Const declarations and compound types

The first milestone implemented const value declarations and the recursive type foundation for pointers and references. Raw pointers are now executable as described in unsafe contexts and pointers. Checked scalar and pointer-slot references are described in checked references.

Const values

const i32 add(const i32 value) {
    const i32 increment = 2;
    return value + increment;
}

i32 main() {
    const i32 answer = add(40);
    copy := answer;
    copy = copy + 1;
    return copy - 1;
}

• A const local requires an initializer, which may execute at runtime.
• Const parameters receive their initial value from the caller.
• Assignment to either is FLECHA-S0005, pointing at the assignment target.
• Missing const local initialization is FLECHA-S0023, pointing at its name.
• Reads produce values without the outer binding qualifier. Copies and inferred declarations remain mutable unless their own declaration says const.
• Top-level const on return and cast types does not make the receiving binding const. It does not change the native ABI.
• Explicit none literals use the destination type’s zero value in declarations, assignments, function arguments, and returns. This applies to mutable and const destinations alike.
• Scope resolution and definite assignment still apply, including shadowing and jumps that skip a declaration’s initializer.
• string retains its owning copy behavior; stringv still requires an initializer and must not outlive its owner. Const does not extend lifetimes.
• Only typed const declarations are implemented; const name := value is not part of this milestone. Const does not imply compile-time evaluation.

Recursive types and aliases

Spelling	Normalized type	Fixed binding	Read-only target
*u8	*u8	No	No
*const u8	*const u8	No	Yes
constptr u8	const *u8	Yes	No
constptr const u8	const *const u8	Yes	Yes
&u8	&u8	No	No
&const u8	&const u8	No	Yes
constref u8	const &u8	Yes	No
constref const u8	const &const u8	Yes	Yes

Each type layer has its own const qualifier. &constptr u8 normalizes to &const *u8; a reference to a raw pointer is representable. Adjacent reference markers use whitespace (& &u8) to distinguish them from the logical && token. const constptr u8 and const const u8 duplicate a qualifier on one layer and are rejected. constval is not reserved.

Syntax nodes retain each layer’s full source range and the range of its const keyword (or alias). Semantic types compare recursively by kind, qualifier, and target, rather than by pointer identity. Diagnostics print expanded type names. Symbols and function signatures retain declared qualifiers; bound value expressions omit only the outer qualifier. Nested qualifiers are never erased by this value-copy normalization.

Current boundary

Scalar and raw-pointer storage can be borrowed with &value; see checked references for qualifier, move, and lifetime rules. Unsupported reference storage shapes emit FLECHA-S0024. Raw pointers use the explicit &raw value operation inside unsafe contexts; see unsafe pointers for executable operations and limits.

Allocation, free, defer, general owner moves, slices, and volatile access remain later work in the implementation plan.

Validation

make test covers lexing, recursive parsing and ranges, aliases, type equality, const diagnostics, lowering, LLVM verification, and the native NativeSemanticTests.ConstDeclarations fixture. The fixture exercises runtime initializers, parameters, scalar casts, shadowing, independent owning string copies, and borrowed views; it prints initialized and exits with 42.

make test-sanitizers runs the same native fixture with the instrumented runtime and leak detection. make test-neovim checks the added keywords and & marker.