Running "composer update" leads to errors with coder ...
&gt; Drupal\Core\Composer\Composer::vendorTestCodeCleanup
  - Updating drupal/coder (8.2.12 =&gt; 8.3.1)    The package has modified files:
    D coder_sniffer/Drupal/Test/Array/ArrayUnitTest.inc
    D coder_sniffer/Drupal/Test/Array/ArrayUnitTest.inc.fixed
    D coder_sniffer/Drupal/Test/Array/ArrayUnitTest.php
    D coder_sniffer/Drupal/Test/Array/DisallowLongArraySyntaxUnitTest.php
    D coder_sniffer/Drupal/Test/Array/disallow_long_array_d7/DisallowLongArraySyntaxUnitTest.1.inc
    D coder_sniffer/Drupal/Test/Array/disallow_long_array_d7/disallow_long_array_d7.info
    D coder_sniffer/Drupal/Test/Array/disallow_long_array_d8/DisallowLongArraySyntaxUnitTest.2.inc
    D coder_sniffer/Drupal/Test/Array/disallow_long_array_d8/DisallowLongArraySyntaxUnitTest.2.inc.fixed
    D coder_sniffer/Drupal/Test/Array/disallow_long_array_d8/disallow_long_array_d8.info.yml
    D coder_sniffer/Drupal/Test/Classes/ClassCreateInstanceUnitTest.inc


  [ErrorException]                 
  A non-numeric value encountered  


I have tried with errors

$ composer require drupal/coder ^8.3  
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - The requested package symfony/debug (locked at v4.1.7, required as ^3.4.0) is satisfiable by symfony/debug[v4.1.7] but these conflict with your requirements or minimum-stability.
  Problem 2
    - Conclusion: remove doctrine/annotations v1.6.0
    - Conclusion: don't install doctrine/annotations v1.6.0
    - Can only install one of: doctrine/annotations[v1.2.0, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.1, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.2, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.3, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.4, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.5, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.6, v1.6.0].
    - Can only install one of: doctrine/annotations[v1.2.7, v1.6.0].
    - Installation request for doctrine/annotations (locked at v1.6.0, required as ^1.2) -&gt; satisfiable by doctrine/annotations[v1.6.0].
    - Installation request for doctrine/annotations 1.2.* -&gt; satisfiable by doctrine/annotations[v1.2.0, v1.2.1, v1.2.2, v1.2.3, v1.2.4, v1.2.5, v1.2.6, v1.2.7].


Installation failed, reverting ./composer.json to its original content.


Also tried with errors

rm vendor/ -rf 
composer update
....
Writing lock file
Generating autoload files
&gt; Drupal\Core\Composer\Composer::preAutoloadDump
&gt; Drupal\Core\Composer\Composer::ensureHtaccess
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - The requested package doctrine/annotations 1.2.* exists as doctrine/annotations[v1.6.0] but these are rejected by your constraint.


but always end up with other errors 
Any thoughts ?
What worked is the following commands

rm composer.lock
rm vendor -rf
composer clear-cache
composer require --dev drupal/coder
composer update


with last command perhaps not needed as the previous composer command does an implicit update