Fix type stability of fill_similar

[MilesCranmer]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 5848900390

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 91.07%

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Totals
Change from base Build 5844012518:	0.02%
Covered Lines:	1081
Relevant Lines:	1187

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💛 - Coveralls

[github-actions]

Benchmark Results

	master	118bcbf...	t[master]/t[118bcbf...]
eval/ComplexF32/evaluation	14.8 ± 0.89 ms	14.5 ± 0.93 ms	1.02
eval/ComplexF64/evaluation	17.5 ± 1.2 ms	17.5 ± 1.2 ms	0.999
eval/Float32/derivative	21.3 ± 3.2 ms	20.7 ± 3.7 ms	1.03
eval/Float32/derivative_turbo	24.9 ± 3.4 ms	24.9 ± 3.7 ms	0.997
eval/Float32/evaluation	4.27 ± 0.33 ms	4.14 ± 0.31 ms	1.03
eval/Float32/evaluation_turbo	1.47 ± 0.068 ms	1.42 ± 0.073 ms	1.03
eval/Float64/derivative	28.3 ± 0.93 ms	29.3 ± 0.93 ms	0.968
eval/Float64/derivative_turbo	0.0336 ± 0.0013 s	0.0349 ± 0.0013 s	0.963
eval/Float64/evaluation	4.28 ± 0.34 ms	4.3 ± 0.32 ms	0.995
eval/Float64/evaluation_turbo	2.01 ± 0.087 ms	1.97 ± 0.11 ms	1.02
time_to_load	1.16 ± 0.077 s	1.13 ± 0.0075 s	1.02
utils/combine_operators	0.0726 ± 0.0043 ms	0.0706 ± 0.0039 ms	1.03
utils/convert/break_sharing	0.0516 ± 0.0016 ms	0.0525 ± 0.0022 ms	0.983
utils/convert/preserve_sharing	0.278 ± 0.0049 ms	0.278 ± 0.0043 ms	1
utils/copy/break_sharing	0.0532 ± 0.0019 ms	0.0544 ± 0.0031 ms	0.978
utils/copy/preserve_sharing	0.276 ± 0.0047 ms	0.277 ± 0.005 ms	0.995
utils/count_constants	29.4 ± 0.7 μs	29.5 ± 0.7 μs	0.997
utils/count_depth	0.0333 ± 0.0008 ms	0.0318 ± 0.0008 ms	1.05
utils/count_nodes	29.1 ± 0.7 μs	29 ± 0.7 μs	1
utils/get_set_constants!	0.119 ± 0.0019 ms	0.116 ± 0.0019 ms	1.02
utils/has_constants	10.8 ± 0.72 μs	10.9 ± 0.77 μs	0.989
utils/has_operators	3.01 ± 0.067 μs	3.03 ± 0.078 μs	0.993
utils/index_constants	0.0938 ± 0.0041 ms	0.0935 ± 0.0042 ms	1
utils/is_constant	11.7 ± 0.72 μs	11.1 ± 0.68 μs	1.05
utils/simplify_tree	0.214 ± 0.02 ms	0.216 ± 0.022 ms	0.992
utils/string_tree	0.392 ± 0.0087 ms	0.397 ± 0.018 ms	0.988

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.
Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).