New Analyzer: Prevent behavioral change in built-in operators for IntPtr and UIntPtr

[buyaa-n]

Fixes dotnet/runtime#74022

With numeric IntPtr feature, System.IntPtr and System.UIntPtr gained some built-in operators (conversions, unary and binary). Those now might throw when overflowing within checked context or not throw in unchecked context compared to the previous "user-defined" operators , which is causing behavioral change in .NET 7.

This PR only includes the analyzer, fixer is not planned in 7.0 and also the preferred fix might be: IDE0049 should be updated to suggest converting IntPtr to nint and UIntPtr to nuint. So fixer need to be added after it added to IDE0049

Detect places where the behavioral changes would be happening and war, scenarios:

• For IntPtr
  • operator +(IntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • operator -(IntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • explicit operator IntPtr(long): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 32-bit contexts;
  • explicit operator void*(IntPtr): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • explicit operator IntPtr(void*): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • explicit operator int(IntPtr): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 64-bit contexts;
• For UIntPtr
  • operator +(UIntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • operator -(UIntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before;
  • explicit operator UIntPtr(ulong): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 32-bit contexts;
  • explicit operator uint(UIntPtr): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 64-bit contexts;

• These analyzer should be triggered only if the underlying runtime supports numeric IntPtr feature, i.e. check if System.Runtime.CompilerServices.RuntimeFeature.NumericIntPtr is available in corelib as

Suggested severity : "Warning"
Suggested category : "Reliability"

CC @jeffhandley @tannergooding @eerhardt

[codecov]

Codecov Report

Merging #6153 (305e134) into main (a26d1a2) will increase coverage by 0.00%.
The diff coverage is 97.08%.

Additional details and impacted files

@@            Coverage Diff            @@
##             main    #6153     +/-   ##
=========================================
  Coverage   96.03%   96.03%             
=========================================
  Files        1348     1354      +6     
  Lines      309832   311095   +1263     
  Branches     9967    10006     +39     
=========================================
+ Hits       297534   298775   +1241     
- Misses       9900     9910     +10     
- Partials     2398     2410     +12     

[jeffhandley]

I left a couple comments on the messages, but it looks good to me. We should wait for signoff from @tannergooding on the functional behavior though.

[buyaa-n]

After testing with runtime and a few other repos it showed that there is no many cases that the behavioral change is a real issue and needs wrapping with checked/unchecked, so we decided to degrade the severity level to info.

@jmarolf @mavasani @JoeRobich this the last analyzer we would like to merge in 7.0, I don't see any 7.0 branch created in the repo, is the main is the correct branch for .Net 7changes?

[buyaa-n]

Confirmed that the main is the correct branch, merging