Add support for exception analysis. about reanalyze

[cristianoc]

Thank you for bringing up this issue, and for our conversation about it.

Here are some preliminary notes for a possible design.
The goal is to guide the user towards progressively replacing exceptions by other mechanisms, such as option or result types.
In truly exceptional circumstances, you would want to just add annotations to acknowledge intentional uses of exceptions and what areas of code are affected by them.
If you use exceptions extensively, and want to continue doing so, this analysis won't be helpful.

Some design thoughts:

• You need to opt into exception checking.
• Any function that throws exceptions gives a warning.
• An annotation is supported to acknowledge that the function throws (those) exceptions.
• Even when a function is annotated, any user of that function that does not catch the exceptions will get a waring. Unless the user itself is annotated, and so on.
• Enough knowledge needs to be made available somehow of what library functions throw what exceptions.

[cristianoc]

To test the ideas quickly, one could build an extremely simplified prototype that:

• Operates at the level of individual value definitions, disregarding nesting.
• Does not distinguish between kinds of exceptions.
• Only checks if there is some occurrence of an exception-catching mechanism.

That rough first experiment would be very imprecise, but could give a feel for the process to follow when using such an analysis. Before the full analysis is built.

[cristianoc]

Progress here #29
And here #32

[cristianoc]

#34

[cristianoc]

#35

[cristianoc]

@sgrove this is the first full-featured iteration, except it can't read annotations across files.
So if an annotation is added to A.re, and B.re uses A.re, then B.re will not see any annotations from A.

[cristianoc]

#36

[cristianoc]

#37

[cristianoc]

#38

[cristianoc]

e2a82b0

[cristianoc]

#39

[cristianoc]

A feature-complete version is in release 1.8.0
https://github.com/cristianoc/reanalyze/releases/tag/v1.8.0