DOCUMENTATION

Sema - Type System & Compatibility

The semantic phase validates and restricts runtime types through the representations defined in src/sema/types/. XCX attempts to guarantee basic static correctness while remaining massively open to implicit dynamic resolutions via heavily overloaded specific nodes.

Type Typology (ty.rs)

The compiler maintains a strict abstraction tree of data shapes:

• Primitives: Type::Int, Type::Float, Type::String, Type::Bool, Type::Date
• Linear Collections: Type::Array(Box<Type>) and Type::Set(SetType)
• Composite Types: Type::Map(Box<Type>, Box<Type>)
• Engine Components: Type::Fiber(Option<Box<Type>>), Type::Table(TableType), Type::Database, Type::DatabaseOperation(DatabaseOpKind, TableType) (pending DB operations such as an unfiltered .remove())
• Dynamic Bindings: Type::Json, Type::Unknown, Type::Builtin(StringId)

The Dynamic Interoperability Philosophy (compat.rs)

compat.rs executes the is_compatible(expected, actual) function. Rather than rigid structural typing, XCX prioritizes fluid interoperability across specific boundaries:

The Unknown Bypass

If either the expected type or the actual type evaluates as Type::Unknown, they are universally compatible. Unknown represents an unauditable expression (like reading an unspecified database query or a custom function return missing a type sig). The semantic checker implicitly surrenders evaluation down to the runtime JIT to avoid halting builds.

The Json Chimera

Type::Json is mathematically compatible with absolutely any expectation across primitive or object assignments. Built-in network outputs and data mutations explicitly return Json, and XCX will accept its mapping into integer arguments or array lists dynamically.

Collection Casting

Arrays and Sets can implicitly down-cast against each other. If an Array:int is assigned or passed into an argument expecting a Set:N, it triggers no error. compat.rs translates the Set's internal abstraction (N, Q, Z, S, B, C) into primitive representations and verifies alignment against the Array's subtype.

Maps enforce standard key-to-key and value-to-value compatibility.

Table Schema Adherence (table_type.rs)

TableType columns carry name, type, is_optional, and has_default, plus is_auto, is_pk, and is_unique (is_auto is load-bearing for row-count checks). For two tables to be compatible, their column layouts must align in length with pairwise is_compatible columns (so Unknown still bypasses); an empty TableType is compatible with any table. Length disparity triggers a type conflict. Set↔Set compatibility is evaluated by base class (N≡Z, S≡C, Q, B); Fiber↔Fiber checks payload compatibility.

Numeric Forgiveness (primitive.rs)

is_numeric_compatible enables specific seamless bridging. Int and Float perfectly overlap. More surprisingly, Int and Date intrinsically interoperate, enabling raw timestamp integer mathematics to implicitly compile directly along raw primitives without explicit casting.