Adds `Term::Seq { lhs, rhs }` (serde tag "seq") as a first-class
AST node for sequencing effectful expressions. Equivalent in
behaviour to `let _ = lhs in rhs`, but the dedicated node gives the
pretty-printer and diagnostics a cleaner shape and surfaces the
intent ("run for effect, then yield rhs") to future tooling.
Typecheck: lhs must be Unit; rhs's type is the result; effects
accumulate.
Codegen: lower lhs (drop SSA), lower rhs (return).
Capture / deps walkers: recurse into both sides.
Refactored examples/list_map.ail.json's print_list to use seq
instead of `let _ = ...`. Output unchanged (2/4/6).
Hash stability: existing examples without Term::Seq serialise
bit-identical; only list_map.ail.json's hashes changed (deliberate
refactor).
Tests: 51 green (was 50). New unit test
`ailang_check::tests::seq_lhs_must_be_unit` covers the type-error
path; existing list_map e2e covers the happy path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Iter 9a — dogfood. examples/list_map.ail.json exercises everything
Iter 1-8 shipped in one program: ADTs (IntList = Nil | Cons Int IntList),
recursive fns over the ADT (map_int, print_list), pattern matching with
nested Var fields, a closure (`\\x. x * 2`, no captures), fn-typed
parameters, IO effects propagating through recursion, and `let`-
sequencing of an effectful sub-expression inside a match arm.
Result: nothing broke. The full pipeline (typecheck → IR emit →
clang → run) produces "2\\n4\\n6\\n". The language is now sufficient
for "small but real" programs.
Iter 9b — `ail run`. Convenience subcommand that builds into a
tempdir and executes, propagating the binary's exit code. Equivalent
to `ail build && ./bin` in one step. Build logic factored out of
`Cmd::Build` into a shared `build_to` helper used by both Build and
Run.
Tests: 50 green (was 49). New e2e `list_map_doubles_then_prints`.
No test for `ail run` itself — the existing build_and_run helper in
e2e.rs already exercises the same build+exec sequence path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Brummel