fix generic type that has more than 2 params with only one constraint type

[sdghchj]

Describe the PR
fix generic type that has more than 2 params with only one constraint type.
Before, we have only onsidered generic type format like [x any, y any], but missed [x,y any].

Relation issue
#1490

[codecov]

Codecov Report

Patch coverage: 92.30% and project coverage change: +0.03 🎉

Comparison is base (aa3e8d5) 85.14% compared to head (5ea11a0) 85.18%.

❗ Current head 5ea11a0 differs from pull request most recent head 2317cc4. Consider uploading reports for the commit 2317cc4 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1506      +/-   ##
==========================================
+ Coverage   85.14%   85.18%   +0.03%     
==========================================
  Files          19       19              
  Lines        3616     3637      +21     
==========================================
+ Hits         3079     3098      +19     
- Misses        459      460       +1     
- Partials       78       79       +1     

Impacted Files	Coverage Δ
gen/gen.go	93.51% <ø> (ø)
field_parser.go	96.90% <33.33%> (-0.55%)	⬇️
generics.go	100.00% <100.00%> (ø)
operation.go	96.11% <100.00%> (+0.01%)	⬆️
parser.go	94.50% <100.00%> (+0.05%)	⬆️

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[ubogdan]

Could you add some unit tests to cover this change?

[sdghchj]

@ubogdan added

[ubogdan]

@sdghchj let's get this merged and release a new version.