Ternary expressions

[JSAbrahams]

Relevant issues

Closes #164 Should've been a separate issue but couldn't be bothered to create one.

Introduced bug highlighted in #366 . Discovered bug highlighted in #367

Summary

Treat if expressions as expressions where relevant by converting them to python ternary expressions.

• Remove ExpressionAny, which introduced a lot of unnecessary logic and complexity. Streamlining of logic made it easier to implement this new feature. Instead, just have a dedicated Any type and match this if needed. (Perhaps this introduced the bug in #366?).

Added Tests

• Happy assign propagated into if
• Happy ... and match
• Happy If converted to ternary when used as function argument

[JSAbrahams]

Hm what about functions which have code blocks as a body but which should be treated as an expression. I.e.:

def my_var := if cond then
    print("then")
    10
else
    print("else")
    20

This should then become the following python code:

if cond then
    print("then")
    my_var = 10
else
    print("else")
    my_var = 20

[JSAbrahams]

Before merging, it'd be nice actually to check other situations where an if expression should be converted to a Python ternary expression. Currently, we only do this within a function argument. What about using an (inline-)if expressions for:

• Variable declarations
• Nested further within other if's
• Used as a condition for an if, match
• Used in any other location as an expression, e.g. a for loop condition

I suspect it will work in these situations as well (and it should, we want to be as generic as possible here!). But alas the project has reached a level of complexity where I can't accurately predict if it will, so we must test.

[codecov[bot]]

Codecov Report

Merging #364 (b52c7e1) into develop (b12963b) will increase coverage by 0.06%. The diff coverage is 92.01%.

@@             Coverage Diff             @@
##           develop     #364      +/-   ##
===========================================
+ Coverage    86.99%   87.06%   +0.06%     
===========================================
  Files          108      108              
  Lines        11727    11965     +238     
===========================================
+ Hits         10202    10417     +215     
- Misses        1525     1548      +23     

[JSAbrahams]

Looking at codecov, few notes:

• Coverage drops because we have a lot if where the else block is a panic. Can we use let-else instead: https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html? Though this doesn't actually fix the panic issue.
• Unification of collection and type is never tested. Do we even need to be able to recognize this union? Maybe we do, but if we don't this is just unnecessary logic.