Compiler Phases

The plan is not a promise that every phase is complete right now. It is a dependency map that says which invariants must be true before later work can land without becoming a pile of hidden assumptions.

• Phase 1: full type checking and borrow checking.
• Phase 2: HIR lowering and desugaring.
• Phase 3: MIR construction and control-flow lowering.
• Phase 4: runtime library.
• Phase 5 and 6: LLVM codegen and runtime-backed values.
• Phase 12: dynamic stdlib policy and resolution.

• Names are resolved before later passes see them.
• Types are concrete before codegen starts.
• Borrow checking rejects invalid ownership uses early.
• The interpreter stays alive as a behavioural reference.

HIR removes the forms that are convenient for readers but awkward for lowering. It keeps the program tree-shaped, carries concrete types, and makes closures and bindings explicit so later passes do not need to rediscover surface syntax.

• F-strings become formatting primitives plus concatenation.
• ??, ?., ?, and while let lower to explicit control flow.
• Binding sites are assigned stable ids.
• Captured variables are listed explicitly on closures.

• It is a CFG of basic blocks with explicit temporaries.
• Match lowering turns into decision trees.
• Closure conversion becomes an explicit environment value.
• Ownership lowering inserts drops and turns moves into the right operands.

• The backend should translate MIR instead of re-inventing semantics.
• The runtime exists so native binaries can share a stable support layer.
• Differential testing checks compiled behaviour against the interpreter.