Fix TryParseBigIntegerHexOrBinaryNumberStyle

[kzrnm]

Since the - operator has higher precedence than the ^ operator, leading ^ signBits - signBits is always equal to leading.

Related #95543

[ghost]

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Issue Details

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Since the - operator has higher precedence than the ^ operator, leading ^ signBits - signBits is always equal to leading.

Author:	kzrnm
Assignees:	-
Labels:	area-System.Numerics, community-contribution
Milestone:	-

[tannergooding]

Good catch. Is there an explicit test we can add to cover this?

[kzrnm]

I think the test for values whose absolute value is greater than 0x7FFFFFFF and less than 0x100000000 can cover this.
I added those tests to Hex/Bin.

cd src\libraries\System.Runtime.Numerics\tests

# Passed
dotnet build /t:Test /p:XUnitOptions="-class System.Numerics.Tests.parseTest" 

# Failed
git checkout main ../src/System/Number.BigInteger.cs
dotnet build /t:Test /p:XUnitOptions="-class System.Numerics.Tests.parseTest"  

[huoyaoyuan]

I'd like to add tests for non-edge cases that fall into this branch, both even and odd numbers.

Thank you again for discovering these! I'm really busy to complete things recently.