Fix allocation in DateTime.TryParse when it returns false

[stephentoub]

On some failure paths, it was boxing a char or an int that would have been used as part of creating an exception on a Parse path but that's ignored on a TryParse path. This avoids that boxing by storing those values into a dedicated int field on the DateTimeResult. While doing this, I also consolidated several other fields, such that this not only avoids the boxing, it also results in a net reduction of the size of DateTimeResult (it's passed around by ref, so this only slightly reduces a zeroing burden).

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Tests).Assembly).Run(args);

[HideColumns("Error", "StdDev", "Median", "RatioSD")]
[MemoryDiagnoser(false)]
public class Tests
{
    [Benchmark]
    [Arguments("hello")]
    public bool TryParse(string input) => DateTime.TryParse(input, out _);
}

Method	Toolchain	input	Mean	Ratio	Allocated	Alloc Ratio
TryParse	\main\corerun.exe	hello	39.22 ns	1.00	24 B	1.00
TryParse	\pr\corerun.exe	hello	34.98 ns	0.89	-	0.00

Fixes #90907

[ghost]

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Issue Details

---

On some failure paths, it was boxing a char or an int that would have been used as part of creating an exception on a Parse path but that's ignored on a TryParse path. This avoids that boxing by storing those values into a dedicated int field on the DateTimeResult. While doing this, I also consolidated several other fields, such that this not only avoids the boxing, it also results in a net reduction of the size of DateTimeResult (it's passed around by ref, so this only slightly reduces a zeroing burden).

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Tests).Assembly).Run(args);

[HideColumns("Error", "StdDev", "Median", "RatioSD")]
[MemoryDiagnoser(false)]
public class Tests
{
    [Benchmark]
    [Arguments("hello")]
    public bool TryParse(string input) => DateTime.TryParse(input, out _);
}

Method	Toolchain	input	Mean	Ratio	Allocated	Alloc Ratio
TryParse	\main\corerun.exe	hello	39.22 ns	1.00	24 B	1.00
TryParse	\pr\corerun.exe	hello	34.98 ns	0.89	-	0.00

Fixes #90907

Author:	stephentoub
Assignees:	-
Labels:	area-System.Globalization
Milestone:	-

[ShreyasJejurkar]

This is quite a good catch! 💯