Path to a friendlier language

[plajjan]

• [x] exceptions #1463
• [x] better error messages #1554 #1559
• [x] support testing #1524
• [x] #1426
• [x] #2050
• [x] #1458
• [ ] #2098
  • 4w
• [ ] #1693
  • 1w
• [ ] #1044
  • 4w
• [ ] #1502
  • 2w
• [ ] #1859
  • 1-2w
• [ ] #1906
  • 2w
• [ ] #1632
  • 4w
  • high likelihood of unknowns, but should be relatively easy to tackle / decide
  • lots of pill
• [ ] #850
  • high risk of unknowns
  • some design choices we need to agree on
  • can unions be freely inferred? can get very large unions - "anything OK" from type perspective which doesn't reflect developer intent
• [x] #1713
  • x
• [ ] #834
• [ ] #2099
• [ ] TBD!? remove variable shadowing
• [ ] TBD!? add module / method shadowing #1508