From 05d556e8371b90c5de4175aa737a7ad83726eeee Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Tue, 14 Dec 2010 05:54:33 +0000
Subject: [PATCH] Don't incorrectly parse expression as type switch.

Improve error reporting of invalid type assertions.

From-SVN: r167787
---
 gcc/go/gofrontend/expressions.cc | 25 +++++++++++++++----------
 gcc/go/gofrontend/parse.cc       | 17 +++++++++++------
 gcc/go/gofrontend/statements.cc  |  3 ++-
 3 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 022f5ce..6320f09 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -11620,24 +11620,29 @@ Type_guard_expression::do_check_types(Gogo*)
 	this->report_error(_("invalid unsafe.Pointer conversion"));
     }
   else if (expr_type->interface_type() == NULL)
-    this->report_error(_("type assertion only valid for interface types"));
+    {
+      if (!expr_type->is_error_type() && !this->type_->is_error_type())
+	this->report_error(_("type assertion only valid for interface types"));
+      this->set_is_error();
+    }
   else if (this->type_->interface_type() == NULL)
     {
       std::string reason;
       if (!expr_type->interface_type()->implements_interface(this->type_,
 							     &reason))
 	{
-	  if (reason.empty())
-	    this->report_error(_("impossible type assertion: "
-				 "type does not implement interface"));
-	  else
+	  if (!this->type_->is_error_type())
 	    {
-	      error_at(this->location(),
-		       ("impossible type assertion: "
-			"type does not implement interface (%s)"),
-		       reason.c_str());
-	      this->set_is_error();
+	      if (reason.empty())
+		this->report_error(_("impossible type assertion: "
+				     "type does not implement interface"));
+	      else
+		error_at(this->location(),
+			 ("impossible type assertion: "
+			  "type does not implement interface (%s)"),
+			 reason.c_str());
 	    }
+	  this->set_is_error();
 	}
     }
 }
diff --git a/gcc/go/gofrontend/parse.cc b/gcc/go/gofrontend/parse.cc
index c8b55c5..5f4cef5 100644
--- a/gcc/go/gofrontend/parse.cc
+++ b/gcc/go/gofrontend/parse.cc
@@ -2647,12 +2647,18 @@ Parse::selector(Expression* left, bool* is_type_switch)
     {
       this->advance_token();
       Type* type = NULL;
-      if (is_type_switch == NULL
-	  || !this->peek_token()->is_keyword(KEYWORD_TYPE))
+      if (!this->peek_token()->is_keyword(KEYWORD_TYPE))
 	type = this->type();
       else
 	{
-	  *is_type_switch = true;
+	  if (is_type_switch != NULL)
+	    *is_type_switch = true;
+	  else
+	    {
+	      error_at(this->location(),
+		       "use of %<.(type)%> outside type switch");
+	      type = Type::make_error_type();
+	    }
 	  this->advance_token();
 	}
       if (!this->peek_token()->is_op(OPERATOR_RPAREN))
@@ -2866,7 +2872,7 @@ Parse::expression(Precedence precedence, bool may_be_sink,
       left = this->verify_not_sink(left);
       Expression* right = this->expression(right_precedence, false,
 					   may_be_composite_lit,
-					   is_type_switch);
+					   NULL);
       if (op == OPERATOR_CHANOP)
 	left = Expression::make_send(left, right, binop_location);
       else
@@ -2959,8 +2965,7 @@ Parse::unary_expr(bool may_be_sink, bool may_be_composite_lit,
 	  return Expression::make_type(this->type(), location);
 	}
 
-      Expression* expr = this->unary_expr(false, may_be_composite_lit,
-					  is_type_switch);
+      Expression* expr = this->unary_expr(false, may_be_composite_lit, NULL);
       if (expr->is_error_expression())
 	;
       else if (op == OPERATOR_MULT && expr->is_type_expression())
diff --git a/gcc/go/gofrontend/statements.cc b/gcc/go/gofrontend/statements.cc
index 10fe7e4..2d17797 100644
--- a/gcc/go/gofrontend/statements.cc
+++ b/gcc/go/gofrontend/statements.cc
@@ -1296,7 +1296,8 @@ Tuple_type_guard_assignment_statement::do_lower(Gogo*, Block* enclosing)
   Type* expr_type = this->expr_->type();
   if (expr_type->interface_type() == NULL)
     {
-      this->report_error(_("type assertion only valid for interface types"));
+      if (!expr_type->is_error_type() && !this->type_->is_error_type())
+	this->report_error(_("type assertion only valid for interface types"));
       return Statement::make_error_statement(loc);
     }
 
-- 
2.7.4