Project-system: FastUpToDate fails if PreserveNewer file has same timestamp as source

[panopticoncentral]

1>FastUpToDate: Latest write timestamp on input is 8/25/2017 6:03:00 PM on 'D:\repos\roslyn\Binaries\Obj\CodeAnalysis\CodeAnalysis.csproj.nuget.g.props'. (CodeAnalysis)
1>FastUpToDate: Earliest write timestamp on output is 8/27/2017 4:11:15 AM on 'D:\repos\roslyn\Binaries\Obj\CodeAnalysis\Debug\Microsoft.CodeAnalysis.xml'. (CodeAnalysis)
1>FastUpToDate: Checking PreserveNewest file 'C:\Users\jcouv\.nuget\packages\microsoft.diasymreader.native\1.7.0-private-25604\runtimes\win\native\Microsoft.DiaSymReader.Native.amd64.dll': (CodeAnalysis)
1>FastUpToDate:     Write 8/5/2017 1:23:10 AM: 'C:\Users\jcouv\.nuget\packages\microsoft.diasymreader.native\1.7.0-private-25604\runtimes\win\native\Microsoft.DiaSymReader.Native.amd64.dll'. (CodeAnalysis)
1>FastUpToDate:     Output file write 8/5/2017 1:23:10 AM: 'D:\repos\roslyn\Binaries\Debug\Dlls\CodeAnalysis\Microsoft.DiaSymReader.Native.amd64.dll'. (CodeAnalysis)
1>FastUpToDate: Project is not up to date. (CodeAnalysis)
1>------ Build started: Project: CodeAnalysis, Configuration: Debug Any CPU ------
1>CodeAnalysis -> D:\repos\roslyn\Binaries\Debug\Dlls\CodeAnalysis\Microsoft.CodeAnalysis.dll

[jcouv]

Thanks Paul.
Is this bug specific to ref assemblies or would apply even when ref assemblies are turned off?

FYI @CyrusNajmabadi

[panopticoncentral]

Not specific to ref assemblies.

[davkean]

@panopticoncentral I've got a fix this - I'll take it.

[davkean]

This is fixed and will appear in the next public release of 15.4.

[gulbanana]

i just pressed F6 in 15.4 preview 3 and nothing happened. this is the most joy i have felt in almost two years

[davkean]

@gulbanana Not sure I follow - are saying that the solution didn't build? Or you are saying that the up-to-date check worked?

[gulbanana]

it worked perfectly 🥇

[davkean]

Awesome!