Dictionary exposes internal type comparer

[MarcoRossignoli]

Fixes https://github.com/dotnet/corefx/issues/26033

This is my first pull on this repo(maybe i'm in the wrong place). I don't know if there is a "guide" to do "cross repo" test for core*.
If i want to add a test on corefx with this "merge", do i have to wait and clean/rebuild?

cc: @jkotas

[danmoseley]

@maryamariyan could you please guide @MarcoRossignoli through writing a matching CoreFX test, and help him verify it against his private CoreCLR change? Since you have been doing this recnetly.

[maryamariyan]

@danmosemsft sure.

@MarcoRossignoli here's what you need to do:

• Build coreclr locally in release mode. You can skip tests to complete the build faster.

C:\git\coreclr> git clean -fdx 
C:\git\coreclr> build -release -skiptests 

• Follow instructions to run corefx tests using local coreclr bits here

C:\git\corefx> git clean -fdx
C:\git\corefx> build.cmd -release -- /p:CoreCLROverridePath=C:\git\coreclr\bin\Product\Windows_NT.x64.Release\
C:\git\corefx> msbuild src\System.Collections\tests\ /t:rebuildandtest /p:ConfigurationGroup:release

[MarcoRossignoli]

@dotnet-bot test Tizen armel Cross Checked Innerloop Build and Test please

[stephentoub]

Shouldn't this be EqualityComparer<TKey> rather than EqualityComparer<string>? Maybe we're just not testing this code path?

[stephentoub]

Ah, I see why it works ok... TKey must be a string for _comparer to get set to NonRandomizedStringEqualityComparer.

[MarcoRossignoli]

actually compile also with TKey because the constraints are respected and for now we've only optimization with string TKey, i think with EqualityComparer of string the intentions are more clear. Do you agree?

[jkotas]

Thanks!