Phase 7.2. Query order_by + skip / take

Field	Value
MEP	MEP-54
Status	LANDED
Started	2026-05-28 (GMT+7)
Landed	2026-05-28 (GMT+7)
Tracking PR	#22559
Commit	5e2e396f95

Gate

8 new fixtures cover order_by (ints, strings), skip, take, skip+take, order+take, order+skip+take, and order+filter compositions. All pass under go test ./transpiler3/go/build/... -run TestPhase1Hello/query_.

Lowering decisions

The shared C lowerer emits order by as a __queryN = ListSortAscExpr(__queryN) self-assignment and skip n / take m as a __queryN = ListSliceExpr(__queryN, s, e) self-assignment. Both forms always have the result var aliased on both sides so the in-place sort matches Mochi semantics without an extra clone.

• ListSortAscExpr(xs) lowers to slices.Sort(xs) (a statement) when it appears on the right-hand side of a self-assign; the slices import is registered on demand.
• ListSliceExpr(xs, start, end) lowers to mochiListSlice(xs, int(start), int(end)), a small generic helper that clamps both bounds. The C lowerer encodes skip n with end=INT64_MAX/2 which would panic if fed directly to Go's slice operator, so the helper does the clamp.

mochiListSlice is introduced via a new helper-injection path in the lowerer: addHelper(name) records that a helper is needed; an emittedHelpers pass prepends the helper's RawDecl text before main. The corresponding gotree.RawDecl is a verbatim code block used only by these inline helpers. The pattern keeps the generated file self-contained without an extra runtime module dependency, which matters for the Phase 15 single-file go-module target.

Files changed

File	Purpose
transpiler3/go/lower/stmt.go	Recognise __queryN = ListSortAscExpr(__queryN) -> slices.Sort(__queryN); recognise __queryN = ListSliceExpr(...) -> __queryN = mochiListSlice(...)
transpiler3/go/lower/lower.go	addHelper(name) + emittedHelpers pass; mochiListSlice helper text
transpiler3/go/gotree/	RawDecl node for verbatim helper code
tests/transpiler3/go/fixtures/query_order_*/, query_skip_*/, query_take_*/, ...	8 fixtures

Test set

• 8 TestPhase1Hello/query_* subtests covering order_by / skip / take / their compositions.

Closeout notes

Recognising the self-assign pattern specifically (rather than treating ListSortAscExpr as an arbitrary expression) lets the Go output stay statement-level: slices.Sort(xs) returns nothing, so the C-style "expression that mutates and returns" lowering would have needed an IIFE wrapper. The helper-injection pass is a generic mechanism: every later phase that needs an inline helper (mochiAbsI64, mochiTry, mochiLines, mochiPanicValue, mochiOMap, ...) registers via the same addHelper API.