Effects: add DSL for declaration of contracts

- Introduce DSL for declaration of contracts. Functions and classes in
this DSL do not bear any computational semantics: in fact, they all do
not exist on runtime. Whole work of extracting semantics from such calls
is done by special parts of compiler

- To make distinguishing those declarations more robust and
convenient, introduce internal annotation @ContractsDSL

- Turn off InlineChecker inside contracts DSL. We do this, because some
functions from DSL should take any possible lambda, so we can't write
any type besides 'Function<R>'. However, InlineChecker will complain if
we will pass inlined lambda in such function -- though, this is false
positive because we know that functions from contracts DSL will never be
executed

- Change testData on HierarchyTestWithLib, where new enum from
kotlin.internal changed expected output

==========
Effect System introduction: 7/18

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/InlineChecker.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.diagnostics.Errors.*
+import org.jetbrains.kotlin.contracts.parsing.isFromContractDsl
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
@@ -59,10 +60,15 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
 
     override fun check(resolvedCall: ResolvedCall<*>, reportOn: PsiElement, context: CallCheckerContext) {
         val expression = resolvedCall.call.calleeExpression ?: return
+
         supportDefaultValueInline = context.languageVersionSettings.supportsFeature(LanguageFeature.InlineDefaultFunctionalParameters)
 
         //checking that only invoke or inlinable extension called on function parameter
         val targetDescriptor = resolvedCall.resultingDescriptor
+
+        // Omit inline checks for 'contract'-call because those calls will never be executed, so inline checking is pointless
+        if (targetDescriptor.isFromContractDsl()) return
+
         checkCallWithReceiver(context, targetDescriptor, resolvedCall.dispatchReceiver, expression)
         checkCallWithReceiver(context, targetDescriptor, resolvedCall.extensionReceiver, expression)
 

idea/testData/hierarchy/withLib/enum/Enum_verification.xml

@@ -9,9 +9,11 @@
     <node text="PrintMode in JTable (javax.swing)"/>
     <node text="ElementType (java.lang.annotation)"/>
     <node text="State in Thread (java.lang)"/>
-    <node text="RetentionPolicy (java.lang.annotation)"/>
     <node text="Type in Window (java.awt)"/>
-    <node text="Kind in KParameter (kotlin.reflect)"/>
+    <node text="RetentionPolicy (java.lang.annotation)"/>
+    <node text="InvocationKind (kotlin.internal.contracts)"/>
+    <node text="One ()"/>
+    <node text="G ()"/>
     <node text="FileWalkDirection (kotlin.io)"/>
     <node text="OnErrorAction (kotlin.io)"/>
     <node text="RegexOption (kotlin.text)"/>
@@ -22,9 +24,8 @@
     <node text="AnnotationTarget (kotlin.annotation)"/>
     <node text="AnnotationRetention (kotlin.annotation)"/>
     <node text="State (kotlin.collections)"/>
-    <node text="DeprecationLevel (kotlin)"/>
     <node text="LazyThreadSafetyMode (kotlin)"/>
-    <node text="One ()"/>
+    <node text="DeprecationLevel (kotlin)"/>
-    <node text="G ()"/>
+    <node text="Kind in KParameter (kotlin.reflect)"/>
   </node>
 </node>

libraries/stdlib/src/kotlin/internal/Annotations.kt

@@ -102,3 +102,9 @@ internal enum class RequireKotlinVersionKind {
     COMPILER_VERSION,
     API_VERSION,
 }
+
+/**
+ * Specifies that this declaration is a part of special DSL, used for constructing function's contract.
+ */
+@Retention(AnnotationRetention.BINARY)
+internal annotation class ContractsDsl

libraries/stdlib/src/kotlin/internal/contracts/ContractBuilder.kt

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlin.internal.contracts
+
+import kotlin.internal.ContractsDsl
+import kotlin.internal.InlineOnly
+
+@ContractsDsl
+internal interface ContractBuilder {
+    @ContractsDsl fun returns(): Returns
+    @ContractsDsl fun returns(value: Any?): Returns
+    @ContractsDsl fun returnsNotNull(): ReturnsNotNull
+    @ContractsDsl fun <R> callsInPlace(lambda: Function<R>, kind: InvocationKind = InvocationKind.UNKNOWN): CallsInPlace
+}
+
+@ContractsDsl
+internal enum class InvocationKind {
+    @ContractsDsl AT_MOST_ONCE,
+    @ContractsDsl AT_LEAST_ONCE,
+    @ContractsDsl EXACTLY_ONCE,
+    @ContractsDsl UNKNOWN
+}
+
+@ContractsDsl
+@InlineOnly
+internal inline fun contract(builder: ContractBuilder.() -> Unit) { }

libraries/stdlib/src/kotlin/internal/contracts/Effect.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlin.internal.contracts
+
+import kotlin.internal.ContractsDsl
+
+@ContractsDsl
+internal interface Effect
+
+@ContractsDsl
+internal interface ConditionalEffect : Effect
+
+@ContractsDsl
+internal interface SimpleEffect {
+    @ContractsDsl
+    infix fun implies(booleanExpression: Boolean): ConditionalEffect
+}
+
+
+@ContractsDsl
+internal interface Returns : SimpleEffect
+
+@ContractsDsl
+internal interface ReturnsNotNull : SimpleEffect
+
+@ContractsDsl
+internal interface CallsInPlace : SimpleEffect