I enabled code contract checking in roslyn\Src\Compilers\Core\Portable\CodeAnalysis and I get:
C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\CodeAnalysis.csproj(667,3): warning MSB4011: "C:\
Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\Common.CodeContracts.props" cannot be imported again.
It was already imported at "C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\CodeAnalysis.csproj (66
6,3)". This is most likely a build authoring error. This subsequent import will be ignored.
I enabled code contract checking in roslyn\Src\Compilers\Core\Portable\CodeAnalysis and I get:
C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\CodeAnalysis.csproj(667,3): warning MSB4011: "C:\ Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\Common.CodeContracts.props" cannot be imported again. It was already imported at "C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Portable\CodeAnalysis.csproj (66 6,3)". This is most likely a build authoring error. This subsequent import will be ignored.
"C:\Users\carr27\Documents\GitHub\roslyn\src\RoslynLight.sln" (default target) (1) -> "C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\CodeAnalysisTest\CodeAnalysisTest.csproj" (default target) (2) -> "C:\Users\carr27\Documents\GitHub\roslyn\src\Test\Utilities\TestUtilities.csproj" (default target) (4) -> "C:\Users\carr27\Documents\GitHub\roslyn\src\Compilers\Core\Desktop\CodeAnalysis.Desktop.csproj" (default target) (5) -