Primitive List storage and Go ABI#

*msruntime.List remains the authoritative mutable identity. It owns one backing kind: []int64, []float64, []bool, []string, or the boxed []Value fallback. Default numeric semantics remain 64-bit. Generic forwarding and bound operations retain the same pointer; growth updates its header. A captured traversal retains the original array and length, including valid retained tails after shrinking.

Use NewIntList, NewFloatList, NewBoolList, or NewStringList with the exact checked type key and an ordinary typed slice. Each copies into fresh backing with two allocations for a nonempty list. NewList(typeKey, []Value) checks the type and payload before choosing a primitive kind; other payloads remain boxed.

Go consumers must use Len, Cap, Get, Append, Set, and CopySlice instead of Items. Items remains available solely for legacy boxed construction, including previously emitted composite literals; it is nil on typed Lists. Writing that field on a typed List does not mutate its primitive backing. There is no lazy boxed mirror. Boxed() creates an explicit independent boundary copy and must not implement a traversal or writer.

CaptureList(Value) returns a ListRange header without allocating or copying values. Its Len and Int, Float, Bool, String, or Get readers observe captured backing. Iterate(Value) remains rangeable for older emitted programs, now as iter.Seq2[int, Value]; Go callers that indexed its former slice return must use captured readers instead. Map and Set snapshot behavior is unchanged.

NewSizedList and the four NewSized*List constructors reserve exact fresh backing for effectful literals. InitListValue and the four primitive InitList* setters perform non-cancelling construction writes only before FinishListInitialization. Lowering owns cancellation, checked conversions, left-to-right evaluation and source positions, and finishes before publishing. Using an initializer after completion or outside its sized bounds faults. Primitive setters additionally require matching typed backing and write it directly; boxed or differently typed backing faults. InitListValue retains the generic construction boundary. These helpers remain internal Go construction APIs, with no change to Manuscript’s collection surface.

ListAtInt/Float/Bool/String return typed Optional values with Value and Present fields. Their Unwrap(ctx) methods retain the ordinary none fault and entry/delivery cancellation. Box(resultType) produces the ordinary Alternative at a generic boundary. Checked source lowering owns each operation’s source site; it must not fuse away cancellation, evaluation ordering or absence diagnostics.

NewIntCompareFunction and NewFloatCompareFunction accept raw typed bodies. Those bodies own generated tracing and cleanup. The constructor installs ordinary Body and guarded IntCompare/FloatCompare entries, with one source admission, depth guard, source-return handling and cancellation delivery. Profiling falls back through the ordinary source wrapper before typed admission. Passing an already guarded body would double admission and is invalid.

NewCompiledSourceFunction preserves NewSourceFunction’s signature and guarded Body. It marks Function.BorrowedArguments only for raw generated bodies that copy parameter Values and never retain or expose their incoming []Value. Capturing individual copied Values, including mutable references, remains valid. Lowered lambdas use it, and the list callbacks (for_each, map, filter, fold, fold_right, count, find/some/every, flat_map, group_by) share one callback helper that borrows when the labels match exactly: each library invocation owns one argument buffer, so recursive or reentrant traversals have separate buffers. Arbitrary NewFunction and NewSourceFunction callbacks receive fresh arrays. Adapters do not inherit this proof.

ListSorted copies storage and uses typed comparator entries when available. Arbitrary callbacks box once per element in temporary sorting storage, avoiding boxing at every comparison. ListSortInPlace captures backing and swaps it in place, preserving identity and mutation/reallocation semantics; an arbitrary callback reads live captured cells and cannot use a cached mirror.

The natural primitive runtime order is numeric for Int, false before true for Bool, and lexical UTF-8 byte order for String. Float puts NaNs before non-NaNs, orders infinities numerically, and treats signed zeros as equal. Stable sorting retains equal values’ order and zero/NaN bits. A missing comparator for other element kinds faults. The source declarations determine where comparator omission is available; this ABI does not itself add source operations.

Large-literal emission is separately owned by #147 and still needs these constructors. Typed source access/comparator lowering is separately owned by #87. The measurement evidence separates runtime improvements from those compiler dependencies.