‘An InputDecorator…cannot have an unbounded width’

The error message suggests that it’s also related to box constraints, 
which are important to understand to avoid many of the most common 
Flutter framework errors.

What does the error look like?

The message shown by the error looks like this:

How might you run into the error?

This error occurs, for example, when a Row contains a TextFormField or a
TextField but the latter has no width constraint.

How to fix it?

As suggested by the error message, fix this error by constraining the text field
using either an Expanded or SizedBox widget. The following example
demonstrates using an Expanded widget:

‘Incorrect use of ParentData widget’

This error is about missing an expected parent widget.

What does the error look like?

The message shown by the error looks like this: