Parse expressions without interpolation

[MilesCranmer]

I think this fixes custom operators in MilesCranmer/SymbolicRegression.jl#469

cc @gm89uk

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	e79b95c...	master / e79b95c...
eval/ComplexF32/evaluation	7.23 ± 0.55 ms	7.25 ± 0.55 ms	0.997 ± 0.11
eval/ComplexF64/evaluation	10.8 ± 0.98 ms	10.8 ± 0.92 ms	1 ± 0.12
eval/Float32/derivative	11.8 ± 0.59 ms	11.8 ± 0.56 ms	1.01 ± 0.07
eval/Float32/derivative_turbo	11.8 ± 0.67 ms	11.8 ± 0.6 ms	1 ± 0.077
eval/Float32/evaluation	2.92 ± 0.29 ms	2.76 ± 0.29 ms	1.06 ± 0.15
eval/Float32/evaluation_bumper	0.582 ± 0.018 ms	0.579 ± 0.015 ms	1.01 ± 0.04
eval/Float32/evaluation_turbo	0.535 ± 0.03 ms	0.528 ± 0.03 ms	1.01 ± 0.082
eval/Float32/evaluation_turbo_bumper	0.581 ± 0.017 ms	0.578 ± 0.016 ms	1.01 ± 0.041
eval/Float64/derivative	14.7 ± 1 ms	14.7 ± 0.95 ms	0.999 ± 0.095
eval/Float64/derivative_turbo	14.7 ± 0.89 ms	14.8 ± 1.1 ms	0.995 ± 0.096
eval/Float64/evaluation	3.15 ± 0.33 ms	3.14 ± 0.33 ms	1 ± 0.15
eval/Float64/evaluation_bumper	1.21 ± 0.045 ms	1.19 ± 0.044 ms	1.01 ± 0.053
eval/Float64/evaluation_turbo	1.01 ± 0.063 ms	1.01 ± 0.067 ms	1 ± 0.091
eval/Float64/evaluation_turbo_bumper	1.21 ± 0.045 ms	1.19 ± 0.042 ms	1.01 ± 0.052
utils/combine_operators/break_sharing	0.0419 ± 0.0024 ms	0.0419 ± 0.0021 ms	1 ± 0.077
utils/convert/break_sharing	29.7 ± 4.4 μs	29.8 ± 4 μs	0.997 ± 0.2
utils/convert/preserve_sharing	0.101 ± 0.0069 ms	0.103 ± 0.0082 ms	0.982 ± 0.1
utils/copy/break_sharing	29.6 ± 4.3 μs	29.5 ± 4.1 μs	1 ± 0.2
utils/copy/preserve_sharing	0.102 ± 0.0073 ms	0.104 ± 0.0083 ms	0.984 ± 0.11
utils/count_constant_nodes/break_sharing	13.1 ± 1.5 μs	13.7 ± 1.5 μs	0.955 ± 0.15
utils/count_constant_nodes/preserve_sharing	0.086 ± 0.0053 ms	0.0874 ± 0.0063 ms	0.984 ± 0.094
utils/count_depth/break_sharing	14.3 ± 1.7 μs	14.3 ± 1.9 μs	1 ± 0.18
utils/count_nodes/break_sharing	12.2 ± 1.5 μs	12.8 ± 1.4 μs	0.959 ± 0.16
utils/count_nodes/preserve_sharing	0.0868 ± 0.0053 ms	0.088 ± 0.0061 ms	0.987 ± 0.091
utils/get_set_constants!/break_sharing	0.0341 ± 0.003 ms	0.034 ± 0.0029 ms	1 ± 0.12
utils/get_set_constants!/preserve_sharing	0.18 ± 0.0093 ms	0.182 ± 0.01 ms	0.991 ± 0.076
utils/get_set_constants_parametric	0.0506 ± 0.0066 ms	0.0514 ± 0.0062 ms	0.985 ± 0.18
utils/has_constants/break_sharing	7.64 ± 1.1 μs	7.73 ± 0.95 μs	0.99 ± 0.19
utils/has_operators/break_sharing	2.58 ± 0.17 μs	2.52 ± 0.19 μs	1.02 ± 0.1
utils/hash/break_sharing	24 ± 2.4 μs	24.4 ± 2.4 μs	0.983 ± 0.14
utils/hash/preserve_sharing	0.101 ± 0.0064 ms	0.1 ± 0.0057 ms	1.01 ± 0.086
utils/index_constant_nodes/break_sharing	30.4 ± 3.1 μs	30.2 ± 3 μs	1.01 ± 0.14
utils/index_constant_nodes/preserve_sharing	0.103 ± 0.006 ms	0.104 ± 0.0073 ms	0.994 ± 0.091
utils/is_constant/break_sharing	8.28 ± 1 μs	8.41 ± 1.1 μs	0.984 ± 0.18
utils/simplify_tree/break_sharing	26.5 ± 2.8 μs	26.8 ± 2.7 μs	0.99 ± 0.14
utils/simplify_tree/preserve_sharing	0.109 ± 0.0061 ms	0.109 ± 0.0064 ms	0.992 ± 0.081
utils/string_tree/break_sharing	0.477 ± 0.024 ms	0.48 ± 0.022 ms	0.994 ± 0.067
utils/string_tree/preserve_sharing	0.571 ± 0.022 ms	0.57 ± 0.022 ms	1 ± 0.055
time_to_load	0.23 ± 0.0014 s	0.233 ± 0.00064 s	0.986 ± 0.0066

Memory benchmarks

	master	e79b95c...	master / e79b95c...
eval/ComplexF32/evaluation	0.972 k allocs: 2.49 MB	0.978 k allocs: 2.5 MB	0.994
eval/ComplexF64/evaluation	0.999 k allocs: 5.09 MB	0.999 k allocs: 5.09 MB	1
eval/Float32/derivative	4.64 k allocs: 17.5 MB	4.7 k allocs: 17.7 MB	0.987
eval/Float32/derivative_turbo	4.64 k allocs: 17.5 MB	4.69 k allocs: 17.7 MB	0.99
eval/Float32/evaluation	0.996 k allocs: 1.3 MB	0.984 k allocs: 1.28 MB	1.01
eval/Float32/evaluation_bumper	0.303 k allocs: 0.393 MB	0.303 k allocs: 0.393 MB	1
eval/Float32/evaluation_turbo	0.966 k allocs: 1.26 MB	0.963 k allocs: 1.25 MB	1
eval/Float32/evaluation_turbo_bumper	0.303 k allocs: 0.393 MB	0.303 k allocs: 0.393 MB	1
eval/Float64/derivative	4.79 k allocs: 0.035 GB	4.82 k allocs: 0.0353 GB	0.994
eval/Float64/derivative_turbo	4.83 k allocs: 0.0353 GB	4.78 k allocs: 0.035 GB	1.01
eval/Float64/evaluation	0.996 k allocs: 2.55 MB	0.975 k allocs: 2.5 MB	1.02
eval/Float64/evaluation_bumper	0.303 k allocs: 0.771 MB	0.303 k allocs: 0.771 MB	1
eval/Float64/evaluation_turbo	0.978 k allocs: 2.5 MB	0.99 k allocs: 2.53 MB	0.988
eval/Float64/evaluation_turbo_bumper	0.303 k allocs: 0.771 MB	0.303 k allocs: 0.771 MB	1
utils/combine_operators/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/convert/break_sharing	2 k allocs: 0.123 MB	2 k allocs: 0.123 MB	1
utils/convert/preserve_sharing	2.4 k allocs: 0.192 MB	2.4 k allocs: 0.192 MB	1
utils/copy/break_sharing	2 k allocs: 0.123 MB	2 k allocs: 0.123 MB	1
utils/copy/preserve_sharing	2.4 k allocs: 0.192 MB	2.4 k allocs: 0.192 MB	1
utils/count_constant_nodes/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_constant_nodes/preserve_sharing	0.404 k allocs: 0.0696 MB	0.404 k allocs: 0.0696 MB	1
utils/count_depth/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_nodes/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_nodes/preserve_sharing	0.404 k allocs: 0.0696 MB	0.404 k allocs: 0.0696 MB	1
utils/get_set_constants!/break_sharing	0.898 k allocs: 25.2 kB	0.898 k allocs: 25.2 kB	1
utils/get_set_constants!/preserve_sharing	1.7 k allocs: 0.138 MB	1.7 k allocs: 0.138 MB	1
utils/get_set_constants_parametric	1.42 k allocs: 0.0663 MB	1.42 k allocs: 0.0663 MB	1
utils/has_constants/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/has_operators/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/hash/break_sharing	0.104 k allocs: 2.52 kB	0.104 k allocs: 2.52 kB	1
utils/hash/preserve_sharing	0.504 k allocs: 0.0711 MB	0.504 k allocs: 0.0711 MB	1
utils/index_constant_nodes/break_sharing	2.1 k allocs: 0.094 MB	2.1 k allocs: 0.094 MB	1
utils/index_constant_nodes/preserve_sharing	2.5 k allocs: 0.163 MB	2.5 k allocs: 0.163 MB	1
utils/is_constant/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/simplify_tree/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/simplify_tree/preserve_sharing	0.404 k allocs: 0.0696 MB	0.404 k allocs: 0.0696 MB	1
utils/string_tree/break_sharing	11.8 k allocs: 1.04 MB	11.8 k allocs: 1.04 MB	1
utils/string_tree/preserve_sharing	12.2 k allocs: 1.11 MB	12.2 k allocs: 1.11 MB	1
time_to_load	0.159 k allocs: 11.2 kB	0.159 k allocs: 11.2 kB	1