TYPO3 Core

typo3_src/vendor/typo3fluid/fluid/src/View/TemplatePaths.php Line 588 seems not to reachable.

Reproduce:
1. set templateRootPaths.0 to another location with a typo in the path name
2. open the page where the template should be rendered.

Default template is used instead of displaying an error message

In my case I had tx_hairu and configured fileadmin/Resources/Private/hairu/Templates/ via constants
The path to the templates was fileadmin/Resources/Private/hairu/Template/ (missing s)

The following line seems to always add the default path to the configured path
$paths[$name] = array_merge($defaultPaths, (array)$configuredPaths[$name]);

this line in 8.5.1
$paths[$name] = (array)$configuredPaths[$name] + $defaultPaths;

So in the end the default template was used to render the LoginForm.

I would think that, this is not the desired behaviour.