Add compatibility warning for suspend conversions

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/suspendConversionUtils.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.resolve.calls.components
 import org.jetbrains.kotlin.builtins.*
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.ParameterDescriptor
+import org.jetbrains.kotlin.resolve.calls.inference.model.LowerPriorityToPreserveCompatibility
 import org.jetbrains.kotlin.resolve.calls.model.*
 import org.jetbrains.kotlin.types.UnwrappedType
 
@@ -53,6 +54,8 @@ object SuspendTypeConversions : ParameterTypeConversion {
 
         candidate.resolvedCall.registerArgumentWithSuspendConversion(argument, nonSuspendParameterType)
 
+        candidate.addDiagnostic(LowerPriorityToPreserveCompatibility)
+
         return nonSuspendParameterType
     }
 }