Add support for a named block to only have variable definitions.

It is legal for a named block to contain variable definitions and
no statements. This patch fixes this for both style of blocks. It
also organizes the block parsing code to be a bit more clear, adds
an error case for fork/join and changes on check for size() > 0 for
the more efficient ! empty().

parse.y

@@ -255,7 +255,7 @@ static long check_enum_seq_value(const YYLTYPE&loc, verinum *arg, bool zero_ok)
 
 static void current_task_set_statement(vector<Statement*>*s)
 {
-      assert(s && s->size() > 0);
+      assert(s && !s->empty());
       if (s->size() == 1) {
 	    current_task->set_statement((*s)[0]);
 	    return;
@@ -505,6 +505,7 @@ static void current_task_set_statement(vector<Statement*>*s)
 %type <event_statement> event_control
 %type <statement> statement statement_or_null compressed_statement
 %type <statement_list> statement_list statement_or_null_list
+%type <statement_list> statement_list_or_null
 
 %type <statement> analog_statement
 
@@ -4285,6 +4286,11 @@ statement
      name. These are handled by pushing the scope name, then matching
      the declarations. The scope is popped at the end of the block. */
 
+  | K_begin K_end
+      { PBlock*tmp = new PBlock(PBlock::BL_SEQ);
+	FILE_NAME(tmp, @1);
+	$$ = tmp;
+      }
   | K_begin statement_list K_end
       { PBlock*tmp = new PBlock(PBlock::BL_SEQ);
 	FILE_NAME(tmp, @1);
@@ -4298,27 +4304,16 @@ statement
 	current_block_stack.push(tmp);
       }
     block_item_decls_opt
-    statement_list K_end
+    statement_list_or_null K_end
       { pform_pop_scope();
 	assert(! current_block_stack.empty());
 	PBlock*tmp = current_block_stack.top();
 	current_block_stack.pop();
-	tmp->set_statement(*$6);
+	if ($6) tmp->set_statement(*$6);
 	delete[]$3;
 	delete $6;
 	$$ = tmp;
       }
-  | K_begin K_end
-      { PBlock*tmp = new PBlock(PBlock::BL_SEQ);
-	FILE_NAME(tmp, @1);
-	$$ = tmp;
-      }
-  | K_begin ':' IDENTIFIER K_end
-      { PBlock*tmp = new PBlock(PBlock::BL_SEQ);
-	FILE_NAME(tmp, @1);
-	delete[]$3;
-	$$ = tmp;
-      }
   | K_begin error K_end
       { yyerrok; }
 
@@ -4327,33 +4322,36 @@ statement
      need to do is remember that this is a parallel block so that the
      code generator can do the right thing. */
 
+  | K_fork K_join
+      { PBlock*tmp = new PBlock(PBlock::BL_PAR);
+	FILE_NAME(tmp, @1);
+	$$ = tmp;
+      }
+  | K_fork statement_list K_join
+      { PBlock*tmp = new PBlock(PBlock::BL_PAR);
+	FILE_NAME(tmp, @1);
+	tmp->set_statement(*$2);
+	delete $2;
+	$$ = tmp;
+      }
   | K_fork ':' IDENTIFIER
       { PBlock*tmp = pform_push_block_scope($3, PBlock::BL_PAR);
 	FILE_NAME(tmp, @1);
 	current_block_stack.push(tmp);
       }
     block_item_decls_opt
-    statement_list K_join
+    statement_list_or_null K_join
       { pform_pop_scope();
         assert(! current_block_stack.empty());
 	PBlock*tmp = current_block_stack.top();
 	current_block_stack.pop();
-	tmp->set_statement(*$6);
+	if ($6) tmp->set_statement(*$6);
 	delete[]$3;
 	delete $6;
 	$$ = tmp;
       }
-  | K_fork K_join
+  | K_fork error K_join
-      { PBlock*tmp = new PBlock(PBlock::BL_PAR);
+      { yyerrok; }
-	FILE_NAME(tmp, @1);
-	$$ = tmp;
-      }
-  | K_fork ':' IDENTIFIER K_join
-      { PBlock*tmp = new PBlock(PBlock::BL_PAR);
-	FILE_NAME(tmp, @1);
-	delete[]$3;
-	$$ = tmp;
-      }
 
 	| K_disable hierarchy_identifier ';'
 		{ PDisable*tmp = new PDisable(*$2);
@@ -4372,13 +4370,6 @@ statement
 		  FILE_NAME(tmp, @1);
 		  $$ = tmp;
 		}
-	| K_fork statement_list K_join
-		{ PBlock*tmp = new PBlock(PBlock::BL_PAR);
-		  FILE_NAME(tmp, @1);
-		  tmp->set_statement(*$2);
-		  delete $2;
-		  $$ = tmp;
-		}
 	| K_repeat '(' expression ')' statement
 		{ PRepeat*tmp = new PRepeat($3, $5);
 		  FILE_NAME(tmp, @1);
@@ -4677,6 +4668,21 @@ compressed_statement
 		}
 	;
 
+statement_list_or_null
+  : statement_list_or_null statement
+      { vector<Statement*>*tmp = $1;
+	if (tmp) {
+	      tmp->push_back($2);
+	} else {
+	      tmp = new vector<Statement*>(1);
+	      tmp->at(0) = $2;
+	}
+	$$ = tmp;
+      }
+  |
+      { $$ = 0; }
+  ;
+
 statement_list
   : statement_list statement
       { vector<Statement*>*tmp = $1;