tomteb
/
carbon-lang


			
				
					
						
						
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							// 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

#ifndef EXECUTABLE_SEMANTICS_AST_STATEMENT_H_
#define EXECUTABLE_SEMANTICS_AST_STATEMENT_H_

#include <list>

#include "executable_semantics/ast/expression.h"

namespace Carbon {

enum class StatementKind {
  ExpressionStatement,
  Assign,
  VariableDefinition,
  If,
  Return,
  Sequence,
  Block,
  While,
  Break,
  Continue,
  Match,
  Continuation,  // Create a first-class continuation.
  Run,           // Run a continuation to the next await or until it finishes..
  Await,         // Pause execution of the continuation.
};

struct Statement;

struct Assignment {
  const Expression* lhs;
  const Expression* rhs;
};

struct VariableDefinition {
  const Expression* pat;
  const Expression* init;
};

struct IfStatement {
  const Expression* cond;
  const Statement* then_stmt;
  const Statement* else_stmt;
};

struct Sequence {
  const Statement* stmt;
  const Statement* next;
};

struct Block {
  const Statement* stmt;
};

struct While {
  const Expression* cond;
  const Statement* body;
};

struct Match {
  const Expression* exp;
  std::list<std::pair<const Expression*, const Statement*>>* clauses;
};

struct Continuation {
  std::string* continuation_variable;
  const Statement* body;
};

struct Run {
  const Expression* argument;
};

struct Statement {
  // TODO: change Statement to a class and make all members private
  int line_num;
  StatementKind tag;

  // Constructors
  static auto MakeExpStmt(int line_num, Expression exp) -> const Statement*;
  static auto MakeAssign(int line_num, Expression lhs, Expression rhs)
      -> const Statement*;
  static auto MakeVarDef(int line_num, Expression pat, Expression init)
      -> const Statement*;
  static auto MakeIf(int line_num, Expression cond, const Statement* then_stmt,
                     const Statement* else_stmt) -> const Statement*;
  static auto MakeReturn(int line_num, Expression e) -> const Statement*;
  static auto MakeSeq(int line_num, const Statement* s1, const Statement* s2)
      -> const Statement*;
  static auto MakeBlock(int line_num, const Statement* s) -> const Statement*;
  static auto MakeWhile(int line_num, Expression cond, const Statement* body)
      -> const Statement*;
  static auto MakeBreak(int line_num) -> const Statement*;
  static auto MakeContinue(int line_num) -> const Statement*;
  static auto MakeMatch(
      int line_num, Expression exp,
      std::list<std::pair<const Expression*, const Statement*>>* clauses)
      -> const Statement*;
  // Returns an AST node for a continuation statement give its line number and
  // contituent parts.
  //
  //     __continuation <continuation_variable> {
  //       <body>
  //     }
  static auto MakeContinuation(int line_num, std::string continuation_variable,
                               const Statement* body) -> const Statement*;
  // Returns an AST node for a run statement give its line number and argument.
  //
  //     __run <argument>;
  static auto MakeRun(int line_num, Expression argument) -> const Statement*;
  // Returns an AST node for an await statement give its line number.
  //
  //     __await;
  static auto MakeAwait(int line_num) -> const Statement*;

  // Access to the alternatives
  const Expression* GetExpression() const;
  Assignment GetAssign() const;
  VariableDefinition GetVariableDefinition() const;
  IfStatement GetIf() const;
  const Expression* GetReturn() const;
  Sequence GetSequence() const;
  Block GetBlock() const;
  While GetWhile() const;
  Match GetMatch() const;
  Continuation GetContinuation() const;
  Run GetRun() const;

 private:
  union {
    const Expression* exp;
    Assignment assign;
    VariableDefinition variable_definition;
    IfStatement if_stmt;
    const Expression* return_stmt;
    Sequence sequence;
    Block block;
    While while_stmt;
    Match match_stmt;
    Continuation continuation;
    Run run;
  } u;
};

void PrintStatement(const Statement*, int);

}  // namespace Carbon

#endif  // EXECUTABLE_SEMANTICS_AST_STATEMENT_H_