[FIR] Add contract renderer

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirContractDeserializer.kt

@@ -125,16 +125,20 @@ class FirContractDeserializer(private val c: FirDeserializationContext) {
 
         val valueParameterIndex = proto.valueParameterReference - 1
 
+        val name: String
         val typeRef = if (valueParameterIndex < 0) {
+            name = "this"
             ownerFunction.receiverTypeRef
         } else {
-            ownerFunction.valueParameters.getOrNull(valueParameterIndex)?.returnTypeRef
+            val parameter = ownerFunction.valueParameters.getOrNull(valueParameterIndex) ?: return null
+            name = parameter.name.asString()
+            parameter.returnTypeRef
         } ?: return null
 
         return if (!typeRef.isBoolean)
-            ConeValueParameterReference(valueParameterIndex)
+            ConeValueParameterReference(valueParameterIndex, name)
         else
-            ConeBooleanValueParameterReference(valueParameterIndex)
+            ConeBooleanValueParameterReference(valueParameterIndex, name)
     }
 
     private fun ProtoBuf.Effect.InvocationKind.toDescriptorInvocationKind(): InvocationKind? = when (this) {

compiler/fir/tree/src/org/jetbrains/kotlin/fir/contracts/description/ConeContractRenderer.kt

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.contracts.description
+
+import org.jetbrains.kotlin.contracts.description.expressions.*
+
+class ConeContractRenderer(private val builder: StringBuilder) : ConeContractDescriptionVisitor<Unit, Nothing?>() {
+    override fun visitConditionalEffectDeclaration(conditionalEffect: ConeConditionalEffectDeclaration, data: Nothing?) {
+        conditionalEffect.effect.accept(this, data)
+        builder.append(" -> ")
+        conditionalEffect.condition.accept(this, data)
+    }
+
+    override fun visitReturnsEffectDeclaration(returnsEffect: ConeReturnsEffectDeclaration, data: Nothing?) {
+        builder.append("Returns(")
+        returnsEffect.value.accept(this, data)
+        builder.append(")")
+    }
+
+    override fun visitCallsEffectDeclaration(callsEffect: ConeCallsEffectDeclaration, data: Nothing?) {
+        builder.append("CallsInPlace(")
+        callsEffect.valueParameterReference.accept(this, data)
+        builder.append(", ${callsEffect.kind})")
+    }
+
+    override fun visitLogicalBinaryOperationContractExpression(binaryLogicExpression: ConeBinaryLogicExpression, data: Nothing?) {
+        inBracketsIfNecessary(binaryLogicExpression, binaryLogicExpression.left) { binaryLogicExpression.left.accept(this, data) }
+        builder.append(" ${binaryLogicExpression.kind.token} ")
+        inBracketsIfNecessary(binaryLogicExpression, binaryLogicExpression.right) { binaryLogicExpression.right.accept(this, data) }
+    }
+
+    override fun visitLogicalNot(logicalNot: ConeLogicalNot, data: Nothing?) {
+        inBracketsIfNecessary(logicalNot, logicalNot.arg) { builder.append("!") }
+        logicalNot.arg.accept(this, data)
+    }
+
+    override fun visitIsInstancePredicate(isInstancePredicate: ConeIsInstancePredicate, data: Nothing?) {
+        isInstancePredicate.arg.accept(this, data)
+        builder.append(" ${if (isInstancePredicate.isNegated) "!" else ""}is ${isInstancePredicate.type}")
+    }
+
+    override fun visitIsNullPredicate(isNullPredicate: ConeIsNullPredicate, data: Nothing?) {
+        isNullPredicate.arg.accept(this, data)
+        builder.append(" ${if (isNullPredicate.isNegated) "!=" else "=="} null")
+    }
+
+    override fun visitConstantDescriptor(constantReference: ConeConstantReference, data: Nothing?) {
+        builder.append(constantReference.name)
+    }
+
+    override fun visitValueParameterReference(valueParameterReference: ConeValueParameterReference, data: Nothing?) {
+        builder.append(valueParameterReference.name)
+    }
+
+    private fun inBracketsIfNecessary(parent: ConeContractDescriptionElement, child: ConeContractDescriptionElement, block: () -> Unit) {
+        if (needsBrackets(parent, child)) {
+            builder.append("(")
+            block()
+            builder.append(")")
+        } else {
+            block()
+        }
+    }
+
+    private fun ConeContractDescriptionElement.isAtom(): Boolean =
+        this is VariableReference || this is ConstantReference || this is ConeIsNullPredicate || this is ConeIsInstancePredicate
+
+    private fun needsBrackets(parent: ConeContractDescriptionElement, child: ConeContractDescriptionElement): Boolean {
+        if (child.isAtom()) return false
+        if (parent is ConeLogicalNot) return true
+        return parent::class != child::class
+    }
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/contracts/description/ConeValues.kt

@@ -35,7 +35,7 @@ class ConeBooleanConstantReference private constructor(name: String) : ConeConst
  * Index of value parameter of function
  * -1 means that it is reference to extension receiver
  */
-open class ConeValueParameterReference(val parameterIndex: Int) : ConeContractDescriptionValue {
+open class ConeValueParameterReference(val parameterIndex: Int, val name: String) : ConeContractDescriptionValue {
     init {
         assert(parameterIndex >= -1)
     }
@@ -44,7 +44,7 @@ open class ConeValueParameterReference(val parameterIndex: Int) : ConeContractDe
         contractDescriptionVisitor.visitValueParameterReference(this, data)
 }
 
-class ConeBooleanValueParameterReference(parameterIndex: Int) : ConeValueParameterReference(parameterIndex), ConeBooleanExpression {
+class ConeBooleanValueParameterReference(parameterIndex: Int, name: String) : ConeValueParameterReference(parameterIndex, name), ConeBooleanExpression {
     override fun <R, D> accept(contractDescriptionVisitor: ConeContractDescriptionVisitor<R, D>, data: D): R =
         contractDescriptionVisitor.visitBooleanValueParameterReference(this, data)
 }