Add null-check With Creating a New Variable

[EmreSURK]

Dart is great, and null-safety is great too. It allows developers to eliminate null-related-crashes easily.

I strongly believe we can move forward with syntax.

Currently, developers still need to check the variable if null like that:

var someVariable = data?.someMember;
if ( someVariable != null ) {
     // code..
}

These checks are so similar for non-optional values, so most developers get confused and can not see the beauty of the optional types. Most of the time the someVariable variable is not being used outside of the if block.

I am suggesting null checking while defining a non-optional variable inside if block:

if ( var someVariable = data?.someMember ) {
    // we have someVariable variable, it has data and it is not optional anymore.
} else {
   // we don't have someVariable variable, data or someMember is null. 
}

// someVariable variable is not defined here.

I inspired by other languages, of course.

Let me know what you think.

Best.

[eernstg]

This idea has been considered elsewhere already: #1201, #1210, #1420, so you may wish to contribute to the discussions there. Also, you may be interested in the topic field-promotion in general.

I'll close this issue as a duplicate of those.