Handle exceptions

[JSAbrahams]

Relevant issues

• Do not merge before #380
• Resolves #374
• Created #383
• Created #385
• Created #386

  Summary

Fix handle:

• Checks that handle arms cover all exceptions.
• Also allow that (only) parents are covered of exceptions.
• Current logic allows handle cover more exceptions than may be raised.

Added Tests

Happy

• Handle
• Handle cover only parent of exception
• Exception in function no covered but in function signature

Sad

• Using undefined variable in match arm body
• Exception in function not covered

[codecov[bot]]

Codecov Report

Merging #382 (10916c4) into develop (a9aed8a) will increase coverage by 0.01%. The diff coverage is 82.82%.

@@             Coverage Diff             @@
##           develop     #382      +/-   ##
===========================================
+ Coverage    87.05%   87.06%   +0.01%     
===========================================
  Files          109      109              
  Lines        12014    12008       -6     
===========================================
- Hits         10459    10455       -4     
+ Misses        1555     1553       -2     

Impacted Files	Coverage Δ
src/check/constrain/generate/resources.rs	94.73% <ø> (+18.37%)	:arrow_up:
src/check/constrain/unify/link.rs	90.62% <ø> (-0.29%)	:arrow_down:
src/check/constrain/unify/ty.rs	71.28% <ø> (+1.12%)	:arrow_up:
src/generate/convert/mod.rs	93.82% <45.45%> (-0.08%)	:arrow_down:
src/check/constrain/generate/statement.rs	82.22% <81.48%> (-1.12%)	:arrow_down:
src/check/constrain/generate/definition.rs	90.74% <87.50%> (-1.09%)	:arrow_down:
src/check/constrain/generate/control_flow.rs	91.50% <88.57%> (-1.90%)	:arrow_down:
src/check/constrain/constraint/expected.rs	86.91% <100.00%> (+0.42%)	:arrow_up:
src/check/constrain/generate/call.rs	88.34% <100.00%> (-0.36%)	:arrow_down:
src/check/constrain/generate/env.rs	93.00% <100.00%> (-0.21%)	:arrow_down:
... and 10 more

[JSAbrahams]

Should test that error raised when exception is not handled. Also happy test for where it is not handled locally in a function, but the function signature does specify the exception.