Make 'throws' non-optional in type structs

[codecov[bot]]

Codecov Report

Merging #723 (c5a8baf) into main (4d07abd) will increase coverage by 0.07%. The diff coverage is 93.86%.

@@            Coverage Diff             @@
##             main     #723      +/-   ##
==========================================
+ Coverage   85.13%   85.21%   +0.07%     
==========================================
  Files          62       62              
  Lines       12842    12882      +40     
==========================================
+ Hits        10933    10977      +44     
+ Misses       1909     1905       -4     

Files	Coverage Δ
crates/escalier_hm/src/context.rs	97.85% <100.00%> (-0.02%)	:arrow_down:
crates/escalier_hm/src/folder.rs	89.59% <100.00%> (ø)
crates/escalier_hm/src/util.rs	77.43% <100.00%> (+0.06%)	:arrow_up:
crates/escalier_hm/src/visitor.rs	56.58% <100.00%> (ø)
crates/escalier_interop/src/parse.rs	91.49% <100.00%> (+0.03%)	:arrow_up:
crates/escalier_hm/src/types.rs	87.86% <94.44%> (+0.22%)	:arrow_up:
crates/escalier_hm/src/unify.rs	85.83% <96.00%> (-0.08%)	:arrow_down:
crates/escalier_hm/src/infer.rs	94.89% <95.87%> (+0.07%)	:arrow_up:
crates/escalier_hm/src/infer_class.rs	80.31% <63.63%> (+0.41%)	:arrow_up: