// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// This is an X-macro header. It does not use `#include` guards, and instead is
// designed to be `#include`ed after the x-macro is defined in order for its
// inclusion to expand to the desired output. Macro definitions are cleaned up
// at the end of this file.
//
// Supported x-macros are:
// - CARBON_PARSE_NODE_KIND(Name)
//   Used as a fallback if other macros are missing. No kinds should use this
//   directly.
//   - CARBON_PARSE_NODE_KIND_BRACKET(Name, BracketName)
//     Defines a bracketed node kind. BracketName should refer to the node
//     kind that is the _start_ of the bracketed range.
//   - CARBON_PARSE_NODE_KIND_CHILD_COUNT(Name, ChildCount)
//     Defines a parse node with a set number of children, often 0. This count
//     must be correct even when the node contains errors.
//
// This tree represents the subset relationship between these macros, where if a
// specific x-macro isn't defined, it'll fall back to the parent macro.
//
// Parse nodes are clustered based on language feature. Comments will show their
// relationship in postorder, using indentation for child node relationships.

#if !(defined(CARBON_PARSE_NODE_KIND) ||          \
      (defined(CARBON_PARSE_NODE_KIND_BRACKET) && \
       defined(CARBON_PARSE_NODE_KIND_CHILD_COUNT)))
#error "Must define CARBON_PARSE_NODE_KIND family x-macros to use this file."
#endif

// The BRACKET and CHILD_COUNT macros will use CARBON_PARSE_NODE_KIND by default
// when undefined.
#ifndef CARBON_PARSE_NODE_KIND_BRACKET
#define CARBON_PARSE_NODE_KIND_BRACKET(Name, ...) CARBON_PARSE_NODE_KIND(Name)
#endif
#ifndef CARBON_PARSE_NODE_KIND_CHILD_COUNT
#define CARBON_PARSE_NODE_KIND_CHILD_COUNT(Name, ...) \
  CARBON_PARSE_NODE_KIND(Name)
#endif

// The end of the file.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(FileEnd, 0)

// An invalid parse. Used to balance the parse tree. Always has an error.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(InvalidParse, 0)

// An empty declaration, such as `;`.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(EmptyDeclaration, 0)

// A name in a non-expression context, such as a declaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(Name, 0)

// A name in an expression context.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(NameExpression, 0)

// `package`:
//   PackageIntroducer
//   _external_: Name
//     _external_: Literal
//   PackageLibrary
//   PackageApi or PackageImpl
// PackageDirective
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PackageIntroducer, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PackageApi, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PackageImpl, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PackageLibrary, 1)
CARBON_PARSE_NODE_KIND_BRACKET(PackageDirective, PackageIntroducer)

// `namespace`:
//   NamespaceStart
//   _external_: Name or QualifiedDeclaration
// Namespace
CARBON_PARSE_NODE_KIND_CHILD_COUNT(NamespaceStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(Namespace, 2)

// A code block:
//   CodeBlockStart
//   _external_: statements
// CodeBlock
CARBON_PARSE_NODE_KIND_CHILD_COUNT(CodeBlockStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(CodeBlock, CodeBlockStart)

// `fn`:
//     FunctionIntroducer
//     _external_: Name or QualifiedDeclaration
//     _external_: ParameterList
//       _external_: type expression
//     ReturnType
//   FunctionDefinitionStart
//   _external_: statements
// FunctionDefinition
//
// The above is the structure for a definition; for a declaration,
// FunctionDefinitionStart and later nodes are removed and replaced by
// FunctionDeclaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(FunctionIntroducer, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ReturnType, 1)
CARBON_PARSE_NODE_KIND_BRACKET(FunctionDefinitionStart, FunctionIntroducer)
CARBON_PARSE_NODE_KIND_BRACKET(FunctionDefinition, FunctionDefinitionStart)
CARBON_PARSE_NODE_KIND_BRACKET(FunctionDeclaration, FunctionIntroducer)

// A parameter list, possibly deduced:
//   [Deduced]ParamertListStart
//   _external_: [Generic]PatternBinding
//   ParameterListComma
// [Deduced]ParameterList
//
// Expressions and ParameterListComma may repeat with ParameterListComma as a
// separator.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ParameterListStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(DeducedParameterListStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ParameterListComma, 0)
CARBON_PARSE_NODE_KIND_BRACKET(ParameterList, ParameterListStart)
CARBON_PARSE_NODE_KIND_BRACKET(DeducedParameterList, DeducedParameterListStart)

// An array type, such as  `[i32; 3]` or `[i32;]`:
//     ArrayExpressionStart
//     _external_: type expression
//   ArrayExpressionSemi
//   _external_: expression
// ArrayExpression
//
// The bound expression is optional.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ArrayExpressionStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ArrayExpressionSemi, 2)
CARBON_PARSE_NODE_KIND_BRACKET(ArrayExpression, ArrayExpressionSemi)

// A pattern binding, such as `name: Type`:
//   Name
//   _external_: type expression
// [Generic]PatternBinding
//
// Address and Template may be parents to [Generic]PatternBinding, in that
// order.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PatternBinding, 2)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(GenericPatternBinding, 2)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(Address, 1)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(Template, 1)

// `var`:
//   VariableIntroducer
//   _external_: PatternBinding
//   optional VariableInitializer
//   optional _external_: expression
// VariableDeclaration
//
// The VariableInitializer and following expression are paired: either both will
// be present, or neither will.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(VariableIntroducer, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(VariableInitializer, 0)
CARBON_PARSE_NODE_KIND_BRACKET(VariableDeclaration, VariableIntroducer)

// An expression statement:
//   _external_: expression
// ExpressionStatement
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ExpressionStatement, 1)

// `break`:
//   BreakStatementStart
// BreakStatement
CARBON_PARSE_NODE_KIND_CHILD_COUNT(BreakStatementStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(BreakStatement, 1)

// `continue`:
//   ContinueStatementStart
// ContinueStatement
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ContinueStatementStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ContinueStatement, 1)

// `return`:
//   ReturnStatementStart
//   _external_: expression
// ReturnStatement
//
// The child expression is optional.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ReturnStatementStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(ReturnStatement, ReturnStatementStart)

// `for`:
//     ForHeaderStart
//       VariableIntroducer
//       _external_: PatternBinding
//         _external_: type expression
//     ForIn
//     _external_: expression
//   ForHeader
//   _external_: CodeBlock
// ForStatement
//
// Versus a normal `var`, ForIn replaces VariableDeclaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ForHeaderStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(ForIn, VariableIntroducer)
CARBON_PARSE_NODE_KIND_BRACKET(ForHeader, ForHeaderStart)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ForStatement, 2)

// `if` statement + `else`:
//     IfConditionStart
//     _external_: expression
//   IfCondition
//   _external_: CodeBlock
//   IfStatementElse
//   _external_: CodeBlock or IfStatement
// IfStatement
//
// IfStatementElse and the following node are optional based on `else` presence.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IfConditionStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(IfCondition, IfConditionStart)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IfStatementElse, 0)
CARBON_PARSE_NODE_KIND_BRACKET(IfStatement, IfCondition)

// `while`:
//     WhileConditionStart
//     _external_: expression
//   WhileCondition
//   _external_: CodeBlock
// WhileStatement
CARBON_PARSE_NODE_KIND_CHILD_COUNT(WhileConditionStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(WhileCondition, WhileConditionStart)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(WhileStatement, 2)

// Index expressions, such as `a[1]`:
//     _external_: expression
//   IndexExpressionStart
//   _external_: expression
// IndexExpression
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IndexExpressionStart, 1)
CARBON_PARSE_NODE_KIND_BRACKET(IndexExpression, IndexExpressionStart)

// Parenthesized expressions, such as `(2)`:
//   ParenExpressionOrTupleLiteralStart
//   _external_: expression
// ParenExpression
//
// Tuples, such as `(1, 2)`:
//   ParenExpressionOrTupleLiteralStart
//   _external_: expression
//   TupleLiteralComma
// TupleLiteral
//
// Expressions and TupleLiteralComma may repeat with TupleLiteralComma as a
// separator.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ParenExpressionOrTupleLiteralStart, 0)
CARBON_PARSE_NODE_KIND_BRACKET(ParenExpression,
                               ParenExpressionOrTupleLiteralStart)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(TupleLiteralComma, 0)
CARBON_PARSE_NODE_KIND_BRACKET(TupleLiteral, ParenExpressionOrTupleLiteralStart)

// Call expressions, such as `a()`:
//     _external_: expression
//   CallExpressionStart
//   _external_: expression
//   CallExpressionComma
// CallExpression
//
// Expressions and CallExpressionComma may repeat with CallExpressionComma as a
// separator.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(CallExpressionStart, 1)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(CallExpressionComma, 0)
CARBON_PARSE_NODE_KIND_BRACKET(CallExpression, CallExpressionStart)

// A qualified declaration, such as `a.b`:
//   _external_: NameExpression or QualifiedDeclaration
//   _external_: Name
// QualifiedDeclaration
//
// TODO: This will eventually more general expressions, for example with
// `GenericType(type_args).ChildType(child_type_args).Name`.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(QualifiedDeclaration, 2)

// A member access expression, such as `a.b` or
// `GetObject().(Interface.member)`:
//   _external_: lhs expression
//   _external_: rhs expression
// QualifiedExpression
CARBON_PARSE_NODE_KIND_CHILD_COUNT(MemberAccessExpression, 2)

// A pointer member access expression, such as `a->b` or
// `GetObject()->(Interface.member)`:
//   _external_: lhs expression
//   _external_: rhs expression
// QualifiedExpression
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PointerMemberAccessExpression, 2)

// A literal.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(Literal, 0)

// A prefix operator:
//   _external_: expression
// PrefixOperator
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PrefixOperator, 1)

// An infix operator:
//   _external_: lhs expression
//   _external_: rhs expression
// InfixOperator
CARBON_PARSE_NODE_KIND_CHILD_COUNT(InfixOperator, 2)

// The first operand of a short-circuiting infix operator:
//     _external_: expression
//   ShortCircuitOperand
//   _external_: expression
// _external_: InfixOperator
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ShortCircuitOperand, 1)

// A postfix operator:
//   _external_: expression
// PostfixOperator
CARBON_PARSE_NODE_KIND_CHILD_COUNT(PostfixOperator, 1)

// `if` expression + `then` + `else`:
//     _external_: expression
//   IfExpressionIf
//     _external_: expression
//   IfExpressionThen
//   _external_: expression
// IfExpressionElse
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IfExpressionIf, 1)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IfExpressionThen, 1)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(IfExpressionElse, 3)

// Struct literals, such as `{.a = 0}`:
//   StructLiteralOrStructTypeLiteralStart
//       _external_: Name
//     StructFieldDesignator
//     _external_: expression
//   StructFieldValue
//   StructComma
// StructLiteral
//
// Struct type literals, such as `{.a: i32}`:
//       _external_: Name
//     StructFieldDesignator
//     _external_: type expression
//   StructFieldType
//   StructComma
// StructTypeLiteral
//
// Elements (StructFieldValue and StructFieldType, respectively) and StructComma
// may repeat with StructComma as a separator.
//
// When a valid StructFieldType or StructFieldValue cannot be formed, elements
// may be replaced by StructFieldUnknown, which may have a preceding sibling
// StructFieldDesignator if one was successfully parsed.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructLiteralOrStructTypeLiteralStart, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructFieldDesignator, 1)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructFieldValue, 2)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructFieldType, 2)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructFieldUnknown, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(StructComma, 0)
CARBON_PARSE_NODE_KIND_BRACKET(StructLiteral,
                               StructLiteralOrStructTypeLiteralStart)
CARBON_PARSE_NODE_KIND_BRACKET(StructTypeLiteral,
                               StructLiteralOrStructTypeLiteralStart)

// `class`:
//     ClassIntroducer
//     _external_: Name or QualifiedDeclaration
//   ClassDefinitionStart
//   _external_: declarations
// ClassDefinition
//
// The above is the structure for a definition; for a declaration,
// ClassDefinitionStart and later nodes are removed and replaced by
// ClassDeclaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(ClassIntroducer, 0)
CARBON_PARSE_NODE_KIND_BRACKET(ClassDefinitionStart, ClassIntroducer)
CARBON_PARSE_NODE_KIND_BRACKET(ClassDefinition, ClassDefinitionStart)
CARBON_PARSE_NODE_KIND_BRACKET(ClassDeclaration, ClassIntroducer)

// `interface`:
//     InterfaceIntroducer
//     _external_: Name or QualifiedDeclaration
//   InterfaceDefinitionStart
//   _external_: declarations
// InterfaceDefinition
//
// The above is the structure for a definition; for a declaration,
// InterfaceDefinitionStart and later nodes are removed and replaced by
// InterfaceDeclaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(InterfaceIntroducer, 0)
CARBON_PARSE_NODE_KIND_BRACKET(InterfaceDefinitionStart, InterfaceIntroducer)
CARBON_PARSE_NODE_KIND_BRACKET(InterfaceDefinition, InterfaceDefinitionStart)
CARBON_PARSE_NODE_KIND_BRACKET(InterfaceDeclaration, InterfaceIntroducer)

// `constraint`:
//     NamedConstraintIntroducer
//     _external_: Name or QualifiedDeclaration
//   NamedConstraintDefinitionStart
//   _external_: declarations
// NamedConstraintDefinition
//
// The above is the structure for a definition; for a declaration,
// NamedConstraintDefinitionStart and later nodes are removed and replaced by
// NamedConstraintDeclaration.
CARBON_PARSE_NODE_KIND_CHILD_COUNT(NamedConstraintIntroducer, 0)
CARBON_PARSE_NODE_KIND_BRACKET(NamedConstraintDefinitionStart,
                               NamedConstraintIntroducer)
CARBON_PARSE_NODE_KIND_BRACKET(NamedConstraintDefinition,
                               NamedConstraintDefinitionStart)
CARBON_PARSE_NODE_KIND_BRACKET(NamedConstraintDeclaration,
                               NamedConstraintIntroducer)

// The `self` value and `Self` type identifier keywords. Typically of the form
// `self: Self`:
//   SelfValueName
//   SelfTypeNameExpression
// PatternBinding
CARBON_PARSE_NODE_KIND_CHILD_COUNT(SelfValueName, 0)
CARBON_PARSE_NODE_KIND_CHILD_COUNT(SelfTypeNameExpression, 0)

#undef CARBON_PARSE_NODE_KIND
#undef CARBON_PARSE_NODE_KIND_BRACKET
#undef CARBON_PARSE_NODE_KIND_CHILD_COUNT
