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AnyScript V1 Spec

Purpose

AnyScript is a tiny TypeScript-like language used to study:

  • tokenization
  • parsing
  • scope binding
  • type checking
  • checker-only syntax
  • type erasure

It is not a runtime language with new semantics. It compiles to plain JavaScript.

Files

  • Source files use the .any extension.
  • Output files are JavaScript with type syntax erased.

Pipeline

source -> tokens -> AST -> binding -> type-check -> emit JS

Syntax

Declarations:

  • let name = expr;
  • let name: Type = expr;
  • const name = expr;
  • const name: Type = expr;
  • function add(a: number, b: number): number { return a + b; }

Statements:

  • block: { ... }
  • expression statement: expr;
  • if (expr) stmt else stmt
  • while (expr) stmt
  • return expr;

Expressions:

  • literals: number, string, boolean, null
  • identifiers
  • grouping: (expr)
  • binary ops: + - * / == != < <= > >=
  • assignment: name = expr
  • function call: foo(a, b)
  • object literal: { key: expr, other: expr }
  • property access: obj.key
  • expr satisfies Type
  • expr as const

Types

Primitive types:

  • number
  • string
  • boolean
  • null

Composite types:

  • object types: { port: number, mode: string }
  • unions: string | number, string | null

Checker Rules

  • variables must be declared before use
  • const cannot be reassigned
  • annotated assignment must be type-compatible
  • object assignability is structural
  • union values can be narrowed inside control-flow branches
  • expr satisfies Type
    • validates assignability
    • does not change runtime emit
    • should preserve the original expression type as much as possible
  • expr as const
    • checker-only
    • valid only on literals in V1
    • preserves literal precision instead of widening immediately

Emit Rules

Erase:

  • type annotations
  • type declarations in function parameters / return positions
  • satisfies
  • as const

Example:

const cfg = { mode: "dev", port: 3000 } satisfies { mode: string, port: number };

emits:

const cfg = { mode: "dev", port: 3000 };

Diagnostics

Every error should belong to one phase:

  • lexing
  • parsing
  • binding
  • type checking