feat: materialize readonly typed compile-time slices

README.md

@@ -116,7 +116,7 @@ initialized records/tuples containing `type` fields live inside compile-time pro
 
 fixed type arrays may also start with `undefined` inside type/type-array producers: `types [2]mut type := undefined`, then fill `types[index] = i16` in a loop. nested and whole-array updates preserve shape, mutability and independent initialization state in local copies; `.len` is available before elements initialize. reading an uninitialized type leaf, returning an incomplete array or passing one to a compile-time procedure diagnoses a read before initialization. empty shapes are valid, but every dimension must be explicit and nonnegative. construction charges each expanded cell against the shared execution bound, including nested zero-leaf shapes.
 
-ordinary fixed value arrays use the same construction inside type/type-array producers: `counts [2]mut usize := undefined`, then fill indexed elements or replace whole rows/arrays. initialized leaves retain exact scalar, string, optional, record and tagged-union values; local copies retain independent partial initialization state. generated lengths/defaults and compile-time arguments can use initialized elements, while incomplete arrays cannot enter checked IR or procedure arguments. array `.len` and empty shapes do not read leaves. partial type-valued record construction and broader storage-bearing constant materialization beyond readonly byte slices remain unsupported.
+ordinary fixed value arrays use the same construction inside type/type-array producers: `counts [2]mut usize := undefined`, then fill indexed elements or replace whole rows/arrays. initialized leaves retain exact scalar, string, optional, record and tagged-union values; local copies retain independent partial initialization state. generated lengths/defaults and compile-time arguments can use initialized elements, while incomplete arrays cannot enter checked IR or procedure arguments. array `.len` and empty shapes do not read leaves. partial type-valued record construction and constant materialization of mutable slices or nonnull data pointers remain unsupported.
 
 ordinary procedures also accept `undefined` as the initializer of a mutable local with a concrete runtime type, including nested records and fixed arrays. field/index writes initialize storage without reading its previous contents; aggregate copies retain independent contents and initialization state in the interpreter. ordinary compile-time calls can fill this storage and return materializable values, but observing or materializing an uninitialized leaf is diagnosed. native storage uses LLVM poison, not zero initialization: assign every leaf before observing it, and do not rely on native read-before-initialization traps for `undefined` storage. immutable bindings, globals, inferred array lengths and other expression uses remain invalid.
 
@@ -136,7 +136,9 @@ ordinary procedures may compute integer, boolean, float and string compile-time
 
 computed callbacks materialize as references to their original source declarations, never as temporary interpreter function IDs. `choose proc() @proc(value i16) i16 { return increment }` can supply `$(choose())`, compile-time arguments and generated defaults. optional callbacks preserve absence and nested presence; arrays, records, tagged payloads and both fallible channels retain exact callback signatures and specialization-cache identity. imported private targets remain bound to their originating declarations, including across repeated compilation and native emission.
 
-readonly byte-slice results (`[]u8` and `[;sentinel]u8` for any byte sentinel) snapshot their bytes into owned literals before evaluation storage is released. ordinary compile-time helpers can return string subviews, views of locally filled arrays or immutable global arrays, including nested records/arrays, tagged payloads, optionals and both fallible channels. explicit `$()` expressions, generic arguments and generated defaults preserve embedded NULs, arbitrary byte values, exact declared slice types and content-based specialization-cache identity. nonzero-sentinel snapshots retain an owned trailing sentinel outside the logical length; empty views also retain it. snapshots survive evaluation/session disposal and repeated compilation; uninitialized source bytes diagnose read-before-initialization, and sentinel bytes are rechecked after evaluation. mutable slices and nonbyte or nominal-byte slices remain unsupported.
+readonly byte-slice results (`[]u8` and `[;sentinel]u8` for any byte sentinel) snapshot their bytes into owned literals before evaluation storage is released. ordinary compile-time helpers can return string subviews, views of locally filled arrays or immutable global arrays, including nested records/arrays, tagged payloads, optionals and both fallible channels. explicit `$()` expressions, generic arguments and generated defaults preserve embedded NULs, arbitrary byte values, exact declared slice types and content-based specialization-cache identity. nonzero-sentinel snapshots retain an owned trailing sentinel outside the logical length; empty views also retain it. snapshots survive evaluation/session disposal and repeated compilation; uninitialized source bytes diagnose read-before-initialization, and sentinel bytes are rechecked after evaluation.
+
+readonly slices of other materializable element types also own their snapshots, including distinct bytes, wider integers, arrays, records, callbacks and nested readonly slices. generated backing has module lifetime, so returning a computed slice from a runtime helper does not borrow its stack. exact element types, logical lengths, zero-sized elements, full-width signed/unsigned sentinels, nested optional/tagged/fallible channels and content-based specialization identity survive `$()`, compile-time arguments, generated defaults and repeated compilation. snapshots recheck source initialization, address ranges and trailing sentinels; recursive expansion is bounded to 100,000 values and 128 evaluation/serialization levels. mutable slices, nonnull data-pointer elements and address-bearing untagged union elements retain the escape diagnostic.
 
 untagged union constants snapshot every byte of their native-layout storage, including padding and bytes beyond a smaller overlapping member. scalar reinterpretation, nested records/arrays, optionals, tagged payloads, fallible channels and generated defaults preserve exact nominal types and by-value copies through `$()` and compile-time arguments. specialization keys compare the full snapshot, not one selected field. every storage byte must be initialized. because untagged storage has no active-member identity, all member layouts must be free of data pointers, callbacks, strings and slices, recursively; otherwise materialization diagnoses an escape rather than retaining interpreter handles, even if a numeric member was initialized.