HowlFrame #90 Phase 3a: experimental defun and call bytecode

[howlcipher]

Summary

Phase 3a makes the experimental HFIR→bytecode path run defun and call. Production -compile-bc is unchanged. Issue #90 stays Partial.

• LowerAST gives defun a name, ordered param edges, and body edges. type_hint, type_hints, type_param, and a return-type symbol between the parameter list and the body are erased, matching the AST bytecode compiler.
• call stores the callee name and ordered arg edges. return has an optional value.
• -compile-hfir-bc / hfir.LowerToBytecode registers a BCFunction and emits the existing CALL and RETURN opcodes. No new opcode and no new capability.
• while is still HFIR_BYTECODE_UNSUPPORTED with no BCProgram. A defun whose body contains while fails the same way. ControlEdges stay empty.
• The model-adapter transport still rejects kind defun, so #88 stays closed.
• write_file and mkdir stay deferred. No Wasm, no module linker, and no production path flip.

Hosts for the new conformance case

tests/conformance/abi_v1/09_defun_call.howl (defun_call in tests/conformance/lowered_hfir_abi_v1.json):

Host	Path
hfir_bytecode	Experimental -compile-hfir-bc, then -run-bc
bytecode	Production -compile-bc (AST bytecode after the gate), then -run-bc. Canonical result
interpreter, go, javascript	Still the AST. Included because this fixture is already in their subset. JavaScript rewrites the root to web_app

Those hosts print 42 and phase3a.

How to test

go test ./internal/hfir/ ./internal/vm/ ./tools/difftest/ -count=1
go test -run TestCompileBcStaysASTWhileHfirBcRejectsWhile -count=1

TestLoweredHFIRABIConformance/defun_call is the shared case. go test ./... passed locally.

Manual:

go run howlframe.go -compile-hfir-bc tests/conformance/abi_v1/09_defun_call.howl -o /tmp/defun.hfbc
go run howlframe.go -run-bc /tmp/defun.hfbc

A while program still compiles and runs with -compile-bc, and -compile-hfir-bc rejects it without writing an artifact.

Journal: docs/journals/2026-09-30_lowered_hfir_abi_phase3a_defun_call.md.

This PR does not mark #90 Done and should not be squash-merged as a completion of that issue.

  

[howlcipher]

Phase 3a looks clean on the fence.

Experimental -compile-hfir-bc gains defun / call / return on existing CALL/RETURN. Production -compile-bc still AST — locked by TestCompileBcStaysASTWhileHfirBcRejectsWhile. while still fail-closed (HFIR_BYTECODE_UNSUPPORTED, no artifact). ControlEdges empty. No new opcodes/caps, no Wasm, no linker/module smuggle, no path flip.

Conformance: 09_defun_call.howl / defun_call across hfir_bytecode + AST hosts. #88 transport still rejects defun. write_file/mkdir out of scope.

#90 stays Partial. CI build green on 6e82439. Hard nos clean — undraft when ready; do not squash-merge as #90 Done.