KT-37986 Force boxing of inline class returned from function reference

KT-37998 Provide KotlinType for safe call

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

@@ -1033,13 +1033,19 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         );
 
         ClosureCodegen coroutineCodegen = CoroutineCodegenForLambda.create(this, descriptor, declaration, cv);
-        ClosureContext closureContext = descriptor.isSuspend() ? this.context.intoCoroutineClosure(
-                CoroutineCodegenUtilKt.getOrCreateJvmSuspendFunctionView(descriptor, state),
-                descriptor, this, state.getTypeMapper()
-        ) : this.context.intoClosure(descriptor, this, typeMapper);
-        ClosureCodegen closureCodegen = coroutineCodegen != null ? coroutineCodegen : new ClosureCodegen(
-                state, declaration, samType, closureContext, functionReferenceCall, strategy, parentCodegen, cv
-        );
+        ClosureContext closureContext =
+                descriptor.isSuspend()
+                ? this.context.intoCoroutineClosure(
+                        CoroutineCodegenUtilKt.getOrCreateJvmSuspendFunctionView(descriptor, state),
+                        descriptor, this, state.getTypeMapper()
+                )
+                : this.context.intoClosure(descriptor, this, typeMapper);
+        ClosureCodegen closureCodegen =
+                coroutineCodegen != null
+                ? coroutineCodegen
+                : new ClosureCodegen(
+                        state, declaration, samType, closureContext, functionReferenceCall, strategy, parentCodegen, cv
+                );
 
         closureCodegen.generate();
 
@@ -3399,7 +3405,7 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         StackValue result;
 
         if (!isPrimitive(expressionType(expression.getReceiverExpression()))) {
-            result = new StackValue.SafeFallback(type, ifnull, newReceiver);
+            result = new StackValue.SafeFallback(type, kotlinType, ifnull, newReceiver);
         } else {
             result = newReceiver;
         }
@@ -4363,7 +4369,6 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
 
         return StackValue.none();
     }
-
     @Override
     public StackValue visitDestructuringDeclaration(@NotNull KtDestructuringDeclaration multiDeclaration, StackValue receiver) {
         return initializeDestructuringDeclaration(multiDeclaration, false);

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

@@ -2308,8 +2308,8 @@ public abstract class StackValue {
 
         @Nullable private final Label ifNull;
 
-        public SafeFallback(@NotNull Type type, @Nullable Label ifNull, StackValue receiver) {
-            super(type, null, false, false, receiver, true);
+        public SafeFallback(@NotNull Type type, @Nullable KotlinType kotlinType, @Nullable Label ifNull, StackValue receiver) {
+            super(type, kotlinType, false, false, receiver, true);
             this.ifNull = ifNull;
         }
 

compiler/backend/src/org/jetbrains/kotlin/codegen/state/KotlinTypeMapper.kt

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.config.LanguageVersionSettingsImpl
 import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.impl.AnonymousFunctionDescriptor
 import org.jetbrains.kotlin.descriptors.impl.LocalVariableAccessorDescriptor
 import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
 import org.jetbrains.kotlin.descriptors.impl.TypeAliasConstructorDescriptor
@@ -41,10 +42,7 @@ import org.jetbrains.kotlin.load.java.lazy.descriptors.LazyJavaPackageFragment
 import org.jetbrains.kotlin.load.kotlin.*
 import org.jetbrains.kotlin.load.kotlin.incremental.IncrementalPackageFragmentProvider.IncrementalMultifileClassPackageFragment
 import org.jetbrains.kotlin.name.*
-import org.jetbrains.kotlin.psi.KtBinaryExpressionWithTypeRHS
-import org.jetbrains.kotlin.psi.KtExpression
-import org.jetbrains.kotlin.psi.KtFunctionLiteral
-import org.jetbrains.kotlin.psi.KtLambdaExpression
+import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getOutermostParenthesizerOrThis
 import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelector
 import org.jetbrains.kotlin.resolve.*
@@ -66,6 +64,7 @@ import org.jetbrains.kotlin.resolve.jvm.annotations.hasJvmDefaultAnnotation
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodGenericSignature
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodParameterKind
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodSignature
+import org.jetbrains.kotlin.resolve.source.KotlinSourceElement
 import org.jetbrains.kotlin.serialization.deserialization.descriptors.DescriptorWithContainerSource
 import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedCallableMemberDescriptor
 import org.jetbrains.kotlin.types.*
@@ -936,7 +935,20 @@ class KotlinTypeMapper @JvmOverloads constructor(
     private fun forceBoxedReturnType(descriptor: FunctionDescriptor): Boolean {
         if (isBoxMethodForInlineClass(descriptor)) return true
 
-        return isJvmPrimitiveOrInlineClass(descriptor.returnType!!) &&
+        val returnType = descriptor.returnType!!
+
+        // Crude hack to determine whether it is an AnonymousFunctionDescriptor created for callable reference.
+        // Ideally, we should force return type boxing for all anonymous functions returning an inline class value
+        // (so that the result is boxed properly, since technically it is a covariant override of a corresponding generic 'invoke').
+        // But, unfortunately, we can't do so right now, because it'd break binary compatibility for lambdas returning 'Result'.
+        if (descriptor is AnonymousFunctionDescriptor) {
+            val source = descriptor.source
+            if (source is KotlinSourceElement && source.psi is KtCallableReferenceExpression && returnType.isInlineClassType()) {
+                return true
+            }
+        }
+
+        return isJvmPrimitiveOrInlineClass(returnType) &&
                 getAllOverriddenDescriptors(descriptor).any { !isJvmPrimitiveOrInlineClass(it.returnType!!) }
     }