FIC: Support base version of conversions in JVM backend

Proper support for JVM backend will be in the further commmits

compiler/backend/src/org/jetbrains/kotlin/codegen/SamType.java

@@ -20,6 +20,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.codegen.state.TypeMapperUtilsKt;
+import org.jetbrains.kotlin.descriptors.ClassDescriptor;
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor;
 import org.jetbrains.kotlin.descriptors.SimpleFunctionDescriptor;
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor;
@@ -62,21 +63,25 @@ public class SamType {
     }
 
     @NotNull
-    public JavaClassDescriptor getJavaClassDescriptor() {
+    public ClassDescriptor getClassDescriptor() {
         ClassifierDescriptor classifier = type.getConstructor().getDeclarationDescriptor();
-        assert classifier instanceof JavaClassDescriptor : "Sam interface not a Java class: " + classifier;
-        return (JavaClassDescriptor) classifier;
+        assert classifier instanceof ClassDescriptor : "Sam/Fun interface not a class descriptor: " + classifier;
+        return (ClassDescriptor) classifier;
     }
 
     @NotNull
     public KotlinType getKotlinFunctionType() {
-        //noinspection ConstantConditions
-        return getJavaClassDescriptor().getDefaultFunctionTypeForSamInterface();
+        ClassDescriptor descriptor = getClassDescriptor();
+        if (descriptor instanceof JavaClassDescriptor) {
+            return ((JavaClassDescriptor) descriptor).getDefaultFunctionTypeForSamInterface();
+        }
+
+        return null;
     }
 
     @NotNull
     public SimpleFunctionDescriptor getOriginalAbstractMethod() {
-        return (SimpleFunctionDescriptor) SingleAbstractMethodUtils.getAbstractMembers(getJavaClassDescriptor()).get(0);
+        return (SimpleFunctionDescriptor) SingleAbstractMethodUtils.getAbstractMembers(getClassDescriptor()).get(0);
     }
 
     @Override

compiler/backend/src/org/jetbrains/kotlin/codegen/SamWrapperCodegen.java

@@ -82,7 +82,7 @@ public class SamWrapperCodegen {
         KotlinType functionType = samType.getKotlinFunctionType();
 
         ClassDescriptor classDescriptor = new ClassDescriptorImpl(
-                samType.getJavaClassDescriptor().getContainingDeclaration(),
+                samType.getClassDescriptor().getContainingDeclaration(),
                 fqName.shortName(),
                 Modality.FINAL,
                 ClassKind.CLASS,
@@ -132,7 +132,7 @@ public class SamWrapperCodegen {
     }
 
     private void generateConstructor(Type ownerType, Type functionType, ClassBuilder cv) {
-        MethodVisitor mv = cv.newMethod(JvmDeclarationOriginKt.OtherOrigin(samType.getJavaClassDescriptor()),
+        MethodVisitor mv = cv.newMethod(JvmDeclarationOriginKt.OtherOrigin(samType.getClassDescriptor()),
                                         visibility, "<init>", Type.getMethodDescriptor(Type.VOID_TYPE, functionType), null, null);
 
         if (state.getClassBuilderMode().generateBodies) {
@@ -198,7 +198,7 @@ public class SamWrapperCodegen {
                 "%s$sam%s$%s" + SAM_WRAPPER_SUFFIX,
                 outermostOwner.shortName().asString(),
                 (isInsideInline ? "$i" : ""),
-                DescriptorUtils.getFqNameSafe(samType.getJavaClassDescriptor()).asString().replace('.', '_')
+                DescriptorUtils.getFqNameSafe(samType.getClassDescriptor()).asString().replace('.', '_')
         );
         return outermostOwner.parent().child(Name.identifier(shortName));
     }

compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterfaceConversion.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: +NewInference +FunctionInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
+
+fun interface Foo {
+    fun invoke(): String
+}
+
+fun foo(f: Foo) = f.invoke()
+
+fun box(): String {
+    return foo { "OK" }
+}

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -13684,6 +13684,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             public void testBasicFunInterface() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterface.kt");
             }
+
+            @TestMetadata("basicFunInterfaceConversion.kt")
+            public void testBasicFunInterfaceConversion() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterfaceConversion.kt");
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/inlineClasses/functionNameMangling")

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -13684,6 +13684,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             public void testBasicFunInterface() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterface.kt");
             }
+
+            @TestMetadata("basicFunInterfaceConversion.kt")
+            public void testBasicFunInterfaceConversion() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterfaceConversion.kt");
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/inlineClasses/functionNameMangling")

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -12534,6 +12534,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             public void testBasicFunInterface() throws Exception {
                 runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterface.kt");
             }
+
+            @TestMetadata("basicFunInterfaceConversion.kt")
+            public void testBasicFunInterfaceConversion() throws Exception {
+                runTest("compiler/testData/codegen/box/inlineClasses/funInterface/basicFunInterfaceConversion.kt");
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/inlineClasses/functionNameMangling")