This was previously fixed many versions ago, but must have crept back in somewhere:

• ZBX-3606
• ZBX-3050
• ZBX-1915
• etc...

Steps to reproduce:

Scenario 1 - 

1. Create a host 'AAA'
2. Create a template 'AAA'

Scenario 2 - 

1. Create a template 'AAA'
2. Create a host 'AAA'

Result:

Scenario 1 - Error Message

'Template with the same name "AAA" already exists.'

Scenario 2 - Error Message when creating template with same name as template.

'Host with the same name "AAA" already exists.'

Expected:
You should be able to create a host with the same name as a template

You should be able to create a template with the same name as a host