Module option_lowering

Performs lowering of optional types (T?) and optional expressions within a ProgramScope.

This pass rewrites all optional types into explicit struct representations with two fields:

• is_some: bool — indicating whether the value is present,
• val: T — holding the underlying value (or the “zero” value of T when is_some is false).

All literals, variables, function parameters, and return values involving optional types are transformed into this struct representation. Nested structures (e.g., arrays, tuples, or user-defined structs containing optional types) are lowered recursively.

Example

let x: u8? = 42u8;

is lowered to:

let x: "u8?" = "u8?" { is_some: true, val: 42u8 };

When a value is none, the is_some field is set to false and val is initialized with the zero value of the underlying type (0u8, false, 0field, etc.).

Recursive Lowering Example

let arr: [u64?; 2] = [1u64, none];

is lowered to:

let arr: ["u64?"; 2] = [
    "u64?" { is_some: true, val: 1u64 },
    "u64?" { is_some: false, val: 0u64 },
];

After this pass, no T? types remain in the program: all optional values are represented explicitly as structs with is_some and val fields.

Modules

ast 🔒

program 🔒

visitor 🔒

Structs

OptionLowering

Functions

make_optional_struct_symbol