feat: construct uninitialized compile-time type arrays

README.md

@@ -98,7 +98,7 @@ main proc() i16 {
 
 the specialization checkpoint supports type arguments and constant integer, boolean, string, callback and null value arguments; declared value-parameter types survive specialization, including narrow checked arithmetic and optional captures/unwrap. integer arguments are range-checked even when unused, and erased argument expressions still receive ordinary checking. immutable constant expressions may use unary signs, `!`, `+`, `-`, `*`, comparisons and logical operators. type-producing procedures accept ordinary parameters as well as `$` parameters: every argument must be supplied explicitly and evaluate to a constant, and every input participates in specialization caching. for example, `Fixed proc(T type, count usize) type { return struct { values [count]T } }` accepts `Fixed(i16, 2)` and reuses its nominal type for equivalent inputs. use `$` when a parameter must be visible in subsequent signature annotations. runaway specialization is diagnosed at 128 nested evaluation/specialization calls or 4096 instances.
 
-type-producing bodies support mutable type and value locals, direct binding assignment, scoped blocks, conditional/early returns, integer range and while loops, break/continue and nested/recursive type-producing calls. for example, start with `Result := T`, repeat `Result = [2]Result` in a loop, then `return Result` to generate nested array storage. snapshots retain each local's current value without changing the source AST; scalar operations reuse checking, typed IR and interpreter execution, preserving exact types and overflow diagnostics. type-control execution is limited to 4096 statement/loop-guard steps shared with nested producers; individual scalar evaluations retain the interpreter limits below. only executed bodies are elaborated, while every body is still parsed and name-resolved. cleanup and type-valued record storage in type-producing bodies remain outside this checkpoint.
+type-producing bodies support mutable type and value locals, direct binding assignment, scoped blocks, conditional/early returns, integer range and while loops, break/continue and nested/recursive type-producing calls. for example, start with `Result := T`, repeat `Result = [2]Result` in a loop, then `return Result` to generate nested array storage. snapshots retain each local's current value without changing the source AST; scalar operations reuse checking, typed IR and interpreter execution, preserving exact types and overflow diagnostics. type-control execution is limited to 4096 statement, loop-guard and uninitialized type-array construction steps shared with nested producers; individual scalar evaluations retain the interpreter limits below. only executed bodies are elaborated, while every body is still parsed and name-resolved. cleanup and type-valued record storage in type-producing bodies remain outside this checkpoint.
 
 field/index assignments also update initialized, materializable aggregate locals in type-producing bodies, including nested record fields and mutable fixed-array elements. for example, `counts [2]mut usize := [0, 0]` followed by `counts[1] = 2` can generate `[counts[1]]i16` storage. each update uses ordinary checked IR and returns a new owned constant: earlier copies remain unchanged, while later loop iterations, generated lengths and defaults observe the update. ordinary mutability, index-type/bounds, field and exact value-type checks still apply, including immutable payload captures and narrow arithmetic overflow. imported producers and repeated compilation retain source diagnostics and nominal cache identity; pointer/slice-backed mutation and type-valued record storage remain open.
 
@@ -106,7 +106,9 @@ type-producing bodies also iterate materializable fixed arrays and strings with
 
 initialized fixed arrays of `type` live entirely inside compile-time execution, including nested arrays, explicit/inferred annotations, `.len`, checked `usize` indexing and collection captures. for example, `types [2]mut type := [i8, bool]`, then `types[1] = i16` and `return [types.len]types[1]`, generates `[2]i16` without runtime type metadata. whole-array and nested indexed assignments preserve shape and mutability at every level; copies and loop captures retain earlier values while borrowed array places observe later updates.
 
-procedures returning fixed arrays of `type`, such as `types proc() [2]type { return [i16, bool] }`, also execute entirely at compile time. every argument is explicitly supplied, constant, cached and erased; nested/aliased results, empty shapes and dependent `$N` lengths retain exact shape and mutability. type-producing procedures accept ordinary type-array inputs, and runtime generic procedures accept erased `$types [N]type` parameters. direct projections such as `types()[0]` generate signatures, constructors, storage and defaults; explicit `$()` calls inside producers retain owned array values. cache identity uses canonical type leaves without merging distinct nominal types, and copies cannot mutate cached inputs/results. imported diagnostics, shared type-control execution limits and repeatable compilation work through interpreter/native execution. ordinary parameters remain excluded from dependent signatures; use `$N` for lengths. runtime type-array storage, uninitialized arrays, type-valued record storage and reflection remain open.
+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. `undefined` does not enable runtime storage or ordinary compile-time value-array construction.
+
+procedures returning fixed arrays of `type`, such as `types proc() [2]type { return [i16, bool] }`, also execute entirely at compile time. every argument is explicitly supplied, constant, cached and erased; nested/aliased results, empty shapes and dependent `$N` lengths retain exact shape and mutability. type-producing procedures accept ordinary type-array inputs, and runtime generic procedures accept erased `$types [N]type` parameters. direct projections such as `types()[0]` generate signatures, constructors, storage and defaults; explicit `$()` calls inside producers retain owned array values. cache identity uses canonical type leaves without merging distinct nominal types, and copies cannot mutate cached inputs/results. imported diagnostics, shared type-control execution limits and repeatable compilation work through interpreter/native execution. ordinary parameters remain excluded from dependent signatures; use `$N` for lengths. runtime type-array storage, type-valued 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.