AILang/docs/JOURNAL.md

JOURNAL

Chronological notes for myself. Not every change; only decisions, obstacles, and observations that future iterations will need.

2026-05-07 — Day 0

• Repo initialised. Assignment in CLAUDE.md: LLM-native language, LLVM backend.
• Design decisions captured in docs/DESIGN.md.
• Toolchain: rustc 1.94, llvm-config 22.1.3, clang available.
• Decided against inkwell in favour of LLVM IR text emit. Rationale in DESIGN.md.
• Workspace layout:
  • crates/ailang-core — AST, type, hash, JSON schema
  • crates/ailang-check — typechecker (comes later)
  • crates/ailang-codegen — lowering + LLVM IR emit
  • crates/ail — CLI
• MVP goal: examples/sum.ail.json → binary that prints 55. Achieved.

2026-05-07 — architecture review after the MVP

Still on track? Broadly yes. Concrete observations:

What holds:

• JSON AST + canonical form + content hash are all lego bricks that later tools can build on without a refactor (ail deps, ail diff).
• The LLVM IR text pipeline works as planned. No libllvm version pain.
• The effect set is wired into the type system from the start. Extensible to row-poly without touching the core.

Debt that accrues interest:

1. current_block_label_for_phi is a heuristic (see codegen). On nested if terms it will return the wrong block label, because it scans the body backwards. Ticking, because no test cases trigger it yet. Must be fixed next, before new language features arrive.
2. No typed AST. Codegen reads the source AST directly and relies on the typechecker having run before. Fine for the MVP; once ADTs or closures arrive, I will need a separate typed IR stage (TIR).
3. The hash field is not in the AST. Right now we hash the def object directly. Once I serialise hashes as fields (caching), the hash will need to exclude that field before computation.

Plan iteration 2 (now):

1. Clean up block-label tracking, with a nested-if test.
2. Strings as a literal + io/print_str.
3. Hello-world example as a second E2E test.
4. CLI: --json output for machine consumers wherever it fits.

Plan iteration 3:

ADTs + pattern matching. That is the next big jump. Requires a typed IR stage (TIR), because pattern matching lowers into decision trees, which have a different shape from the AST.

2026-05-07 — iteration 2 done

• Block-label tracking is now robust (nested ifs work). Test max3_picks_largest protects it.
• Strings as Lit::Str { value }, type Str -> LLVM ptr, with io/print_str effect op. examples/hello.ail.json prints a string.
• CLI: manifest --json, builtins --json for tool consumers.
• ail deps [--of NAME] [--json] lists call edges. Effect ops are tagged effect:NAME so a consumer can filter them.

Architecture check: no structural deviations. Codegen still reads the source AST directly (a TIR stage will become necessary with ADTs in iteration 3).

2026-05-07 — iteration 3 done: ADTs

• TypeDef in the AST with ctors. A ctor has name and fields: [Type...].
• Term::Ctor (construction) and Term::Match (pattern matching).
• Patterns: Wild, Var, Lit, Ctor { ctor, fields }. In the MVP, nested ctor patterns are NOT allowed — sub-patterns must be Var or Wild.
• Typechecker with a type registry and ctor_index (ctor name → ADT). In Match, exhaustiveness is checked against the full constructor set. A negative test protects this.
• Codegen: boxed heap layout. Per ctor application, malloc(8 + 8*n) bytes; tag at offset 0, fields from offset 8 (8-byte slots, native typed load/store). Match: load tag + switch + arm blocks + phi at the join.
• examples/list.ail.json (Cons/Nil list, sum_list via match) returns 42.

Surprisingly painless. The architecture decisions from day 0 paid off: opaque ptr in LLVM 22 makes the boxed layout almost glue-free; effect tracking was untouched by ADTs; the JSON AST takes new node types cleanly.

Debt accrued:

1. Codegen still reads the source AST directly. The temptation to push on without TIR was strong — and worked, because my Match restrictions are flat (no nested patterns). Once nested patterns arrive, decision- tree lowering will not stay clean without TIR. Debt acknowledged; not due now.
2. No GC. The heap leaks. Acceptable for demo programs; must be addressed before any longer-running program. Options for Phase 4: refcount, Boehm-GC linkage, region inference.
3. No runtime pretty-printer for ADT values. io/print_int is enough for demos, but a generic show :: a -> Str for ADTs would be valuable. Requires dispatch over the tag — feasible, but not now.

Plan iteration 4:

The next steps are less obvious. Three candidates in priority order:

1. Module system (imports). Right now everything is in a single module. With multiple modules + cross-module hashing the language only becomes practical for several defs.
2. Structured error output (ail check --json). So tools can react to type errors without parsing text.
3. Closures / higher-order functions. Requires closure conversion and is a bigger step.

Iteration 4 will be (1) + (2) — both strengthen the LLM tooling and have moderate risk.

2026-05-07 — workflow change: orchestrator + agent repo

At the user's suggestion, switching to orchestrator mode: I delegate clearly bounded implementation chunks to sub-agents and keep only architecture decisions, reviews, and commit discipline. Four specialised agents drafted: implementer, architect, tester, debugger.

Important correction: the user required the agents not to be hidden in .claude/agents/, but versioned as a visible part of the project under agents/. DESIGN.md gained a new section "Project ecosystem", which records this: AILang is not just a language, but language core + CLI + examples + agents + docs + tests, all of equal weight.

Invocation scheme: the system-prompt body from agents/<name>.md as a prefix before the concrete task + sent to the general-purpose agent. Functionally identical to subagent loading from .claude/agents/, but visible in the repo.

Plan iteration 4 (revised):

The module system is more involved than expected (cross-module hashing, import resolution). First the smaller tooling wins, then the module system as iteration 5:

1. Structured error output (ail check --json with a Diagnostic struct, stable codes like unbound-var, type-mismatch).
2. ail diff <a> <b> — semantic module diff via per-def hash comparison.
3. IR snapshot tests — regression protection for the codegen pipeline.

2026-05-07 — iteration 4 done: LLM tooling consolidation

Three sub-commits, each produced by an ailang-implementer invocation and spot-checked by the orchestrator:

• 93fe723 Iter 4a: ail check --json with a Diagnostic struct (severity, code, message, def, ctx). Stable codes: unbound-var, type-mismatch, arity-mismatch, non-exhaustive-match, unknown-ctor, unknown-ctor-in-pattern, nested-ctor-pattern-not-allowed, duplicate-def, unknown-effect-op, unknown-type, schema-mismatch. API: check_module(&Module) -> Vec<Diagnostic>.
• c652b12 Iter 4b: ail diff <a> <b> [--json] as a structural top-level def diff via BLAKE3 hash. Four categories (added/removed/changed/ unchanged), sorted alphabetically, exit code 1 on diff.
• 74a2005 Iter 4c: IR snapshot tests in crates/ail/tests/snapshots/{sum,max3,hello,list}.ll. Normalisation of target triple. Update via UPDATE_SNAPSHOTS=1 cargo test ir_snapshot_. Mismatch produces an .actual file.

Test count: 28 (previously 19). 7 E2E + 4 IR snapshot + 9 ailang-check + 1 ailang-codegen + 7 ailang-core.

Closed from the debt register:

• Block tracking in codegen has not been a heuristic risk since Iter 2; the explicit current_block: String track is now additionally protected against regression by Iter 4c snapshot tests. Debt closed.

New / sharpened debt:

1. check_module is single-shot — the first error aborts, no multi-diagnostic gathering. The spec was that way, but the format suggests Vec semantics. A real multi-diagnostic refactor will be cheaper once TIR exists (a central error accumulator via a separate stage). Not due now.
2. source_filename in the IR is hard-coded to "<module>.ail". As long as there is only one top-level module, that is platform-stable. With Iter 5 (module system + imports) the path becomes relevant — keep it path-independent at construction time, otherwise the snapshots will tip over.

Plan iteration 5: module system with imports. Cross-module hashing, import resolution, multiple .ail.json files in one build. The multi- diagnostic refactor only after that.

Sub-steps:

• 5a — workspace loader. ailang_core::Workspace { modules: BTreeMap<String, Module> } plus load_workspace(entry: &Path), which follows imports recursively from the entry module. Convention: import { module: "foo" } resolves to <dir>/foo.ail.json next to the entry. Cycle detection. CLI: existing subcommands keep working on a single module; a new ail workspace <entry> lists all reachable modules with hash. Tests: two small example modules with an import relation; cycle test.
• 5b — cross-module typecheck. The typechecker takes &Workspace instead of &Module. Imports are mounted in the env as a namespace (alias.def or, with no alias, module.def). New diagnostic codes: unknown-module, unknown-import, import-cycle, ambiguous-name. Tests per code.
• 5c — cross-module codegen. The emitter produces IR for all modules in the workspace, prefix-mangled with @ail_<module>_<def>. E2E test: a program that uses a function from module B in module A returns the correct result in the binary.
• 5d — tooling adjustments. manifest, describe, deps, diff gain a --workspace mode (recursive). The single mode stays the default for backwards compatibility.

During Iter 5, at construction time keep source_filename path-independent (module name only, no directory prefix), otherwise the IR snapshots will tip over.

2026-05-07 — Iter 5b done: cross-module typecheck

• check_workspace(&Workspace) -> Vec<Diagnostic> as the top-level API. check_module is preserved and internally lifts the module into a trivial workspace.
• Convention for qualified references (recorded in DESIGN.md): Term::Var { name } with exactly one dot = <prefix>.<def>. Prefix is an import alias or module name. No new AST node, no renamed fields ⇒ hashes stay stable; all ir_snapshot_* still green.
• Three new diagnostic codes: unknown-module, unknown-import, invalid-def-name (with ctx.reason: "contains-dot").
• CLI: ail check <entry> now always loads via load_workspace. Workspace load failures become structured diagnostics in JSON mode with codes module-not-found, module-cycle, module-name-mismatch, module-hash-mismatch, schema-mismatch. ail build and ail emit-ir stay per single module (cross-module codegen is 5c).
• Examples: ws_main.ail.json now calls ws_lib.add (observable). New: ws_broken.ail.json (unknown-import), ws_unknown_module.ail.json (unknown-module).
• Tests: 37 green (previously 32). 4 new workspace integration tests in crates/ailang-check/tests/workspace.rs, one new e2e test check_workspace_resolves_import.
• Debt: single-shot diagnostics still in place (multi-diagnostic after 5c). The dot convention covers exactly one dot — nested module paths (a.b.c) do not exist; that would only be a topic with hierarchical modules and currently falls through as unbound-var.

2026-05-07 — Iter 5c done: cross-module codegen

• Mangling break (deliberate). All AILang functions are now called @ail_<module>_<def>, even in single-module programs. The old form @ail_<def> is gone. Strings/const globals analogously (@.str_<module>_<hint>_<idx>, @ail_<module>_<const>). The entry point stays main as C ABI: a define i32 @main() trampoline calls @ail_<entry-module>_main(). If the entry module has no main : () -> Unit !IO, the build fails with MissingEntryMain.
• Workspace lowering. New top-level API ailang_codegen::lower_workspace(ws: &Workspace) -> Result<String> produces a single .ll for the whole workspace. Modules in alphabetical order (BTreeMap order); defs in AST order. Cross-module calls are resolved in codegen via the import map of the calling module — same logic as in the typechecker, locally duplicated with a cross-reference (no shared helper module, because the type worlds differ: the typechecker handles Type, codegen handles FnSig from llvm types).
• CLI. ail build and ail emit-ir now always load the workspace and check/lower it fully. Single-module programs keep working (trivial workspace with one module). emit_ir(m) stays in the codegen crate as a convenience API and internally wraps into a trivial workspace.
• Snapshots regenerated. sum.ll, max3.ll, hello.ll, list.ll show the new mangling. New ws_main.ll snapshot documents the cross-module build: @ail_ws_main_main calls @ail_ws_lib_add.
• Tests. 40 green (previously 37). New: workspace_build_runs_imported_fn (e2e: prints 5), ir_snapshot_ws_main, missing_entry_main_is_error (codegen unit). Existing behaviour tests (sum_1_to_10_is_55, max3_picks_largest, hello_world_str_lit, list_sum_via_match) stay green — behaviour unchanged, only the mangling is new.

Debt closed:

• #19 (source_filename hardening). In the workspace world, source_filename is now uniformly <entry-module>.ail, once per workspace. The previous hard-coded path dot is gone with it.

State: the module system is closed end to end — loader + typecheck + codegen + build see the workspace as a coherent unit. The multi- diagnostic refactor and possibly cross-module ADTs remain for later.

2026-05-07 — Iter 5d done: tooling extended to the workspace

• ail manifest|describe|deps|diff <entry> --workspace now operate across all modules of the workspace. The default without the flag stays single-module for backwards compatibility. Manifest sorts by (module, name), describe accepts dotted notation ws_lib.add, deps emits {from_module, from_def, to_module, to_def} edges, diff compares workspace-wide with added/removed/changed/unchanged_modules and a nested sub-diff per changed_module.
• Refactor: diff_def_lists is the single source of the four-category logic; single and workspace diff share it.
• Tests: 44 green (previously 40). New: manifest_workspace_lists_all_defs, describe_workspace_resolves_qualified_name, deps_workspace_includes_cross_module, diff_workspace_added_module.

Observation (debt): deps does not filter builtins/locals/function parameters. In workspace mode that becomes more visible than in single mode — ws_lib.add lists edges to ws_lib.+ (builtin) and ws_lib.a/ws_lib.b (function parameters). A known pre-existing issue from Iter 2; Task #22 in the backlog.

2026-05-07 — architecture review after Iter 5

Architect agent invoked. Findings:

1. Mangling consistency holds. @ail_<module>_<def> is consistent across functions, constants, string globals, and cross-module calls. The trampoline is correct. ADT constructors are deliberately symbol-free (inline malloc).
2. Module hashes bit-identical since Iter 4. The Iter 5c snapshot regeneration was a codegen-output change, not a hash break.
3. Drift, due now:
   • DESIGN.md says define i64 @main(), codegen emits define i32 @main() (see sum.ll:35).
   • String-schema notation in DESIGN.md was shortened (@.str_<module>_<idx> instead of @.str_<module>_<hint>_<idx>).
4. Debt that accrues interest: the deps builtin leak (Task #22) has become a falsehood in workspace mode — close it before the next big jump.

Plan iteration 6 — clean-up:

1. Fix DESIGN.md drift. Update the mangling-scheme block, correct the @main signature, and note the string globals precisely.
2. deps hardening (#22). Build a top-level def table per workspace; filter edges whose target is not a top-level symbol, or emit them as separate builtin:/local: categories. Function parameters via lexical scope tracking from walk_term.
3. Multi-diagnostic refactor (#20). check_workspace accumulates Vec<Diagnostic> across all defs instead of short-circuiting on the first error. Intra-def may still short-circuit — the value is "see all broken defs at once", not "see all broken sub-terms of one def".

Order: 1 first (doc triviality), then 2 before 3 (deps is a tooling- truth fix, multi-diag is a structural extension).

2026-05-07 — Iter 6 done: deps hardening + multi-diagnose + DESIGN audit

Three things landed together. All small, all KISS — no architecture move, just paying off recorded debt.

1. ail deps filters builtins, params, and let/match bindings (#22).

Before: sum -> +, -, ==, n, sum and ws_lib.add -> ws_lib.+, ws_lib.a, ws_lib.b. After: sum -> sum, ws_lib.add -> ws_lib.add gone (no real deps; only the cross-module call from ws_main remains).

Implementation:

• New helper ailang_check::builtins::value_names(): derives the Var-level builtin names (+ - * / % == != < <= > >= not) from list(), so the install-list and the deps-filter share one source of truth.
• walk_term in crates/ail/src/main.rs now threads a scope set: fn-params seed it; Let adds the bound name for the body only; Match arms add their pattern variables (bind_pattern helper, MVP rule "ctor sub-patterns are Var/Wild") and roll them back after. Var refs that hit scope or builtins are dropped; qualified names (prefix.def) are passed through unconditionally — the typechecker forbids dots in def names, so no shadowing risk.
• Tests added: deps_filters_builtins_params_locals, deps_workspace_filters_builtins_and_params. The Iter 5d test (deps_workspace_includes_cross_module) keeps passing — the only edge it asserted is the legitimate one.

2. check_module / check_workspace are multi-diagnose (#20).

check_in_workspace returns Vec<CheckError> instead of Result<()>. Pass-1 (top-level symbol table) stays fail-fast — corrupt globals would taint every later diagnostic. Type-def installation is fail-fast within a module (env corruption) but the outer module loop continues. The body-check loop is the multi-diagnose layer: each def is checked against the assembled env, errors accumulate, the next def is attempted.

Test: body_errors_accumulate_across_defs — one module with two independent body errors (arity mismatch + unknown var) yields two diagnostics with the right def field. The legacy single-error check keeps working by .into_iter().next()-ing the Vec, so internal snapshot tests in crates/ailang-check/src/lib.rs are unchanged.

Out of scope: intra-def collection. A single fn body with three type errors still reports one. The "see all broken defs at once" goal is met; intra-def will require unification deferral and isn't due now.

3. DESIGN.md What the MVP is NOT audit (#24).

The section was lying: it claimed "No ADTs / pattern matching" (delivered Iter 3) and "Only ints + bools + unit" (strings landed Iter 2). Renamed to What is not (yet) supported, restructured into "not yet" + "what is supported (smoke-tested)". New invariant: this section is meant to be the truth at the end of the latest iteration, not a 2026-05-07-day-0 scope statement.

Architecture check (the user-asked self-questioning):

• Would I use this language now? For non-recursive arithmetic + ADT programs over int/bool/str: yes, comfortably. For anything that needs mapping, folding, generic data structures: no, closures are the blocker. That's the next big sprint, not Iter 7.
• Consistency: DESIGN.md, JOURNAL.md, code, and CLI output now agree on what the language can do. The "What is not (yet) supported" block is the canonical truth surface.
• Visualisation: ail deps --workspace --json is now a clean cross-module call graph (no builtin noise). Good enough for an external graph renderer to consume; a built-in DOT/ASCII renderer is possible future tooling, not "we need it now". KISS.
• Documentation: the agents/ directory is the sub-prompt layer, the JOURNAL is the iteration log, DESIGN.md is the contract. No new doc axes needed at this scale.

Tests: 47 green (previously 44). +2 deps tests in e2e.rs, +1 multi-diag test in crates/ailang-check/tests/workspace.rs.

Plan iteration 7:

Closures + higher-order functions. This is the big jump that DESIGN.md / Day 0 has been pointing at: it requires a typed IR (TIR) stage, closure conversion in lowering, and a heap-aware ABI. The multi-diag refactor in Iter 6 was scoped intentionally minimal — when TIR lands, intra-def diagnostics become structurally cheap and Task #20 gets revisited.