Change c <- v from an expression to a statement.

Don't do anything special if we don't use the value of <-c.
Fix sending an untyped constant in a select statement.

From-SVN: r171371

7 files changed, 171 insertions, 204 deletions

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 8660c75..125715b 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -12357,103 +12357,6 @@ Expression::make_receive(Expression* channel, source_location location)
   return new Receive_expression(channel, location);
 }
 
-// Class Send_expression.
-
-// Traversal.
-
-int
-Send_expression::do_traverse(Traverse* traverse)
-{
-  if (Expression::traverse(&this->channel_, traverse) == TRAVERSE_EXIT)
-    return TRAVERSE_EXIT;
-  return Expression::traverse(&this->val_, traverse);
-}
-
-// Get the type.
-
-Type*
-Send_expression::do_type()
-{
-  if (this->is_value_discarded_)
-    return Type::make_void_type();
-  else
-    return Type::lookup_bool_type();
-}
-
-// Set types.
-
-void
-Send_expression::do_determine_type(const Type_context*)
-{
-  this->channel_->determine_type_no_context();
-
-  Type* type = this->channel_->type();
-  Type_context subcontext;
-  if (type->channel_type() != NULL)
-    subcontext.type = type->channel_type()->element_type();
-  this->val_->determine_type(&subcontext);
-}
-
-// Check types.
-
-void
-Send_expression::do_check_types(Gogo*)
-{
-  Type* type = this->channel_->type();
-  if (type->is_error_type())
-    {
-      this->set_is_error();
-      return;
-    }
-  Channel_type* channel_type = type->channel_type();
-  if (channel_type == NULL)
-    {
-      error_at(this->location(), "left operand of %<<-%> must be channel");
-      this->set_is_error();
-      return;
-    }
-  Type* element_type = channel_type->element_type();
-  if (element_type != NULL
-      && !Type::are_assignable(element_type, this->val_->type(), NULL))
-    {
-      this->report_error(_("incompatible types in send"));
-      return;
-    }
-  if (!channel_type->may_send())
-    {
-      this->report_error(_("invalid send on receive-only channel"));
-      return;
-    }
-}
-
-// Get a tree for a send expression.
-
-tree
-Send_expression::do_get_tree(Translate_context* context)
-{
-  tree channel = this->channel_->get_tree(context);
-  tree val = this->val_->get_tree(context);
-  if (channel == error_mark_node || val == error_mark_node)
-    return error_mark_node;
-  Channel_type* channel_type = this->channel_->type()->channel_type();
-  val = Expression::convert_for_assignment(context,
-					   channel_type->element_type(),
-					   this->val_->type(),
-					   val,
-					   this->location());
-  return Gogo::send_on_channel(channel, val, this->is_value_discarded_,
-			       this->for_select_, this->location());
-}
-
-// Make a send expression
-
-Send_expression*
-Expression::make_send(Expression* channel, Expression* val,
-		      source_location location)
-{
-  return new Send_expression(channel, val, location);
-}
-
 // An expression which evaluates to a pointer to the type descriptor
 // of a type.
 
diff --git a/gcc/go/gofrontend/expressions.h b/gcc/go/gofrontend/expressions.h
index 1dc408d..fa240a6 100644
--- a/gcc/go/gofrontend/expressions.h
+++ b/gcc/go/gofrontend/expressions.h
@@ -36,7 +36,6 @@ class Field_reference_expression;
 class Interface_field_reference_expression;
 class Type_guard_expression;
 class Receive_expression;
-class Send_expression;
 class Named_object;
 class Export;
 class Import;
@@ -89,7 +88,6 @@ class Expression
     EXPRESSION_COMPOSITE_LITERAL,
     EXPRESSION_HEAP_COMPOSITE,
     EXPRESSION_RECEIVE,
-    EXPRESSION_SEND,
     EXPRESSION_TYPE_DESCRIPTOR,
     EXPRESSION_TYPE_INFO,
     EXPRESSION_STRUCT_FIELD_OFFSET,
@@ -271,10 +269,6 @@ class Expression
   static Receive_expression*
   make_receive(Expression* channel, source_location);
 
-  // Make a send expression.
-  static Send_expression*
-  make_send(Expression* channel, Expression* val, source_location);
-
   // Make an expression which evaluates to the type descriptor of a
   // type.
   static Expression*
@@ -356,8 +350,7 @@ class Expression
 
   // This is called by the parser if the value of this expression is
   // being discarded.  This issues warnings about computed values
-  // being unused, and handles send expressions which act differently
-  // depending upon whether the value is used.
+  // being unused.
   void
   discarding_value()
   { this->do_discarding_value(); }
@@ -1807,7 +1800,7 @@ class Receive_expression : public Expression
  public:
   Receive_expression(Expression* channel, source_location location)
     : Expression(EXPRESSION_RECEIVE, location),
-      channel_(channel), is_value_discarded_(false), for_select_(false)
+      channel_(channel), for_select_(false)
   { }
 
   // Return the channel.
@@ -1827,7 +1820,7 @@ class Receive_expression : public Expression
 
   void
   do_discarding_value()
-  { this->is_value_discarded_ = true; }
+  { }
 
   Type*
   do_type();
@@ -1855,67 +1848,6 @@ class Receive_expression : public Expression
  private:
   // The channel from which we are receiving.
   Expression* channel_;
-  // Whether the value is being discarded.
-  bool is_value_discarded_;
-  // Whether this is for a select statement.
-  bool for_select_;
-};
-
-// A send expression.
-
-class Send_expression : public Expression
-{
- public:
-  Send_expression(Expression* channel, Expression* val,
-		  source_location location)
-    : Expression(EXPRESSION_SEND, location),
-      channel_(channel), val_(val), is_value_discarded_(false),
-      for_select_(false)
-  { }
-
-  // Note that this is for a select statement.
-  void
-  set_for_select()
-  { this->for_select_ = true; }
-
- protected:
-  int
-  do_traverse(Traverse* traverse);
-
-  void
-  do_discarding_value()
-  { this->is_value_discarded_ = true; }
-
-  Type*
-  do_type();
-
-  void
-  do_determine_type(const Type_context*);
-
-  void
-  do_check_types(Gogo*);
-
-  Expression*
-  do_copy()
-  {
-    return Expression::make_send(this->channel_->copy(), this->val_->copy(),
-				 this->location());
-  }
-
-  bool
-  do_must_eval_in_order() const
-  { return true; }
-
-  tree
-  do_get_tree(Translate_context*);
-
- private:
-  // The channel on which to send the value.
-  Expression* channel_;
-  // The value to send.
-  Expression* val_;
-  // Whether the value is being discarded.
-  bool is_value_discarded_;
   // Whether this is for a select statement.
   bool for_select_;
 };
diff --git a/gcc/go/gofrontend/gogo.cc b/gcc/go/gofrontend/gogo.cc
index f8c143c..f2476d5 100644
--- a/gcc/go/gofrontend/gogo.cc
+++ b/gcc/go/gofrontend/gogo.cc
@@ -1926,14 +1926,6 @@ Order_eval::statement(Block* block, size_t* pindex, Statement* s)
     {
       Expression** pexpr = *p;
 
-      // If the last expression is a send or receive expression, we
-      // may be ignoring the value; we don't want to evaluate it
-      // early.
-      if (p + 1 == find_eval_ordering.end()
-	  && ((*pexpr)->classification() == Expression::EXPRESSION_SEND
-	      || (*pexpr)->classification() == Expression::EXPRESSION_RECEIVE))
-	break;
-
       // The last expression in a thunk will be the call passed to go
       // or defer, which we must not evaluate early.
       if (is_thunk && p + 1 == find_eval_ordering.end())
diff --git a/gcc/go/gofrontend/parse.cc b/gcc/go/gofrontend/parse.cc
index 7c03870..2e59149 100644
--- a/gcc/go/gofrontend/parse.cc
+++ b/gcc/go/gofrontend/parse.cc
@@ -2944,9 +2944,6 @@ Parse::expression(Precedence precedence, bool may_be_sink,
 	case OPERATOR_ANDAND:
 	  right_precedence = PRECEDENCE_ANDAND;
 	  break;
-	case OPERATOR_CHANOP:
-	  right_precedence = PRECEDENCE_CHANOP;
-	  break;
 	case OPERATOR_EQEQ:
 	case OPERATOR_NOTEQ:
 	case OPERATOR_LT:
@@ -2997,10 +2994,7 @@ Parse::expression(Precedence precedence, bool may_be_sink,
       Expression* right = this->expression(right_precedence, false,
 					   may_be_composite_lit,
 					   NULL);
-      if (op == OPERATOR_CHANOP)
-	left = Expression::make_send(left, right, binop_location);
-      else
-	left = Expression::make_binary(op, left, right, binop_location);
+      left = Expression::make_binary(op, left, right, binop_location);
     }
 }
 
@@ -3302,8 +3296,10 @@ Parse::labeled_stmt(const std::string& label_name, source_location location)
   this->statement(label);
 }
 
-// SimpleStat =
-//   ExpressionStat | IncDecStat | Assignment | SimpleVarDecl .
+// SimpleStmt = EmptyStmt | ExpressionStmt | SendStmt | IncDecStmt |
+//	Assignment | ShortVarDecl .
+
+// EmptyStmt was handled in Parse::statement.
 
 // In order to make this work for if and switch statements, if
 // RETURN_EXP is true, and we see an ExpressionStat, we return the
@@ -3360,7 +3356,10 @@ Parse::simple_stat(bool may_be_composite_lit, bool return_exp,
       return NULL;
     }
   token = this->peek_token();
-  if (token->is_op(OPERATOR_PLUSPLUS) || token->is_op(OPERATOR_MINUSMINUS))
+  if (token->is_op(OPERATOR_CHANOP))
+    this->send_stmt(this->verify_not_sink(exp));
+  else if (token->is_op(OPERATOR_PLUSPLUS)
+	   || token->is_op(OPERATOR_MINUSMINUS))
     this->inc_dec_stat(this->verify_not_sink(exp));
   else if (token->is_op(OPERATOR_COMMA)
 	   || token->is_op(OPERATOR_EQ))
@@ -3430,6 +3429,20 @@ Parse::expression_stat(Expression* exp)
   this->gogo_->add_statement(Statement::make_statement(exp));
 }
 
+// SendStmt = Channel "&lt;-" Expression .
+// Channel  = Expression .
+
+void
+Parse::send_stmt(Expression* channel)
+{
+  gcc_assert(this->peek_token()->is_op(OPERATOR_CHANOP));
+  source_location loc = this->location();
+  this->advance_token();
+  Expression* val = this->expression(PRECEDENCE_NORMAL, false, true, NULL);
+  Statement* s = Statement::make_send_statement(channel, val, loc);
+  this->gogo_->add_statement(s);
+}
+
 // IncDecStat = Expression ( "++" | "--" ) .
 
 void
@@ -4159,7 +4172,7 @@ Parse::select_stat(const Label* label)
   this->gogo_->add_statement(statement);
 }
 
-// CommClause = CommCase [ StatementList ] .
+// CommClause = CommCase ":" { Statement ";" } .
 
 void
 Parse::comm_clause(Select_clauses* clauses, bool* saw_default)
@@ -4173,6 +4186,11 @@ Parse::comm_clause(Select_clauses* clauses, bool* saw_default)
   bool got_case = this->comm_case(&is_send, &channel, &val, &varname,
 				  &is_default);
 
+  if (this->peek_token()->is_op(OPERATOR_COLON))
+    this->advance_token();
+  else
+    error_at(this->location(), "expected colon");
+
   Block* statements = NULL;
   Named_object* var = NULL;
   if (this->peek_token()->is_op(OPERATOR_SEMICOLON))
@@ -4214,7 +4232,7 @@ Parse::comm_clause(Select_clauses* clauses, bool* saw_default)
     }
 }
 
-// CommCase = ( "default" | ( "case" ( SendExpr | RecvExpr) ) ) ":" .
+// CommCase   = "case" ( SendStmt | RecvStmt ) | "default" .
 
 bool
 Parse::comm_case(bool* is_send, Expression** channel, Expression** val,
@@ -4240,18 +4258,9 @@ Parse::comm_case(bool* is_send, Expression** channel, Expression** val,
       return false;
     }
 
-  if (!this->peek_token()->is_op(OPERATOR_COLON))
-    {
-      error_at(this->location(), "expected colon");
-      return false;
-    }
-
-  this->advance_token();
-
   return true;
 }
 
-// SendExpr = Expression "<-" Expression .
 // RecvExpr =  [ Expression ( "=" | ":=" ) ] "<-" Expression .
 
 bool
@@ -4291,7 +4300,7 @@ Parse::send_or_recv_expr(bool* is_send, Expression** channel, Expression** val,
     }
   else
     {
-      Expression* left = this->expression(PRECEDENCE_CHANOP, true, true, NULL);
+      Expression* left = this->expression(PRECEDENCE_NORMAL, true, true, NULL);
 
       if (this->peek_token()->is_op(OPERATOR_EQ))
 	{
diff --git a/gcc/go/gofrontend/parse.h b/gcc/go/gofrontend/parse.h
index 6f2ac64..04ae324 100644
--- a/gcc/go/gofrontend/parse.h
+++ b/gcc/go/gofrontend/parse.h
@@ -44,7 +44,6 @@ class Parse
     PRECEDENCE_NORMAL = 0,
     PRECEDENCE_OROR,
     PRECEDENCE_ANDAND,
-    PRECEDENCE_CHANOP,
     PRECEDENCE_RELOP,
     PRECEDENCE_ADDOP,
     PRECEDENCE_MULOP
@@ -229,6 +228,7 @@ class Parse
   void statement_list();
   bool statement_list_may_start_here();
   void expression_stat(Expression*);
+  void send_stmt(Expression*);
   void inc_dec_stat(Expression*);
   void assignment(Expression*, Range_clause*);
   void tuple_assignment(Expression_list*, Range_clause*);
diff --git a/gcc/go/gofrontend/statements.cc b/gcc/go/gofrontend/statements.cc
index c443519..5a4ad06 100644
--- a/gcc/go/gofrontend/statements.cc
+++ b/gcc/go/gofrontend/statements.cc
@@ -3987,6 +3987,90 @@ Statement::make_type_switch_statement(Named_object* var, Expression* expr,
   return new Type_switch_statement(var, expr, location);
 }
 
+// Class Send_statement.
+
+// Traversal.
+
+int
+Send_statement::do_traverse(Traverse* traverse)
+{
+  if (this->traverse_expression(traverse, &this->channel_) == TRAVERSE_EXIT)
+    return TRAVERSE_EXIT;
+  return this->traverse_expression(traverse, &this->val_);
+}
+
+// Determine types.
+
+void
+Send_statement::do_determine_types()
+{
+  this->channel_->determine_type_no_context();
+  Type* type = this->channel_->type();
+  Type_context context;
+  if (type->channel_type() != NULL)
+    context.type = type->channel_type()->element_type();
+  this->val_->determine_type(&context);
+}
+
+// Check types.
+
+void
+Send_statement::do_check_types(Gogo*)
+{
+  Type* type = this->channel_->type();
+  if (type->is_error_type())
+    {
+      this->set_is_error();
+      return;
+    }
+  Channel_type* channel_type = type->channel_type();
+  if (channel_type == NULL)
+    {
+      error_at(this->location(), "left operand of %<<-%> must be channel");
+      this->set_is_error();
+      return;
+    }
+  Type* element_type = channel_type->element_type();
+  if (!Type::are_assignable(element_type, this->val_->type(), NULL))
+    {
+      this->report_error(_("incompatible types in send"));
+      return;
+    }
+  if (!channel_type->may_send())
+    {
+      this->report_error(_("invalid send on receive-only channel"));
+      return;
+    }
+}
+
+// Get a tree for a send statement.
+
+tree
+Send_statement::do_get_tree(Translate_context* context)
+{
+  tree channel = this->channel_->get_tree(context);
+  tree val = this->val_->get_tree(context);
+  if (channel == error_mark_node || val == error_mark_node)
+    return error_mark_node;
+  Channel_type* channel_type = this->channel_->type()->channel_type();
+  val = Expression::convert_for_assignment(context,
+					   channel_type->element_type(),
+					   this->val_->type(),
+					   val,
+					   this->location());
+  return Gogo::send_on_channel(channel, val, true, this->for_select_,
+			       this->location());
+}
+
+// Make a send statement.
+
+Send_statement*
+Statement::make_send_statement(Expression* channel, Expression* val,
+			       source_location location)
+{
+  return new Send_statement(channel, val, location);
+}
+
 // Class Select_clauses::Select_clause.
 
 // Traversal.
@@ -4043,7 +4127,7 @@ Select_clauses::Select_clause::lower(Block* b)
   // If this is a send clause, evaluate the value to send before the
   // select statement.
   Temporary_statement* val_temp = NULL;
-  if (this->is_send_)
+  if (this->is_send_ && !this->val_->is_constant())
     {
       val_temp = Statement::make_temporary(NULL, this->val_, loc);
       b->add_statement(val_temp);
@@ -4054,11 +4138,14 @@ Select_clauses::Select_clause::lower(Block* b)
   Expression* ref = Expression::make_temporary_reference(channel_temp, loc);
   if (this->is_send_)
     {
-      Expression* ref2 = Expression::make_temporary_reference(val_temp, loc);
-      Send_expression* send = Expression::make_send(ref, ref2, loc);
-      send->discarding_value();
+      Expression* ref2;
+      if (val_temp == NULL)
+	ref2 = this->val_;
+      else
+	ref2 = Expression::make_temporary_reference(val_temp, loc);
+      Send_statement* send = Statement::make_send_statement(ref, ref2, loc);
       send->set_for_select();
-      init->add_statement(Statement::make_statement(send));
+      init->add_statement(send);
     }
   else
     {
diff --git a/gcc/go/gofrontend/statements.h b/gcc/go/gofrontend/statements.h
index 80cdffe..83d5436 100644
--- a/gcc/go/gofrontend/statements.h
+++ b/gcc/go/gofrontend/statements.h
@@ -23,6 +23,7 @@ class For_statement;
 class For_range_statement;
 class Switch_statement;
 class Type_switch_statement;
+class Send_statement;
 class Select_statement;
 class Variable;
 class Named_object;
@@ -99,6 +100,7 @@ class Statement
     STATEMENT_UNNAMED_LABEL,
     STATEMENT_IF,
     STATEMENT_CONSTANT_SWITCH,
+    STATEMENT_SEND,
     STATEMENT_SELECT,
 
     // These statements types are created by the parser, but they
@@ -236,6 +238,10 @@ class Statement
   static Type_switch_statement*
   make_type_switch_statement(Named_object* var, Expression*, source_location);
 
+  // Make a send statement.
+  static Send_statement*
+  make_send_statement(Expression* channel, Expression* val, source_location);
+
   // Make a select statement.
   static Select_statement*
   make_select_statement(source_location);
@@ -592,6 +598,44 @@ class Return_statement : public Statement
   Expression_list* vals_;
 };
 
+// A send statement.
+
+class Send_statement : public Statement
+{
+ public:
+  Send_statement(Expression* channel, Expression* val,
+		 source_location location)
+    : Statement(STATEMENT_SEND, location),
+      channel_(channel), val_(val), for_select_(false)
+  { }
+
+  // Note that this is for a select statement.
+  void
+  set_for_select()
+  { this->for_select_ = true; }
+
+ protected:
+  int
+  do_traverse(Traverse* traverse);
+
+  void
+  do_determine_types();
+
+  void
+  do_check_types(Gogo*);
+
+  tree
+  do_get_tree(Translate_context*);
+
+ private:
+  // The channel on which to send the value.
+  Expression* channel_;
+  // The value to send.
+  Expression* val_;
+  // Whether this is for a select statement.
+  bool for_select_;
+};
+
 // Select_clauses holds the clauses of a select statement.  This is
 // built by the parser.