Improve condition support for Python and Rust

[pokey]

• Adds condition support for Python ternaries
• Adds condition support for Python list comprehensions
• Adds condition support for Python match statements
• Adds condition support for Rust match statements
• Note that "chuck" includes the if keyword for match statements and list comprehensions
• Split from Pattern matching support #831

Checklist

• I have added tests
• I have updated the docs and cheatsheet
• I have not broken the cheatsheet

Co-authored-by: Michael Doronin warrior2031@mail.ru

[auscompgeek]

Seems reasonable. I presume if clauses in Python list comprehensions are treated similarly?

[pokey]

Seems reasonable. I presume if clauses in Python list comprehensions are treated similarly?

Hmm I don't believe that they are. Does make me wonder if it's what we want; feels a bit small for "if state", as it's not a full statement. Ie "state" should be a superset of "if state", and I don't think "state" wants to get trapped this far down

Otoh I do sometimes find myself wanting to target the if in python comprehensions

cc/ @AndreasArvidsson wdyt

[AndreasArvidsson]

I guess it's similar to trying to target a ternary in other languages. I do agree that if statement isn't the best description for any of those, but it probably would be useful to be able to target them.

[pokey]

Discussed in meet-up:

• We'd like to switch this to condition
• For "change" it doesn't include the if keyword
• For "chuck" it does include the if keyword

[pokey]

@purpleP fyi we are now using "condition" instead of "if state" here