Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

mcs/class/referencesource/mscorlib/system/diagnostics/contracts/contracts.cs

@@ -28,7 +28,9 @@
 #elif BARTOK_RUNTIME
 
 #else // CLR
+#if !MONO
 #define FEATURE_UNTRUSTED_CALLERS
+#endif
 #define FEATURE_RELIABILITY_CONTRACTS
 #define FEATURE_SERIALIZATION
 #endif

mcs/class/referencesource/mscorlib/system/diagnostics/contracts/contractsbcl.cs

@@ -38,8 +38,10 @@ using System.Runtime.ConstrainedExecution;
 #endif
 #if FEATURE_UNTRUSTED_CALLERS
 using System.Security;
+#if !MONO
 using System.Security.Permissions;
 #endif
+#endif
 
 namespace System.Diagnostics.Contracts {
 
@@ -57,8 +59,10 @@ namespace System.Diagnostics.Contracts {
         [SecuritySafeCritical]
         static partial void AssertMustUseRewriter(ContractFailureKind kind, String contractKind)
         {
+#if !NETCORE
             if (_assertingMustUseRewriter)
                 System.Diagnostics.Assert.Fail("Asserting that we must use the rewriter went reentrant.", "Didn't rewrite this mscorlib?");
+#endif
             _assertingMustUseRewriter = true;
 
             // For better diagnostics, report which assembly is at fault.  Walk up stack and