perry-codegen: Buffer.isBuffer() not lowered (BufferIsBuffer expression)

[proggeramlug]

Environment

• perry 0.5.92
• macOS arm64 (darwin 25.4.0)
• Node v25.8.0 (reference runtime)

Problem

Buffer.isBuffer(x) fails to compile under the LLVM backend:

Error compiling module '.../connection.ts' with --backend llvm:
  lowering function 'encodeParam': lowering body of 'encodeParam':
  perry-codegen Phase 2: expression BufferIsBuffer not yet supported

The compile still produces a binary because Perry emits an empty stub for the module ("linking with empty stubs"), but the resulting main references _perry_fn_src_connection_ts__connect which doesn't exist, so ld fails:

Undefined symbols for architecture arm64:
  "_perry_fn_src_connection_ts__connect", referenced from: _main
  "_src_connection_ts__init", referenced from: _main
ld: symbol(s) not found for architecture arm64

Node and Bun compile + run the same source cleanly.

Minimal repro

// minrepro.ts
function describe(v: unknown): string {
    if (Buffer.isBuffer(v)) {
        return 'buffer of length ' + v.length;
    }
    return typeof v;
}
console.log(describe(Buffer.from([1, 2, 3])));
console.log(describe('hi'));

perry compile minrepro.ts -o /tmp/minrepro
# → perry-codegen Phase 2: expression BufferIsBuffer not yet supported

Hit in real code

Found by @perry/mysql in encodeParam() — the branch that picked BLOB vs VAR_STRING for prepared-statement parameters. Worked around with a duck-type check:

function isBufferLike(v: unknown): boolean {
    if (v === null || typeof v !== 'object') return false;
    const a = v as { readUInt8?: unknown; length?: unknown };
    return typeof a.readUInt8 === 'function' && typeof a.length === 'number';
}

but the native idiom should Just Work — it's one of the most common Node patterns for Buffer-vs-anything-else dispatch.

Expected

Buffer.isBuffer(x) lowers to the runtime's existing Buffer-tag identity check.

Related

perry check --check-deps reported "Compilation is guaranteed to succeed" despite this expression — separate issue filed.

[proggeramlug]

Fixed in v0.5.95 (commit 962080f). See CLAUDE.md v0.5.95 entry for the bundle changelog covering #78–#82.