feat: materialize computed compile-time callbacks

README.md

@@ -124,23 +124,25 @@ ordinary procedures also accept `undefined` as the initializer of a mutable loca
 
 procedures returning fixed arrays or records/tuples containing `type`, such as `types proc() [2]type { return [i16, bool] }` or `config proc() struct { child type, count usize } { return { child = i16, count = 2 } }`, execute entirely at compile time. every argument is explicitly supplied, constant, cached and erased; nested/aliased results, empty shapes and dependent `$N` lengths retain exact shape and mutability. compile-time producers accept ordinary type-array/type-record inputs, and runtime generic procedures accept erased `$` parameters with these shapes. direct projections generate signatures, constructors, storage and defaults; explicit `$()` calls inside producers retain owned values. cache identity uses canonical type leaves without merging distinct nominal types, and copies cannot mutate cached inputs/results. imported diagnostics, shared type-control execution limits and repeatable compilation work through interpreter/native execution. ordinary parameters remain excluded from dependent signatures; use `$N` for lengths. runtime type-array/type-record storage and reflection remain open.
 
-optional `if`/`while` captures also execute in type-producing bodies: `if count |length| { return [length]i16 }` generates storage from an optional `usize`. ordinary checked IR validates each executed guard; present payloads become immutable owned constants with exact scalar/aggregate types and strings, and absent optionals skip the body. while guards observe updated locals on each iteration; captures stay body-local across break/continue and early return. generated lengths/defaults, imported producers, cache identity and repeated compilation preserve these values. null data/function pointers materialize as null, but nonnull pointer/slice/callback-bearing payloads retain the constant-materialization escape boundary.
+optional `if`/`while` captures also execute in type-producing bodies: `if count |length| { return [length]i16 }` generates storage from an optional `usize`. ordinary checked IR validates each executed guard; present payloads become immutable owned constants with exact scalar/aggregate types and strings, and absent optionals skip the body. while guards observe updated locals on each iteration; captures stay body-local across break/continue and early return. generated lengths/defaults, imported producers, cache identity and repeated compilation preserve these values. null data/function pointers materialize as null; callbacks retain source declaration identity, while nonnull data pointers and slices retain the constant-materialization escape boundary.
 
 type-producing bodies also execute scalar/enum `match` statements and type-valued match expressions in initializers, assignments and returns, such as `return match wide { true: i16, false: i8 }`. selected expression arms may themselves be matches. an ordinary checked IR match returns the selected arm index, preserving subject/pattern typing, range boundaries, overlap, unreachable-arm and exhaustiveness diagnostics without checking unexecuted bodies. statement arms retain scoped locals, assignments, early returns and enclosing-loop break/continue; expression selection shares the type-control step bound.
 
 matches also select nested types, array lengths, generic arguments, callback signatures and field defaults in type-producing bodies. for example, `return struct { values [2](match wide { true: i16, false: i8 }) }` generates concrete storage without elaborating the unselected arm. snapshots preserve loop-local type/value bindings, selected literals retain their spelling and source provenance, and nominal results are cached before their recursive fields are expanded. deferred type selection shares the producer's execution bound; failed elaboration retains its original diagnostic without leaving unchecked generated types behind. general type-valued execution remains open.
 
-tagged-union matches in type-producing bodies support immutable by-value payload captures in statements, expressions and nested type/storage positions. for example, `match choice { .count |length|: return [length]i16, .empty: return bool }` uses a captured `usize` to generate storage. grouped variants require identical nonvoid payload types; invalid captures in unselected arms are still diagnosed. selected payloads become owned typed constants, preserving narrow integers, nested aggregates and strings across generated lengths/defaults, loop snapshots and repeatable compilation. pointer/slice/callback-bearing active payloads retain the constant-materialization escape boundary below.
+tagged-union matches in type-producing bodies support immutable by-value payload captures in statements, expressions and nested type/storage positions. for example, `match choice { .count |length|: return [length]i16, .empty: return bool }` uses a captured `usize` to generate storage. grouped variants require identical nonvoid payload types; invalid captures in unselected arms are still diagnosed. selected payloads become owned typed constants, preserving narrow integers, nested aggregates and strings across generated lengths/defaults, loop snapshots and repeatable compilation. data-pointer/slice-bearing active payloads retain the constant-materialization escape boundary below.
 
 ordinary procedures may compute integer, boolean, float and string compile-time arguments and return nested records/tuples, fixed arrays, tagged unions and explicit fallible results from constant inputs, such as `Fixed(i16, length(2))`. calls reuse the ordinary checker, typed IR and interpreter, preserving local type inference, checked arithmetic, mutable locals, range/while loops, break/continue and recursive or specialized helper calls. aggregate and fallible arguments receive their declared context, including dependent `[N]T` parameters; cached specializations compare normalized values, not literal spelling or evaluation identity. returned constants become owned source literals before temporary interpreter storage is released, preserving by-value copies, exact integer types, string bytes, enum/optional fields and IEEE float bits. tagged unions retain their actual discriminant and only the active payload, including nested aggregates and void/zero-cell variants. fallible constants retain success/error identity, composed or payload-bearing errors and void success; `catch` can consume them in generated lengths, defaults and runtime expressions.
 
-`$(expression)` explicitly evaluates a constant expression, including an ordinary procedure call, even in a package without templates. use a typed expression when its shape cannot be inferred independently, such as `$(Point { x = 40 })`; integer literals retain contextual typing. the resulting value works in runtime expressions, bindings, expression statements and array lengths, while the erased expression still receives ordinary checking. each interpreter evaluation is isolated and limited to 100,000 IR instructions/terminators and 128 active frames; failures retain their originating source locations. runtime parameters and mutable local/global dependencies cannot supply compile-time inputs. data pointers, slices, callbacks and untagged unions cannot escape temporary evaluation as generated constants; active payloads or aggregate fields containing unsupported values are diagnosed rather than retaining interpreter handles. untagged unions lack an active-member identity, so selecting a source variant could discard observable bytes. executed foreign calls remain interpreter traps. general type-valued execution, metadata reflection and existing generic-library acceptance remain open.
+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 `$(choose())`, compile-time arguments and generated defaults. optional callbacks preserve absence and nested presence; arrays, records, tagged payloads and both fallible channels retain exact callback signatures and specialization-cache identity. imported private targets remain bound to their originating declarations, including across repeated compilation and native emission.
+
+`$(expression)` explicitly evaluates a constant expression, including an ordinary procedure call, even in a package without templates. use a typed expression when its shape cannot be inferred independently, such as `$(Point { x = 40 })`; integer literals retain contextual typing. the resulting value works in runtime expressions, bindings, expression statements and array lengths, while the erased expression still receives ordinary checking. each interpreter evaluation is isolated and limited to 100,000 IR instructions/terminators and 128 active frames; failures retain their originating source locations. runtime parameters and mutable local/global dependencies cannot supply compile-time inputs. nonnull data pointers, slices and untagged unions cannot escape temporary evaluation as generated constants; active payloads or aggregate fields containing unsupported values are diagnosed rather than retaining interpreter handles. untagged unions lack an active-member identity, so selecting a source variant could discard observable bytes. executed foreign calls remain interpreter traps. general type-valued execution and broader existing-library acceptance remain open.
 
 `if $(condition) { ... } else { ... }` evaluates a boolean guard before expanding or checking either body, including calls to ordinary constant-input procedures. concrete generic specializations also select branches whose guards use constants, immutable constant bindings, type comparisons or substituted compile-time parameters. only the selected body is specialized and checked; both bodies are still parsed and name-resolved. selected bodies retain their scope, cleanup and return behavior, and erased guards retain ordinary type checking and source diagnostics. ordinary calls in an implicit guard stay runtime; use `$()` to request their evaluation. optional captures remain runtime, and ordinary nongeneric `if (true)` still checks both bodies.
 
 `compile_error!(message)` requires a compile-time string and reports its owned text at the call site when that body is elaborated. unselected compile-time branches do not report it; ordinary runtime branches remain checked. messages from constant-input procedures retain their bytes through later evaluation, interpreter diagnostics and native executable emission.
 
-`match $(subject) { ... }` selects an expression or statement arm before specializing or checking its body, including ordinary constant-input calls. concrete generic procedures also select matches on side-effect-free constant subjects, including substituted scalar/enum/tagged-union arguments and pure field/index projections. ordinary checked IR validates every pattern and capture declaration before selection; only the selected body is elaborated, while all bodies remain parsed and name-resolved. by-value payload captures retain exact types and owned strings, and selected bodies may use runtime parameters, nested matches, cleanup, returns and enclosing-loop transfers. ordinary call subjects, runtime parameters and mutable locals stay runtime, as do contextual aggregate bindings that might omit runtime defaults; ordinary nongeneric literal matches still check all arms. use `$()` to request explicit evaluation. pointer/slice/callback-bearing payloads retain the escape boundary above.
+`match $(subject) { ... }` selects an expression or statement arm before specializing or checking its body, including ordinary constant-input calls. concrete generic procedures also select matches on side-effect-free constant subjects, including substituted scalar/enum/tagged-union arguments and pure field/index projections. ordinary checked IR validates every pattern and capture declaration before selection; only the selected body is elaborated, while all bodies remain parsed and name-resolved. by-value payload captures retain exact types and owned strings, and selected bodies may use runtime parameters, nested matches, cleanup, returns and enclosing-loop transfers. ordinary call subjects, runtime parameters and mutable locals stay runtime, as do contextual aggregate bindings that might omit runtime defaults; ordinary nongeneric literal matches still check all arms. use `$()` to request explicit evaluation. data-pointer/slice-bearing payloads retain the escape boundary above.
 
 type `==` and `!=` comparisons in compile-time expressions and specializations preserve aliases, nominal declaration identity and structural pointer/array/callback signatures. composed error-set identity and specialization caching ignore member ordering, grouping and repetition. for example, `read proc($T type, value T) i16 { if (T == i16) return value else return value.count }` checks the scalar or record path for each concrete call without requiring both operations on every `T`.