HIR - Data Structures

Definitions in src/hir/hir.rs. The shape of HIR is close to AST, but with two key differences: expressions carry a ty: Type field, and local variables are represented as flat indices instead of names in lexical scopes. Note that ty is only populated for literals (Int/Float/String/Bool); every other expression is lowered with Type::Unknown, so codegen does not rely on it for type-driven emission.

Local Variables

HirLocal is a standard u32 index. Lambdas have their own separate index space - their locals start at LAMBDA_LOCAL_OFFSET, so they do not collide with the parent function's locals during lowering or inlining.

Each HirFunc has a locals: Vec<HirLocalDef> vector - the declaration under index i describes the local with index i.

Expressions - HirExpr / HirExprKind

Unlike AST ExprKind, HirExprKind no longer contains nodes that require resolution during the semantic phase (e.g., operator overloads or unresolved references) - this task is performed by the lowering phase, described in hir_lower.md.

The rest of the variants cover the full set of language expressions: literals (IntLiteral, FloatLiteral, StringLiteral, BoolLiteral), variable access (Local, Global), operators (Binary, Unary), calls (FunctionCall, MethodCall, ModuleCall), collections (ArrayLiteral, SetLiteral, MapLiteral), randomness (RandomChoice, RandomInt, RandomFloat), structural access (Index, MemberAccess), Lambda, As, Yield, Tag, and TerminalCommand.

Statements - HirStmt / HirStmtKind

HirStmtKind covers the entire set of AST statements after lowering - declarations (VarDecl), local and global assignments (Assign, AssignGlobal), simple statements (Print, TerminalWrite, Input, ExprStmt, Halt, FunctionCallStmt, Wait, Include, DatabaseDecl), control flow (If, While, For, Break, Continue, Return), JSON operations (JsonBind, JsonBindGlobal, JsonInject, JsonInjectLocal), fibers (FiberDecl, Yield, YieldFrom, YieldVoid), network operations (NetRequestStmt, NetRequestStmtGlobal, Serve), and InlineBlock - the resulting block used when substituting a function body during inlining (see hir_inline.md), with an optional result_local storing the local variable that receives the value returned by the inlined function.

Function - HirFunc

A single instance of HirFunc represents one function or fiber after lowering. is_fiber is read, among other places, by the inlining policy (should_inline in inline_policy.rs) - fibers are never inlined.