Warn in dev if shouldComponentUpdate is defined on PureComponent

[aweary]

Currently, if you define shouldComponentUpdate on React.PureComponent nothing bad happens and it acts like React.Component https://jsfiddle.net/jekmdfva/

We should probably warn in dev since it defaults the point of PureComponent

[gaearon]

Unrelated, but I also wanted to suggest warning for setting defaultProps and propTypes on instances (I've seen people do this with class properties syntax). Maybe somebody could do all three warnings together?

[aweary]

That's a great idea, happy to help anyone who wants to give this a shot

[misoguy]

I'd like to give this a shot :)

[misoguy]

What kind of warning message should it be? I'm trying to write a test first :)

[misoguy]

After writing a simple test code, I realized that there is a test code to ensure shouldComponentUpdate can be overridden.
What is the expected behavior when it is overridden?

[aweary]

@misoguy I responded to your question in your PR!

[abhaynikam]

@aweary : Issue is open since 23 days. Would like to contribute for same.

[abhaynikam]

Unrelated, but I also wanted to suggest warning for setting defaultProps and propTypes on instances 
(I've seen people do this with class properties syntax). 
Maybe somebody could do all three warnings together?

@gaearon : can you help me understand what is expected behavior here? I can work on adding other two warnings. @misoguy has almost completed with the shouldComponentUpdate warning while extending from PureComponent