Introduce 'mayHaveContract'-flag in stubs

This is needed for further commit, which supports contracts-based
smartcasts in partial body resolve mode.

NB: Stubs can be built from 3 sources:
- source code (contract presence can be checked by PSI)
- binary data (contract presence can be checked by Kotlin Metadata)
- decompiled sources

The last case is a bit of a headache, because usually bodies are omitted
in decompiled sources. To workaround it, we have to inject stubbed
contract-call in the body.

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt

@@ -20,6 +20,7 @@ import com.intellij.openapi.diagnostic.Logger
 import com.intellij.openapi.vfs.VirtualFile
 import org.jetbrains.kotlin.builtins.DefaultBuiltIns
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.contracts.ContractDeserializerImpl
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.descriptors.NotFoundClasses
 import org.jetbrains.kotlin.idea.caches.IDEKotlinBinaryClassCache
@@ -63,11 +64,16 @@ class DeserializerForClassfileDecompiler(
         val annotationAndConstantLoader =
                 BinaryClassAnnotationAndConstantLoaderImpl(moduleDescriptor, notFoundClasses, storageManager, classFinder)
 
+        val configuration = object : DeserializationConfiguration {
+            override val readDeserializedContracts: Boolean
+                get() = true
+        }
+
         deserializationComponents = DeserializationComponents(
-                storageManager, moduleDescriptor, DeserializationConfiguration.Default, classDataFinder, annotationAndConstantLoader,
+                storageManager, moduleDescriptor, configuration, classDataFinder, annotationAndConstantLoader,
                 packageFragmentProvider, ResolveEverythingToKotlinAnyLocalClassifierResolver(builtIns), LoggingErrorReporter(LOG),
                 LookupTracker.DO_NOTHING, JavaFlexibleTypeDeserializer, emptyList(), notFoundClasses,
-                ContractDeserializer.DEFAULT,
+                ContractDeserializerImpl(configuration),
                 extensionRegistryLite = JvmProtoBufUtil.EXTENSION_REGISTRY
         )
     }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/stubBuilder/CallableClsStubBuilder.kt

@@ -180,7 +180,8 @@ private class FunctionClsStubBuilder(
                 isExtension = functionProto.hasReceiver(),
                 hasBlockBody = true,
                 hasBody = Flags.MODALITY.get(functionProto.flags) != Modality.ABSTRACT,
-                hasTypeParameterListBeforeFunctionName = functionProto.typeParameterList.isNotEmpty()
+                hasTypeParameterListBeforeFunctionName = functionProto.typeParameterList.isNotEmpty(),
+                hasContract = functionProto.hasContract()
         )
     }
 }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/textBuilder/buildDecompiledText.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.idea.decompiler.textBuilder
 
 import com.intellij.openapi.util.TextRange
+import org.jetbrains.kotlin.contracts.description.ContractProviderKey
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.decompiler.navigation.ByDescriptorIndexer
 import org.jetbrains.kotlin.name.FqName
@@ -31,6 +32,7 @@ import org.jetbrains.kotlin.types.isFlexible
 private val DECOMPILED_CODE_COMMENT = "/* compiled code */"
 private val DECOMPILED_COMMENT_FOR_PARAMETER = "/* = compiled code */"
 private val FLEXIBLE_TYPE_COMMENT = "/* platform type */"
+private val DECOMPILED_CONTRACT_STUB = "contract { /* compiled contract */ }"
 
 fun DescriptorRendererOptions.defaultDecompilerRendererOptions() {
     withDefinedIn = false
@@ -89,7 +91,13 @@ fun buildDecompiledText(
         if (descriptor is FunctionDescriptor || descriptor is PropertyDescriptor) {
             if ((descriptor as MemberDescriptor).modality != Modality.ABSTRACT) {
                 if (descriptor is FunctionDescriptor) {
-                    builder.append(" { ").append(DECOMPILED_CODE_COMMENT).append(" }")
+                    with(builder) {
+                        append(" { ")
+                        if (descriptor.getUserData(ContractProviderKey)?.getContractDescription() != null) {
+                            append(DECOMPILED_CONTRACT_STUB).append("; ")
+                        }
+                        append(DECOMPILED_CODE_COMMENT).append(" }")
+                    }
                 }
                 else {
                     // descriptor instanceof PropertyDescriptor

idea/idea-analysis/src/org/jetbrains/kotlin/idea/stubindex/IdeStubIndexService.java

@@ -156,6 +156,10 @@ public class IdeStubIndexService extends StubIndexService {
             if (TypeIndexUtilKt.isProbablyNothing(stub.getPsi().getTypeReference())) {
                 sink.occurrence(KotlinProbablyNothingFunctionShortNameIndex.getInstance().getKey(), name);
             }
+
+            if (stub.mayHaveContract()) {
+                sink.occurrence(KotlinProbablyContractedFunctionShortNameIndex.getInstance().getKey(), name);
+            }
         }
 
         if (stub.isTopLevel()) {