// parse.h -- Go frontend parser.     -*- C++ -*-

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#ifndef GO_PARSE_H
#define GO_PARSE_H

class Set_iota_traverse;
class Lex;
class Gogo;
class Named_object;
class Type;
class Typed_identifier;
class Typed_identifier_list;
class Function_type;
class Block;
class Expression;
class Expression_list;
class Struct_field_list;
class Case_clauses;
class Type_case_clauses;
class Select_clauses;
class Statement;
class Label;

// Parse the program.

class Parse
{
 public:
  Parse(Lex*, Gogo*);

  // Parse a program.
  void
  program();

 private:
  // Precedence values.
  enum Precedence
  {
    PRECEDENCE_INVALID = -1,
    PRECEDENCE_NORMAL = 0,
    PRECEDENCE_OROR,
    PRECEDENCE_ANDAND,
    PRECEDENCE_CHANOP,
    PRECEDENCE_RELOP,
    PRECEDENCE_ADDOP,
    PRECEDENCE_MULOP
  };

  // We use this when parsing the range clause of a for statement.
  struct Range_clause
  {
    // Set to true if we found a range clause.
    bool found;
    // The index expression.
    Expression* index;
    // The value expression.
    Expression* value;
    // The range expression.
    Expression* range;

    Range_clause()
      : found(false), index(NULL), value(NULL), range(NULL)
    { }
  };

  // We use this when parsing the statement at the start of a switch,
  // in order to recognize type switches.
  struct Type_switch
  {
    // Set to true if we find a type switch.
    bool found;
    // The variable name.
    std::string name;
    // The location of the variable.
    source_location location;
    // The expression.
    Expression* expr;

    Type_switch()
      : found(false), name(), location(UNKNOWN_LOCATION), expr(NULL)
    { }
  };

  // A variable defined in an enclosing function referenced by the
  // current function.
  class Enclosing_var
  {
   public:
    Enclosing_var(Named_object* var, Named_object* in_function,
		  unsigned int index)
      : var_(var), in_function_(in_function), index_(index)
    { }

    // We put these in a vector, so we need a default constructor.
    Enclosing_var()
      : var_(NULL), in_function_(NULL), index_(-1U)
    { }

    Named_object*
    var() const
    { return this->var_; }

    Named_object*
    in_function() const
    { return this->in_function_; }

    unsigned int
    index() const
    { return this->index_; }

   private:
    // The variable which is being referred to.
    Named_object* var_;
    // The function where the variable is defined.
    Named_object* in_function_;
    // The index of the field in this function's closure struct for
    // this variable.
    unsigned int index_;
  };

  // We store Enclosing_var entries in a set, so we need a comparator.
  struct Enclosing_var_comparison
  {
    bool
    operator()(const Enclosing_var&, const Enclosing_var&);
  };

  // A set of Enclosing_var entries.
  typedef std::set<Enclosing_var, Enclosing_var_comparison> Enclosing_vars;

  // Peek at the current token from the lexer.
  const Token*
  peek_token();

  // Consume the current token, return the next one.
  const Token*
  advance_token();

  // Push a token back on the input stream.
  void
  unget_token(const Token&);

  // The location of the current token.
  source_location
  location();

  // For break and continue we keep a stack of statements with
  // associated labels (if any).  The top of the stack is used for a
  // break or continue statement with no label.
  typedef std::vector<std::pair<Statement*, const Label*> > Bc_stack;

  // Parser nonterminals.
  void identifier_list(Typed_identifier_list*);
  Expression_list* expression_list(Expression*, bool may_be_sink);
  bool qualified_ident(std::string*, Named_object**);
  Type* type();
  bool type_may_start_here();
  Type* type_name(bool issue_error);
  Type* array_type(bool may_use_ellipsis);
  Type* map_type();
  Type* struct_type();
  void field_decl(Struct_field_list*);
  Type* pointer_type();
  Type* channel_type();
  Function_type* signature(Typed_identifier*, source_location);
  bool parameters(Typed_identifier_list**, bool* is_varargs);
  Typed_identifier_list* parameter_list(bool* is_varargs);
  void parameter_decl(bool, Typed_identifier_list*, bool*, bool*);
  bool result(Typed_identifier_list**);
  source_location block();
  Type* interface_type();
  void method_spec(Typed_identifier_list*);
  void declaration();
  bool declaration_may_start_here();
  void decl(void (Parse::*)(void*), void*);
  void list(void (Parse::*)(void*), void*, bool);
  void const_decl();
  void const_spec(Type**, Expression_list**);
  void type_decl();
  void type_spec(void*);
  void var_decl();
  void var_spec(void*);
  void init_vars(const Typed_identifier_list*, Type*, Expression_list*,
		 bool is_coloneq, source_location);
  bool init_vars_from_call(const Typed_identifier_list*, Type*, Expression*,
			   bool is_coloneq, source_location);
  bool init_vars_from_map(const Typed_identifier_list*, Type*, Expression*,
			  bool is_coloneq, source_location);
  bool init_vars_from_receive(const Typed_identifier_list*, Type*,
			      Expression*, bool is_coloneq, source_location);
  bool init_vars_from_type_guard(const Typed_identifier_list*, Type*,
				 Expression*, bool is_coloneq,
				 source_location);
  Named_object* init_var(const Typed_identifier&, Type*, Expression*,
			 bool is_coloneq, bool type_from_init, bool* is_new);
  Named_object* create_dummy_global(Type*, Expression*, source_location);
  void simple_var_decl_or_assignment(const std::string&, source_location,
				     Range_clause*, Type_switch*);
  void function_decl();
  Typed_identifier* receiver();
  Expression* operand(bool may_be_sink);
  Expression* enclosing_var_reference(Named_object*, Named_object*,
				      source_location);
  Expression* composite_lit(Type*, int depth, source_location);
  Expression* function_lit();
  Expression* create_closure(Named_object* function, Enclosing_vars*,
			     source_location);
  Expression* primary_expr(bool may_be_sink, bool may_be_composite_lit,
			   bool* is_type_switch);
  Expression* selector(Expression*, bool* is_type_switch);
  Expression* index(Expression*);
  Expression* call(Expression*);
  Expression* expression(Precedence, bool may_be_sink,
			 bool may_be_composite_lit, bool* is_type_switch);
  bool expression_may_start_here();
  Expression* unary_expr(bool may_be_sink, bool may_be_composite_lit,
			 bool* is_type_switch);
  Expression* qualified_expr(Expression*, source_location);
  Expression* id_to_expression(const std::string&, source_location);
  void statement(const Label*);
  bool statement_may_start_here();
  void labeled_stmt(const std::string&, source_location);
  Expression* simple_stat(bool, bool, Range_clause*, Type_switch*);
  bool simple_stat_may_start_here();
  void statement_list();
  bool statement_list_may_start_here();
  void expression_stat(Expression*);
  void inc_dec_stat(Expression*);
  void assignment(Expression*, Range_clause*);
  void tuple_assignment(Expression_list*, Range_clause*);
  void send();
  void go_or_defer_stat();
  void return_stat();
  void if_stat();
  void switch_stat(const Label*);
  Statement* expr_switch_body(const Label*, Expression*, source_location);
  void expr_case_clause(Case_clauses*, bool* saw_default);
  Expression_list* expr_switch_case(bool*);
  Statement* type_switch_body(const Label*, const Type_switch&,
			      source_location);
  void type_case_clause(Named_object*, Type_case_clauses*, bool* saw_default);
  void type_switch_case(std::vector<Type*>*, bool*);
  void select_stat(const Label*);
  void comm_clause(Select_clauses*, bool* saw_default);
  bool comm_case(bool*, Expression**, Expression**, std::string*, bool*);
  bool send_or_recv_expr(bool*, Expression**, Expression**, std::string*);
  void for_stat(const Label*);
  void for_clause(Expression**, Block**);
  void range_clause_decl(const Typed_identifier_list*, Range_clause*);
  void range_clause_expr(const Expression_list*, Range_clause*);
  void push_break_statement(Statement*, const Label*);
  void push_continue_statement(Statement*, const Label*);
  void pop_break_statement();
  void pop_continue_statement();
  Statement* find_bc_statement(const Bc_stack*, const std::string&);
  void break_stat();
  void continue_stat();
  void goto_stat();
  void package_clause();
  void import_decl();
  void import_spec(void*);

  void reset_iota();
  int iota_value();
  void increment_iota();

  // Skip past an error looking for a semicolon or OP.  Return true if
  // all is well, false if we found EOF.
  bool
  skip_past_error(Operator op);

  // Verify that an expression is not a sink, and return either the
  // expression or an error.
  Expression*
  verify_not_sink(Expression*);

  // Return the statement associated with a label in a Bc_stack, or
  // NULL.
  Statement*
  find_bc_statement(const Bc_stack*, const std::string&) const;

  // The lexer output we are parsing.
  Lex* lex_;
  // The current token.
  Token token_;
  // A token pushed back on the input stream.
  Token unget_token_;
  // Whether unget_token_ is valid.
  bool unget_token_valid_;
  // The code we are generating.
  Gogo* gogo_;
  // A stack of statements for which break may be used.
  Bc_stack* break_stack_;
  // A stack of statements for which continue may be used.
  Bc_stack* continue_stack_;
  // The current iota value.
  int iota_;
  // References from the local function to variables defined in
  // enclosing functions.
  Enclosing_vars enclosing_vars_;
};


#endif // !defined(GO_PARSE_H)