#illusory0x0/printer

#Features

• Partial AST Coverage: Implements printing for core @syntax types from moonbitlang/parser/syntax (33 out of 63 available types)
• Trait-Based Design: Uses SyntaxPrinter trait for consistent, extensible printing behavior
• Code Generation Ready: Designed specifically for code generation workflows, not pretty-printing
• Property-Based Testing: Thoroughly tested using moonbitlang/core packages as test datasets

#Usage

#Basic Printing

///|
test "basic printing" {
  let source = "let value = 42"
  let parsed = @parser.parse_string(source).0.unsafe_head()
  let output = @printer.to_string(parsed)
  inspect(output, content="let value = 42")
}

#Custom Printing

///|
test "custom printing with StringBuilder" {
  let source = "let result = 1 + 2 * 3"
  let parsed = @parser.parse_string(source).0.unsafe_head()
  let builder = StringBuilder::new()
  @printer.SyntaxPrinter::print(parsed, builder)
  let result = builder.to_string()
  inspect(result, content="let result = 1 + 2 * 3")
}

#Function Declarations

///|
test "function declaration printing" {
  let func_source = "fn add(x : Int, y : Int) -> Int { x + y }"
  let parsed = @parser.parse_string(func_source).0.unsafe_head()
  let printed = @printer.to_string(parsed)
  inspect(printed, content="fn add(x : Int, y : Int) -> Int { x + y }")
}

#Type Definitions

///|
test "type definition printing" {
  let type_source = "struct Point { x : Int; y : Int }"
  let parsed = @parser.parse_string(type_source).0.unsafe_head()
  let output = @printer.to_string(parsed)
  inspect(output, content="struct Point { x : Int; y : Int; }")
}

#API Reference

#Core Functions

• to_string[T : SyntaxPrinter](value : T) -> String: Convert any AST node to string
• SyntaxPrinter::print(Self, StringBuilder) -> Unit: Print AST node to StringBuilder

#Supported AST Types

• Expressions: Expr, Constant
• Declarations: FunDecl, TypeDecl, DeclBody, Impl
• Types: Type, TypeName, TypeVarBinder, TypeVarConstraint, ErrorType
• Functions: Func, Parameter, Argument, ArgumentKind
• Patterns: Pattern, ArrayPattern, ArrayPatterns, ConstrPatArg, FieldPat, MapPatElem, DotDotBinder
• Basic Elements: Binder, Var, Label, LongIdent, ConstrName, Constructor, ConstrId
• Other Types: Accessor, SpreadableElem, FieldDef, Visibility

#Design Goals

• Generates syntactically valid MoonBit code
• Maintains semantic equivalence with original AST
• Optimized for code generation pipelines
• Minimal formatting for maximum compatibility

#Testing