SAIL

SAIL (Solidity Advanced Intermediate Language) is the source language of the Core Solidity compiler. It extends Solidity's surface syntax with a statically-typed functional core: parametric polymorphism via forall quantifiers, type classes for constrained overloading, and algebraic data types with exhaustive pattern matching. Every SAIL program is compiled to monomorphic Core IR, named Hull, through specialization, then translated to Yul and assembled into EVM bytecode.

This section documents the SAIL language itself. The chapters are ordered from the most foundational concepts to the most advanced:

• Syntax covers lexical conventions, literals, and the overall structure of a source file.
• Built-ins lists the types, values, and operators available without any import, along with the full set of EVM opcodes accessible inside assembly blocks.
• Variable Declaration and Assignment explains let bindings and mutation.
• Functions describes function signatures, free functions, contract methods, and recursive definitions.
• Assembly Blocks details the rules for embedding raw Yul inside a SAIL function body.
• Datatypes introduces algebraic data type declarations and pattern matching.
• Parametric Polymorphism explains forall quantifiers, type variable instantiation, and the specialization strategy.
• Type Classes covers class declarations, instance declarations, superclass constraints, and the three soundness conditions the compiler enforces.
• Modules describes the import and export system, qualified names, and visibility rules.
• Type Inference explains the bidirectional constraint-based algorithm, what must be annotated explicitly, and the error messages the compiler produces when inference fails.