Go patch committed: Handle _ with explicit type

[Ian Lance Taylor]

In Go code like
        var _ T = F()
(in Go, _ is an unnamed variable which can not be referenced) the
compiler should check whether a value with the return type of F() can be
assigned to a variable of type T.  The compiler was not doing this
check--it was just throwing away the type.  This patch fixes the
problem.  Bootstrapped and ran Go testsuite on
x86_64-unknown-linux-gnu.  Committed to mainline.

Ian


diff -r d65e359c1879 go/parse.cc
--- a/go/parse.cc	Fri Jan 20 07:30:55 2012 -0800
+++ b/go/parse.cc	Fri Jan 20 15:26:29 2012 -0800
@@ -1883,10 +1883,23 @@
     {
       if (!type_from_init && init != NULL)
 	{
-	  if (!this->gogo_->in_global_scope())
+	  if (this->gogo_->in_global_scope())
+	    return this->create_dummy_global(type, init, location);
+	  else if (type == NULL)
 	    this->gogo_->add_statement(Statement::make_statement(init, true));
 	  else
-	    return this->create_dummy_global(type, init, location);
+	    {
+	      // With both a type and an initializer, create a dummy
+	      // variable so that we will check whether the
+	      // initializer can be assigned to the type.
+	      Variable* var = new Variable(type, init, false, false, false,
+					   location);
+	      static int count;
+	      char buf[30];
+	      snprintf(buf, sizeof buf, "sink$%d", count);
+	      ++count;
+	      return this->gogo_->add_variable(buf, var);
+	    }
 	}
       return this->gogo_->add_sink();
     }