Add converter torch aten::histc

[xadupre]

Fixes #2794.

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.50%. Comparing base (5ae26d9) to head (86dd6e0).
⚠️ Report is 6 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
onnxscript/function_libs/torch_lib/ops/core.py	90.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2796      +/-   ##
==========================================
- Coverage   70.51%   70.50%   -0.01%     
==========================================
  Files         228      228              
  Lines       27214    27114     -100     
  Branches     2737     2726      -11     
==========================================
- Hits        19189    19116      -73     
+ Misses       7090     7065      -25     
+ Partials      935      933       -2     

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[xadupre]

The rounding for float16 is puzzling.

[titaiwangms]

Looks like it's not ready yet?

[Copilot]

Pull request overview

Adds an ONNXScript converter for aten::histc to unblock export of models that use torch.histc (Fixes #2794), and wires it into the torch-lib op test matrix with new e2e coverage.

Changes:

• Implement aten::histc converter in onnxscript/function_libs/torch_lib/ops/core.py.
• Register histc in the torch-lib op test data with targeted skips.
• Add e2e export + reference-check tests for torch.histc (float; float16 currently skipped due to upstream issue).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
tests/function_libs/torch_lib/ops_test_data.py	Adds histc to the op list with skips for min==max and float16.
tests/function_libs/torch_lib/e2e_ops_tests.py	Adds e2e tests for exporting and numerically validating torch.histc.
onnxscript/function_libs/torch_lib/ops/core.py	Introduces a trace-only ONNX lowering for aten::histc.