Implement Rule M2

[nobugs-hare]

Depends on implementing NODETRACE*/NODEASSERT in node.cpp subproject.

[marcosbracco]

A question, because to really ensure consistency, requires not only expressions to be const but also to not throw.
If an expression inside NODETRACE throws when evaluated, code flow will change depending on trace level. And ensuring that an expression doesn't throw is not as easy and the subset of them that can be verified becomes very small.

So, should [Rule M2] check for state changes only? Or should we check nothrow also?

[marcosbracco]

Maybe we can surround evaluation of expression in a try/catch inside NODETRACE in such a way that exceptions never get thrown out of a NODETRACE.
If evaluation of the condition throws then we can log it, and continue. This way we don't need to worry about evaluation of expression inside NODETRACE throwing.

[nobugs-hare]

IMHO (let's also ask DI if he's ok with it):

• for NODETRACE, let's surround it with try-catch (and NOT check for nothrow)
• for NODEASSERT, let's NOT surround it with try-catch (but DO check for nothrow for any called functions).

If this is ok (and with DI too) - let's proceed in this direction

[marcosbracco]

@divanchykhin do you have any comments on this?