Do necessary down casts when generating method calls

utbot-framework/src/main/kotlin/org/utbot/framework/codegen/services/access/CgCallableAccessManager.kt

@@ -29,6 +29,7 @@ import org.utbot.framework.codegen.domain.models.CgVariable
 import org.utbot.framework.codegen.services.access.CgCallableAccessManagerImpl.FieldAccessorSuitability.*
 import org.utbot.framework.codegen.tree.CgComponents.getStatementConstructorBy
 import org.utbot.framework.codegen.tree.CgComponents.getVariableConstructorBy
+import org.utbot.framework.codegen.tree.downcastIfNeeded
 import org.utbot.framework.codegen.tree.getAmbiguousOverloadsOf
 import org.utbot.framework.codegen.tree.importIfNeeded
 import org.utbot.framework.codegen.tree.isUtil
@@ -114,7 +115,11 @@ internal class CgCallableAccessManagerImpl(val context: CgContext) : CgCallableA
     override operator fun CgIncompleteMethodCall.invoke(vararg args: Any?): CgMethodCall {
         val resolvedArgs = args.resolve()
         val methodCall = if (method.canBeCalledWith(caller, resolvedArgs)) {
-            CgMethodCall(caller, method, resolvedArgs.guardedForDirectCallOf(method)).takeCallerFromArgumentsIfNeeded()
+            CgMethodCall(
+                caller = caller?.let { downcastIfNeeded(method.classId, caller) },
+                executableId = method,
+                arguments = resolvedArgs.guardedForDirectCallOf(method)
+            ).takeCallerFromArgumentsIfNeeded()
         } else {
             method.callWithReflection(caller, resolvedArgs)
         }
@@ -200,7 +205,8 @@ internal class CgCallableAccessManagerImpl(val context: CgContext) : CgCallableA
             // this executable can be called on builtin type
             this.type is BuiltinClassId && this.type in builtinCallersWithoutReflection -> true
 
-            else -> false
+            // receiver can be downcasted before call
+            else -> executable.isAccessibleFrom(testClassPackageName)
         }
 
     // For some builtin types we need to clarify

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

@@ -1159,7 +1159,7 @@ open class CgMethodConstructor(val context: CgContext) : CgContextOwner by conte
         } else if (context.codegenLanguage == CodegenLanguage.JAVA &&
             !jField.isStatic && canBeReadViaGetterFrom(context)
         ) {
-            CgMethodCall(variable, getter, emptyList())
+            variable[getter]()
         } else {
             utilsClassId[getFieldValue](variable, this.declaringClass.name, this.name)
         }

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

@@ -215,7 +215,7 @@ open class CgVariableConstructor(val context: CgContext) :
         } else if (context.codegenLanguage == CodegenLanguage.JAVA &&
             !field.isStatic && fieldId.canBeSetViaSetterFrom(context)
         ) {
-            +CgMethodCall(obj, fieldId.setter, listOf(valueForField))
+            +obj[fieldId.setter](valueForField)
         } else {
             // composite models must not have info about static fields, hence only non-static fields are set here
             +utilsClassId[setField](obj, fieldId.declaringClass.name, fieldId.name, valueForField)

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

@@ -291,6 +291,20 @@ internal fun CgContextOwner.typeCast(
     return CgTypeCast(denotableTargetType, expression, isSafetyCast)
 }
 
+/**
+ * Casts [expression] to [targetType] only if downcast is needed,
+ * e.g. this method will cast `Collection` to `Set`, but not vice-versa.
+ *
+ * @see typeCast
+ */
+internal fun CgContextOwner.downcastIfNeeded(
+    targetType: ClassId,
+    expression: CgExpression,
+    isSafetyCast: Boolean = false
+): CgExpression =
+    if (expression.type isSubtypeOf targetType) expression
+    else typeCast(targetType, expression, isSafetyCast)
+
 /**
  * Sets an element of arguments array in parameterized test,
  * if test framework represents arguments as array.