Phase 6. Top-level user functions
| Field | Value |
|---|---|
| MEP | MEP-54 |
| Status | LANDED |
| Started | 2026-05-28 (GMT+7) |
| Landed | 2026-05-28 (GMT+7) |
| Tracking PR | #22529 |
| Commit | 9f8c04e82e |
Gate
19 new fixtures cover the user-function surface. Returns by type: fun_return_int, fun_return_float, fun_return_bool, fun_return_string, fun_return_unit. Arg types: fun_arg_string, fun_arg_bool, fun_arg_record, fun_arg_list. Composition: fun_no_args, fun_two_funs, fun_call_twice, fun_pass_var, fun_record_return. Call sites: fun_call_in_if, fun_call_in_loop, fun_call_in_arith. Other: fun_basic (add), fun_recursive (factorial). Run: go test ./transpiler3/go/build/... -run TestPhase1Hello/fun_.
Lowering decisions
Each non-Main aotir.Function lowers to a Go func mochi__<name>(...) <ret> { ... } declaration placed above main. The mangled mochi__ prefix is already stamped on by the shared C lowerer, so call sites need no name resolution: a Mochi add(1, 2) call becomes mochi__add(1, 2) whether it appears in main or in another fun.
Param and return types thread through new helpers paramTypeText and returnTypeText that mirror letTypeText's compound-type dispatch. Both handle the full type surface lit by Phases 0-5: record, union, list, map, set, plus the four scalars. lowerCallExpr produces a gotree.CallExpr for user-function calls used as values; the default branch of CallStmt covers user-function calls used as statements (no return capture).
Recursive functions work without extra lifting because each Go func is a top-level declaration and Go allows self-reference at the package level. Mutual recursion would work similarly; the C lowerer emits both functions, the Go lowerer translates each independently, and Go's forward references handle the order.
Deferred to Phase 6.1: lifted closures (FunLit, Captures, ClosureEnvStmt), first-class function values, TypeFun in lowerType. Phase 6.0 covers the "top-level declarations called by name" pattern; Phase 6.1 then layers lambdas + captures on top.
Files changed
| File | Purpose |
|---|---|
transpiler3/go/lower/lower.go | lowerFunction(fn) -> gotree.FuncDecl for each non-Main function |
transpiler3/go/lower/types.go | paramTypeText, returnTypeText mirror letTypeText |
transpiler3/go/lower/expr.go | lowerCallExpr -> gotree.CallExpr for user-function calls |
transpiler3/go/lower/stmt.go | CallStmt default branch handles user-function call as a statement |
tests/transpiler3/go/fixtures/fun_*/ | 19 fixtures |
Test set
- 19
TestPhase1Hello/fun_*subtests covering return types, arg types, composition, call sites, and recursion.
Closeout notes
The mochi__ prefix means generated Go code never clashes with stdlib names or the runtime helper names (mochiLines, mochiPanic, etc.) which use a mochi prefix without the double underscore. Splitting Phase 6 into 6.0 (top-level functions) and 6.1 (closures) was the right call: Phase 7.1 query DSL only needs top-level functions, so 6.0 unblocked the query work without waiting for the closure infrastructure.