title: pivot_wider issue "Values in `values_from` are not uniquely identified; output will contain list-cols"
body: <p>My data looks like this:</p>
  
  <pre><code># A tibble: 6 x 4
    name          val time          x1
    &lt;chr&gt;       &lt;dbl&gt; &lt;date&gt;     &lt;dbl&gt;
  1 C Farolillo     7 2016-04-20  51.5
  2 C Farolillo     3 2016-04-21  56.3
  3 C Farolillo     7 2016-04-22  56.3
  4 C Farolillo    13 2016-04-23  57.9
  5 C Farolillo     7 2016-04-24  58.7
  6 C Farolillo     9 2016-04-25  59.0
  </code></pre>
  
  <p>I am trying to use the <code>pivot_wider</code> function to expand out the data based on the <code>name</code> column. I use the following code:</p>
  
  <pre><code>yy &lt;- d %&gt;% 
    pivot_wider(., names_from = name, values_from = val)
  </code></pre>
  
  <p>Which gives me the following warning message:</p>
  
  <pre><code>Warning message:
  Values in `val` are not uniquely identified; output will contain list-cols.
  * Use `values_fn = list(val = list)` to suppress this warning.
  * Use `values_fn = list(val = length)` to identify where the duplicates arise
  * Use `values_fn = list(val = summary_fun)` to summarise duplicates
  </code></pre>
  
  <p>The output looks like:</p>
  
  <pre><code>       time       x1        out1    out2 
      2016-04-20  51.50000    &lt;dbl&gt;   &lt;dbl&gt;
  2   2016-04-21  56.34615    &lt;dbl&gt;   &lt;dbl&gt;
  3   2016-04-22  56.30000    &lt;dbl&gt;   &lt;dbl&gt;
  4   2016-04-23  57.85714    &lt;dbl&gt;   &lt;dbl&gt;
  5   2016-04-24  58.70968    &lt;dbl&gt;   &lt;dbl&gt;
  6   2016-04-25  58.96774    &lt;dbl&gt;   &lt;dbl&gt;
  </code></pre>
  
  <p>I know that <a href="https://tidyr.tidyverse.org/articles/pivot.html" rel="noreferrer">here</a> mentions the issue and to resolve it they suggest using summary statistics. However I have time series data and thus do not want to use summary statistics since each day has a single value (and not multiple values).</p>
  
  <p>I know the problem is because the <code>val</code> column has duplicates (i.e. in the above example 7 occurs 3 times.</p>
  
  <p>Any suggestions on how to pivot_wider and overcome this issue?</p>
  
  <p>Data:</p>
  
  <pre><code>    d &lt;- structure(list(name = c("C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", "C Farolillo", 
  "C Farolillo", "C Farolillo", "C Farolillo", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", "Plaza Eliptica", 
  "Plaza Eliptica", "Plaza Eliptica"), val = c(7, 3, 7, 13, 7, 
  9, 20, 19, 4, 5, 5, 2, 6, 6, 16, 13, 7, 6, 3, 3, 6, 10, 5, 3, 
  5, 3, 4, 4, 10, 11, 4, 13, 8, 2, 8, 10, 3, 10, 14, 4, 2, 4, 6, 
  6, 8, 8, 3, 3, 13, 10, 13, 32, 25, 31, 34, 26, 33, 35, 43, 22, 
  22, 21, 10, 33, 33, 48, 47, 27, 23, 11, 13, 25, 31, 20, 16, 10, 
  9, 23, 11, 23, 26, 16, 34, 17, 4, 24, 21, 10, 26, 32, 10, 5, 
  9, 19, 14, 27, 27, 10, 8, 28, 32, 25), time = structure(c(16911, 
  16912, 16913, 16914, 16915, 16916, 16917, 16918, 16919, 16920, 
  16921, 16922, 16923, 16923, 16924, 16925, 16926, 16927, 16928, 
  16929, 16930, 16931, 16932, 16933, 16934, 16935, 16936, 16937, 
  16938, 16939, 16940, 16941, 16942, 16943, 16944, 16945, 16946, 
  16947, 16948, 16949, 16950, 16951, 16952, 16953, 16954, 16955, 
  16956, 16957, 16958, 16959, 16960, 16911, 16912, 16913, 16914, 
  16915, 16916, 16917, 16918, 16919, 16920, 16921, 16922, 16923, 
  16923, 16924, 16925, 16926, 16927, 16928, 16929, 16930, 16931, 
  16932, 16933, 16934, 16935, 16936, 16937, 16938, 16939, 16940, 
  16941, 16942, 16943, 16944, 16945, 16946, 16947, 16948, 16949, 
  16950, 16951, 16952, 16953, 16954, 16955, 16956, 16957, 16958, 
  16959, 16960), class = "Date"), x1 = c(51.5, 56.3461538461538, 
  56.3, 57.8571428571429, 58.7096774193548, 58.9677419354839, 64.4615384615385, 
  61.9310344827586, 60.3214285714286, 59.4137931034483, 59.5806451612903, 
  57.3448275862069, 64.0333333333333, 64.0333333333333, 70.15625, 
  71.3636363636364, 62.8125, 56.4375, 56.4516129032258, 51.741935483871, 
  52.84375, 53.09375, 52.969696969697, 54, 54.3870967741936, 60.3870967741936, 
  64.4516129032258, 66.2903225806452, 68.2333333333333, 69.7741935483871, 
  70.5806451612903, 73.8275862068966, 72.8181818181818, 64.6764705882353, 
  64.4838709677419, 68.7741935483871, 62.1764705882353, 68.969696969697, 
  70.1935483870968, 59.6774193548387, 59.9677419354839, 63.125, 
  67.5882352941177, 71.4705882352941, 73.8529411764706, 76.1935483870968, 
  72.6451612903226, 76.0645161290323, 76.4193548387097, 81.7741935483871, 
  85.0645161290323, 51.5, 56.3461538461538, 56.3, 57.8571428571429, 
  58.7096774193548, 58.9677419354839, 64.4615384615385, 61.9310344827586, 
  60.3214285714286, 59.4137931034483, 59.5806451612903, 57.3448275862069, 
  64.0333333333333, 64.0333333333333, 70.15625, 71.3636363636364, 
  62.8125, 56.4375, 56.4516129032258, 51.741935483871, 52.84375, 
  53.09375, 52.969696969697, 54, 54.3870967741936, 60.3870967741936, 
  64.4516129032258, 66.2903225806452, 68.2333333333333, 69.7741935483871, 
  70.5806451612903, 73.8275862068966, 72.8181818181818, 64.6764705882353, 
  64.4838709677419, 68.7741935483871, 62.1764705882353, 68.969696969697, 
  70.1935483870968, 59.6774193548387, 59.9677419354839, 63.125, 
  67.5882352941177, 71.4705882352941, 73.8529411764706, 76.1935483870968, 
  72.6451612903226, 76.0645161290323, 76.4193548387097, 81.7741935483871, 
  85.0645161290323)), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
  -102L))
  </code></pre>