Improve CgIsInstance processing

Author: EgorkaKulikov

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/tree/CgMethodConstructor.kt

@@ -1229,13 +1229,13 @@ internal class CgMethodConstructor(val context: CgContext) : CgContextOwner by c
                                 if (containsReflectiveCall) {
                                     currentTryBlock.catch(InvocationTargetException::class.java.id) { exception ->
                                         testFrameworkManager.assertBoolean(
-                                            CgIsInstance(expectedErrorVariable, exception[getTargetException]())
+                                            expectedErrorVariable.isInstance(exception[getTargetException]())
                                         )
                                     }
                                 } else {
                                     currentTryBlock.catch(Throwable::class.java.id) { throwable ->
                                         testFrameworkManager.assertBoolean(
-                                            CgIsInstance(expectedErrorVariable, throwable)
+                                            expectedErrorVariable.isInstance(throwable)
                                         )
                                     }
                                 }

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/constructor/util/CgStatementConstructor.kt

@@ -58,6 +58,8 @@ import org.utbot.framework.plugin.api.util.objectArrayClassId
 import org.utbot.framework.plugin.api.util.objectClassId
 import fj.data.Either
 import org.utbot.framework.codegen.model.tree.CgArrayInitializer
+import org.utbot.framework.codegen.model.tree.CgIsInstance
+import org.utbot.framework.plugin.api.util.classClassId
 import java.lang.reflect.Constructor
 import java.lang.reflect.Method
 import kotlin.reflect.KFunction
@@ -116,6 +118,8 @@ interface CgStatementConstructor {
     fun CgTryCatch.catch(exception: ClassId, init: (CgVariable) -> Unit): CgTryCatch
     fun CgTryCatch.finally(init: () -> Unit): CgTryCatch
 
+    fun CgExpression.isInstance(typeExpr: CgExpression): CgIsInstance
+
     fun innerBlock(init: () -> Unit): CgInnerBlock
 
 //    fun CgTryCatchBuilder.statements(init: () -> Unit)
@@ -302,6 +306,14 @@ internal class CgStatementConstructorImpl(context: CgContext) :
         return this.copy(finally = finallyBlock)
     }
 
+    override fun CgExpression.isInstance(typeExpr: CgExpression): CgIsInstance {
+        require(this.type == classClassId) {
+            "isInstance method can be called on object with type $classClassId only, but actual type is ${this.type}"
+        }
+
+        return CgIsInstance(this, typeExpr)
+    }
+
     override fun innerBlock(init: () -> Unit): CgInnerBlock =
         CgInnerBlock(block(init)).also {
             currentBlock += it

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/tree/CgElement.kt

@@ -538,10 +538,13 @@ class CgTypeCast(
     override val type: ClassId = targetType
 }
 
+/**
+ * Represents [java.lang.Class.isInstance] method.
+ */
 class CgIsInstance(
-    val thisExpr: CgExpression,
-    val typeExpr: CgExpression,
-) : CgExpression {
+    val classExpression: CgExpression,
+    val value: CgExpression,
+): CgExpression {
     override val type: ClassId = booleanClassId
 }
 

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/model/visitor/CgAbstractRenderer.kt

@@ -426,9 +426,9 @@ internal abstract class CgAbstractRenderer(val context: CgContext, val printer:
     // isInstance check
 
     override fun visit(element: CgIsInstance) {
-        element.thisExpr.accept(this)
+        element.classExpression.accept(this)
         print(".isInstance(")
-        element.typeExpr.accept(this)
+        element.value.accept(this)
         print(")")
     }