fix(gen): re-use parameter type

[tdakkota]

Fixes #1177.

[codecov]

Codecov Report

Attention: Patch coverage is 69.76744% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 73.85%. Comparing base (dfdcdd7) to head (81d99fa).
Report is 1 commits behind head on main.

Files	Patch %	Lines
gen/gen_parameters.go	65.00%	4 Missing and 3 partials ⚠️
gen/tstorage.go	73.33%	2 Missing and 2 partials ⚠️
gen/genctx.go	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1197      +/-   ##
==========================================
- Coverage   73.87%   73.85%   -0.02%     
==========================================
  Files         189      189              
  Lines       12772    12807      +35     
==========================================
+ Hits         9435     9459      +24     
- Misses       2796     2802       +6     
- Partials      541      546       +5     

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