaces, method signatures and destructured parameters in function types, next to the existing numeric-key rows. All of these fail on bun 1.4.0 and pass with this change; the runtime expectations were produced by node 26 (node has noaccessor, so those two values follow the numeric-key behaviour).bun bd testontranspiler.test.jsand onesbuild/ts,esbuild/default,esbuild/lower,decorators,decorator-metadata,es-decorators,es-decorators-esbuild,ts-use-define-for-class-fields,property: all green.s i gwith the debug build, the same as node; bundling the runtime fixture withbun build --minifyand running the output under node gives the same values as running the source under node.Background
parse_propertyparses one class or object member. For a member that starts with an identifier it reads the word, advances, and then has to decide whether the word was the member's name (static = 1,get() {}) or a modifier of the member that follows (static x,get x() {}). It decides by looking at the next token: if that token could begin a property name, the word is checked against the modifier table and, if it matches, the function restarts on the real key; otherwise the word is the key.skip_type_script_*functions walk over type syntax just far enough to find where it ends and drop it.skip_type_script_object_typehandles{ ... }type literals and interface bodies;skip_type_script_bindinghandles the parameter patterns that can appear inside function types and method signatures (ordinary function declarations use the real binding parser, which already accepts bigint keys). Their job is to accept whatever tsc parses, so a token tsc accepts as a member name has to be in their lists too.TBigIntegerLiteralis the lexer token for a bigint literal such as2n;TNumericLiteralis the token for2. As property names both evaluate to the string"2".