title: tidyr enframe vs pivot_longer for named vector
body: <p>For converting a named vector to a 2-column tibble, it seems like <code>pivot_longer()</code> should work the same as <code>enframe()</code> but it doesn't.</p>
  
  <pre><code>names &lt;- c("John", "Steve", "Jim", "Christopher")
  name_chars &lt;- sapply(names, nchar)
  
  name_chars_enf &lt;- enframe(name_chars, name = "Name", value = "Chars")
  
    # A tibble: 4 x 2
    Name        Chars
    &lt;chr&gt;       &lt;int&gt;
  1 John            4
  2 Steve           5
  3 Jim             3
  4 Christopher    11
  
  name_chars_piv_long &lt;- pivot_longer(name_chars, names_to = "Name", values_to = "Chars")
  
  Error in is_call(expr, paren_sym) : 
    argument "expr" is missing, with no default
  </code></pre>
  
  <p>Why doesn't <code>pivot_longer()</code> work this way?</p>