UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Steps to reproduce the problem:
1. let a = aaa(); // Reference error: 'aaa' is not defined
2. let a = 1; // Syntax error: identifier 'a' has already been declared
3. a = 1; // Reference error: a is not defined

What is the expected behavior?
 Line 2 should be successful since the initializer of line 1 is invalid. Or line 3 should be successful since line 2 stated that identifier 'a' has already been declared.

What went wrong?
Line 1 failed is correct, since aaa() does not exist. However line 2 indicate the variable 'a' has been created disregard line 1 failed. Now, line 3 is in contradiction with line 2. Dead lock for variable 'a'.

Did this work before? N/A 

Chrome version: 63.0.3239.132  Channel: stable
OS Version: 10.0
Flash Version: 

This work as expected in Edge (line 2 work as expected).