FIR: Support lambda inference from platform types

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/PostponedArguments.kt

@@ -106,7 +106,7 @@ private fun extraLambdaInfo(
     val isSuspend = expectedType?.isSuspendFunctionType ?: false
 
     val isFunctionSupertype =
-        expectedType != null && expectedType.isBuiltinFunctionalType//isNotNullOrNullableFunctionSupertype(expectedType)
+        expectedType != null && expectedType.lowerBoundIfFlexible().isBuiltinFunctionalType//isNotNullOrNullableFunctionSupertype(expectedType)
     val argumentAsFunctionExpression = argument//.safeAs<FunctionExpression>()
 
     val typeVariable = TypeVariableForLambdaReturnType(argument, "_L")
@@ -133,7 +133,9 @@ internal fun extractLambdaInfoFromFunctionalType(
     expectedTypeRef: FirTypeRef,
     argument: FirAnonymousFunction
 ): ResolvedLambdaAtom? {
-    if (expectedType == null || !expectedType.isBuiltinFunctionalType) return null
+    if (expectedType == null) return null
+    if (expectedType is ConeFlexibleType) return extractLambdaInfoFromFunctionalType(expectedType.lowerBound, expectedTypeRef, argument)
+    if (!expectedType.isBuiltinFunctionalType) return null
     val parameters = extractLambdaParameters(expectedType, argument)
 
     val argumentAsFunctionExpression = argument//.safeAs<FunctionExpression>()
@@ -193,4 +195,4 @@ class ResolvedLambdaAtom(
 
     override val inputTypes: Collection<ConeKotlinType> get() = receiver?.let { parameters + it } ?: parameters
     override val outputType: ConeKotlinType get() = returnType
-}
+}

compiler/fir/resolve/testData/diagnostics/j+k/FunctionTypeInJava.kt

@@ -0,0 +1,22 @@
+// WITH_RUNTIME
+// FILE: JavaClass.java
+public class JavaClass {
+    public static void foo1(kotlin.jvm.functions.Function0<Integer> x) {}
+    public static void foo2(kotlin.jvm.functions.Function1<Integer, String> x) {}
+    public static <T> void foo3(kotlin.jvm.functions.Function1<T, String> x, T y) {}
+}
+
+// FILE: main.kt
+
+fun main() {
+    JavaClass.foo1 { 123 }
+
+
+    JavaClass.foo2 { (it + 2).toString() }
+    JavaClass.foo2({ (it + 3).toString() })
+    val y = { x: Int -> x.toString() }
+    JavaClass.foo2(y)
+
+
+    JavaClass.foo3({ (it + 4).toString() }, 5)
+}

compiler/fir/resolve/testData/diagnostics/j+k/FunctionTypeInJava.txt

@@ -0,0 +1,24 @@
+FILE: main.kt
+    public final fun main(): R|kotlin/Unit| {
+        Q|JavaClass|.R|/JavaClass.foo1|(<L> = foo1@fun <anonymous>(): R|ft<kotlin/Int, kotlin/Int?>!| <kind=EXACTLY_ONCE>  {
+            Int(123)
+        }
+        )
+        Q|JavaClass|.R|/JavaClass.foo2|(<L> = foo2@fun <anonymous>(it: R|ft<kotlin/Int, kotlin/Int?>!|): R|ft<kotlin/String, kotlin/String?>!| <kind=EXACTLY_ONCE>  {
+            R|<local>/it|.R|kotlin/Int.plus|(Int(2)).R|kotlin/Any.toString|()
+        }
+        )
+        Q|JavaClass|.R|/JavaClass.foo2|(foo2@fun <anonymous>(it: R|ft<kotlin/Int, kotlin/Int?>!|): R|ft<kotlin/String, kotlin/String?>!| <kind=EXACTLY_ONCE>  {
+            R|<local>/it|.R|kotlin/Int.plus|(Int(3)).R|kotlin/Any.toString|()
+        }
+        )
+        lval y: R|kotlin/Function1<kotlin/Int, kotlin/String>| = fun <anonymous>(x: R|kotlin/Int|): R|kotlin/String| {
+            R|<local>/x|.R|kotlin/Any.toString|()
+        }
+
+        Q|JavaClass|.R|/JavaClass.foo2|(R|<local>/y|)
+        Q|JavaClass|.R|/JavaClass.foo3|<R|ft<kotlin/Int, kotlin/Int>|>(foo3@fun <anonymous>(it: R|ft<kotlin/Int, kotlin/Int>|): R|ft<kotlin/String, kotlin/String?>!| <kind=EXACTLY_ONCE>  {
+            R|<local>/it|.R|kotlin/Int.plus|(Int(4)).R|kotlin/Any.toString|()
+        }
+        , Int(5))
+    }

compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/AbstractFirDiagnosticsTest.kt

@@ -6,11 +6,16 @@
 package org.jetbrains.kotlin.fir
 
 import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.test.ConfigurationKind
 import org.jetbrains.kotlin.test.KotlinTestUtils
 import java.io.File
 
 abstract class AbstractFirDiagnosticsTest : AbstractFirDiagnosticsSmokeTest() {
 
+    override fun getConfigurationKind(): ConfigurationKind {
+        return ConfigurationKind.ALL
+    }
+
     override fun checkResultingFirFiles(
         firFiles: MutableList<FirFile>,
         testDataFile: File

compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsTestGenerated.java

@@ -46,6 +46,11 @@ public class FirDiagnosticsTestGenerated extends AbstractFirDiagnosticsTest {
             runTest("compiler/fir/resolve/testData/diagnostics/j+k/complexFlexibleInference.kt");
         }
 
+        @TestMetadata("FunctionTypeInJava.kt")
+        public void testFunctionTypeInJava() throws Exception {
+            runTest("compiler/fir/resolve/testData/diagnostics/j+k/FunctionTypeInJava.kt");
+        }
+
         @TestMetadata("KJKComplexHierarchy.kt")
         public void testKJKComplexHierarchy() throws Exception {
             runTest("compiler/fir/resolve/testData/diagnostics/j+k/KJKComplexHierarchy.kt");