// Push a new scope to contain the variable and shadow any variable
// with the same name.
expressionContext.pushBlockScope();
// Push a new position scope to track the iteration position
expressionContext.pushPositionScope();
PositionScope pc = expressionContext.getPositionScope();
// Declare an unitialized variable.
InternalExpressionScope scope = (InternalExpressionScope)
expressionContext.getCurrentScope();