Add better errors for `rand`

[coveralls]

Pull Request Test Coverage Report for Build 7337122251

Warning: This coverage report may be inaccurate.

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• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 94.279%

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Totals
Change from base Build 7336986649:	0.03%
Covered Lines:	1269
Relevant Lines:	1346

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💛 - Coveralls

[github-actions[bot]]

Benchmark Results

	master	97441d71bb179d...	t[master]/t[97441d71bb179d...]
eval/ComplexF32/evaluation	7.36 ± 0.44 ms	7.41 ± 0.43 ms	0.993
eval/ComplexF64/evaluation	9.65 ± 0.67 ms	9.7 ± 0.69 ms	0.995
eval/Float32/derivative	11.5 ± 2 ms	11.4 ± 2.2 ms	1.01
eval/Float32/derivative_turbo	12.3 ± 2.1 ms	12.4 ± 2 ms	0.991
eval/Float32/evaluation	2.71 ± 0.23 ms	2.72 ± 0.23 ms	0.997
eval/Float32/evaluation_turbo	0.634 ± 0.037 ms	0.673 ± 0.031 ms	0.941
eval/Float64/derivative	15.2 ± 1.5 ms	15.4 ± 0.7 ms	0.99
eval/Float64/derivative_turbo	15 ± 0.95 ms	15.8 ± 0.71 ms	0.955
eval/Float64/evaluation	2.86 ± 0.25 ms	2.88 ± 0.25 ms	0.992
eval/Float64/evaluation_turbo	1.18 ± 0.084 ms	1.17 ± 0.065 ms	1
utils/combine_operators/break_sharing	0.0396 ± 0.0022 ms	0.0398 ± 0.0025 ms	0.994
utils/convert/break_sharing	28.5 ± 0.68 μs	28.4 ± 0.61 μs	1
utils/convert/preserve_sharing	0.131 ± 0.0048 ms	0.131 ± 0.0033 ms	1
utils/copy/break_sharing	29 ± 0.7 μs	30.3 ± 1.6 μs	0.958
utils/copy/preserve_sharing	0.132 ± 0.004 ms	0.13 ± 0.004 ms	1.01
utils/count_constants/break_sharing	11.4 ± 0.2 μs	11.4 ± 0.22 μs	0.995
utils/count_constants/preserve_sharing	0.113 ± 0.0031 ms	0.114 ± 0.0028 ms	0.999
utils/count_depth/break_sharing	17.3 ± 0.4 μs	17.9 ± 0.44 μs	0.969
utils/count_nodes/break_sharing	10.2 ± 0.16 μs	10.2 ± 0.17 μs	0.998
utils/count_nodes/preserve_sharing	0.116 ± 0.0027 ms	0.116 ± 0.0029 ms	1
utils/get_set_constants!/break_sharing	0.0529 ± 0.00085 ms	0.0529 ± 0.00085 ms	1
utils/get_set_constants!/preserve_sharing	0.326 ± 0.0074 ms	0.331 ± 0.0078 ms	0.983
utils/has_constants/break_sharing	4.32 ± 0.22 μs	4.34 ± 0.22 μs	0.997
utils/has_operators/break_sharing	1.78 ± 0.02 μs	1.78 ± 0.021 μs	0.999
utils/hash/break_sharing	30.2 ± 0.49 μs	30.2 ± 0.55 μs	0.998
utils/hash/preserve_sharing	0.136 ± 0.0031 ms	0.135 ± 0.0029 ms	1.01
utils/index_constants/break_sharing	27.8 ± 0.76 μs	28.3 ± 0.78 μs	0.984
utils/index_constants/preserve_sharing	0.13 ± 0.0036 ms	0.132 ± 0.0031 ms	0.99
utils/is_constant/break_sharing	4.93 ± 0.22 μs	4.93 ± 0.23 μs	1
utils/simplify_tree/break_sharing	0.245 ± 0.02 ms	0.254 ± 0.021 ms	0.964
utils/simplify_tree/preserve_sharing	0.382 ± 0.022 ms	0.386 ± 0.023 ms	0.989
utils/string_tree/break_sharing	0.592 ± 0.02 ms	0.588 ± 0.02 ms	1.01
utils/string_tree/preserve_sharing	0.719 ± 0.026 ms	0.728 ± 0.025 ms	0.987
time_to_load	0.703 ± 0.014 s	0.739 ± 0.0085 s	0.952

[sweep-ai[bot]]

Apply Sweep Rules to your PR?

• [ ] Apply: All new business logic should have corresponding unit tests.
• [ ] Apply: Refactor large functions to be more modular.
• [ ] Apply: Add docstrings to all functions and file headers.