title: The named parameter 'child' isn't defined. Try correcting the name to an existing named parameter's name
body: <p>I have a simple dialog widget, it works fine with no errors on windows on beta channel, but when I pull the same repo on a MacBook I end with an error. Both environments are on beta channel</p>
  <blockquote>
  <p>The named parameter 'child' isn't defined.  Try correcting the name
  to an existing named parameter's name, or defining a named parameter
  with the name 'child'</p>
  </blockquote>
  <p>my dialog. what could be causing the child to complain <code>child: new AlertDialog(</code>?</p>
  <pre><code>void _showDialog(
        BuildContext context, QRViewController controller, String result) async {
      await showDialog&lt;String&gt;(
        context: context,
        // FIXME: child isn't defined for this function. need to use right params
          child: new AlertDialog(
          contentPadding: const EdgeInsets.all(16.0),
          content: Container(
            height: 400,
            child: Column(
              children: [
                new Row(
                  children: [
                    Text(
                      'Please record your body temperature \nin Celsius from the digital reading \non the infrared thermometer',
                    ),
                  ],
                ),
                new Row(
                  children: &lt;Widget&gt;[
                    new Expanded(
                      child: new TextField(
                        autofocus: true,
                        onChanged: (value) {
                          temp = value;
                        },
                        decoration: new InputDecoration(hintText: 'C'),
                        keyboardType: TextInputType.number,
                        inputFormatters: &lt;TextInputFormatter&gt;[
                          FilteringTextInputFormatter.allow(
                              RegExp(r'^\d+\.?\d*')),
                        ],
                      ),
                    )
                  ],
                ),
                Row(
                  children: [
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Image.asset(&quot;assets/images/temp_checkin.jpg&quot;,
                          height: 250, fit: BoxFit.scaleDown),
                    ),
                  ],
                )
              ],
            ),
          ),
          actions: &lt;Widget&gt;[
            new FlatButton(
                child: const Text('CANCEL'),
                onPressed: () {
                  _QRViewExampleState.capturedQRCode = false;
                  Navigator.pop(context);
                }),
            new FlatButton(
                child: const Text('SUBMIT'),
                onPressed: () {
                  Navigator.pop(context);
                  if (temp != '' &amp;&amp; temp != null) {
                    _temperatureCheckIn(result, temp, context);
                  }
                  _QRViewExampleState.capturedQRCode = false;
                })
          ],
        ),
      );
    }
  </code></pre>