FIR: support adapted callable reference with vararg

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

@@ -228,11 +228,11 @@ internal object CheckCallableReferenceExpectedType : CheckerStage() {
         // callable reference.
         // TODO: should refer to LanguageVersionSettings.SuspendConversion
         val requireSuspendConversion = expectedType?.isSuspendFunctionType(callInfo.session) == true
-        // TODO: handle callable reference with vararg
         val resultingType: ConeKotlinType = when (fir) {
-            is FirFunction -> callInfo.session.createKFunctionType(
+            is FirFunction -> callInfo.session.createAdaptedKFunctionType(
+                callInfo.session,
                 fir, resultingReceiverType, returnTypeRef,
-                expectedParameterNumberWithReceiver = expectedType?.let { it.typeArguments.size - 1 },
+                expectedParameterTypes = expectedType?.typeArguments,
                 isSuspend = (fir as? FirSimpleFunction)?.isSuspend == true || requireSuspendConversion,
                 expectedReturnType = extractInputOutputTypesFromCallableReferenceExpectedType(expectedType, callInfo.session)?.outputType
             )
@@ -286,27 +286,67 @@ private fun createKPropertyType(
     )
 }
 
-private fun FirSession.createKFunctionType(
+private fun FirSession.createAdaptedKFunctionType(
+    session: FirSession,
     function: FirFunction<*>,
     receiverType: ConeKotlinType?,
     returnTypeRef: FirResolvedTypeRef,
-    expectedParameterNumberWithReceiver: Int?,
+    expectedParameterTypes: Array<out ConeTypeProjection>?,
     isSuspend: Boolean,
     expectedReturnType: ConeKotlinType?
 ): ConeKotlinType {
     // The similar adaptations: defaults and coercion-to-unit happen at org.jetbrains.kotlin.resolve.calls.components.CallableReferencesCandidateFactory.getCallableReferenceAdaptation
     val parameterTypes = mutableListOf<ConeKotlinType>()
-    val expectedParameterNumber = when {
-        expectedParameterNumberWithReceiver == null -> null
-        receiverType != null -> expectedParameterNumberWithReceiver - 1
-        else -> expectedParameterNumberWithReceiver
-    }
+    val shift = if (receiverType != null) 1 else 0
+    val expectedParameterNumber =
+        if (expectedParameterTypes == null) null
+        // Drop the last one: return type, and the first one: receiver type, if needed
+        else expectedParameterTypes.size - 1 - shift
+
+    fun ConeKotlinType?.isPotentiallyArray(): Boolean =
+        this != null && (this.arrayElementType() != null || this is ConeTypeVariableType)
+
+    var lastVarargParameter: FirValueParameter? = null
     for ((index, valueParameter) in function.valueParameters.withIndex()) {
-        if (expectedParameterNumber == null ||
-            index < expectedParameterNumber ||
-            (valueParameter.defaultValue == null && !valueParameter.isVararg)
-        ) {
+        // Update the last vararg parameter in preparation for adaptation.
+        if (valueParameter.isVararg) {
+            lastVarargParameter = valueParameter
+        }
+        // Pack value parameters until the expected parameter number is met.
+        if (expectedParameterNumber == null || index < expectedParameterNumber) {
+            // But, if the value parameter is vararg, make sure it matches with the expected parameter type.
+            if (expectedParameterTypes != null && valueParameter.isVararg) {
+                val expectedParameterType = (expectedParameterTypes[index + shift] as? ConeKotlinTypeProjection)?.type
+                if (!expectedParameterType.isPotentiallyArray()) {
+                    // Expect an element. Will spread vararg parameter later.
+                    continue
+                }
+            }
             parameterTypes += valueParameter.returnTypeRef.coneType
+            continue
+        }
+        // After expected parameters are fulfilled, a value parameter which doesn't have a default value or isn't vararg should be added to
+        // the resulting type (so that it can reject incompatible function reference). In either case, we can't assume no actual arguments
+        // are given.
+        if (valueParameter.defaultValue == null && !valueParameter.isVararg) {
+            parameterTypes += valueParameter.returnTypeRef.coneType
+        }
+    }
+
+    // If a function with vararg is passed to a place where a spread of elements is expected, we can adapt the function reference to
+    // literally spread such vararg argument. E.g., foo(vararg xs: Char): String => bar(::foo) where bar(f: (Char, Char) -> String)
+    if (expectedParameterNumber != null && expectedParameterTypes != null && parameterTypes.size < expectedParameterNumber && lastVarargParameter != null) {
+        val varargArrayType = lastVarargParameter.returnTypeRef.coneType
+        val varargElementType = varargArrayType.varargElementType(session)
+        val expectedParameterType = (expectedParameterTypes[parameterTypes.size + shift] as? ConeKotlinTypeProjection)?.type
+        // Expect an array or potentially array (i.e., type variable). Pass vararg parameter as-is.
+        if (expectedParameterType.isPotentiallyArray()) {
+            parameterTypes += varargArrayType
+        } else {
+            // Expect an element. Spread vararg parameter.
+            while (parameterTypes.size < expectedParameterNumber) {
+                parameterTypes += varargElementType
+            }
         }
     }
 
@@ -317,7 +357,8 @@ private fun FirSession.createKFunctionType(
             returnTypeRef.type
 
     return createFunctionalType(
-        parameterTypes, receiverType = receiverType,
+        parameterTypes,
+        receiverType = receiverType,
         rawReturnType = returnType,
         isKFunctionType = true,
         isSuspend = isSuspend

compiler/testData/codegen/box/callableReference/adaptedReferences/innerConstructorWithVararg.kt

@@ -1,6 +1,4 @@
 // !LANGUAGE: +NewInference +FunctionReferenceWithDefaultValueAsOtherType
-// IGNORE_BACKEND_FIR: JVM_IR
-
 
 class Outer(val o: String) {
     inner class Inner1(val i: Int, vararg v: String) {

compiler/testData/codegen/box/callableReference/adaptedReferences/largeVararg.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +NewInference
-// IGNORE_BACKEND_FIR: JVM_IR
 
 fun foo(
     f: (

compiler/testData/codegen/box/callableReference/adaptedReferences/localFunctionWithDefault.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +NewInference +FunctionReferenceWithDefaultValueAsOtherType
-// IGNORE_BACKEND_FIR: JVM_IR
 
 fun call0(f: (String) -> String, x: String): String = f(x)
 fun call1(f: (String, String) -> String, x: String, y: String): String = f(x, y)

compiler/testData/codegen/box/callableReference/adaptedReferences/varargViewedAsPrimitiveArray.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // !LANGUAGE: +NewInference
 
 fun sum(vararg args: Int): Int {

compiler/testData/codegen/box/callableReference/adaptedReferences/varargWithDefaultValue.kt

@@ -1,5 +1,4 @@
 // !LANGUAGE: +NewInference +FunctionReferenceWithDefaultValueAsOtherType
-// IGNORE_BACKEND_FIR: JVM_IR
 
 fun foo(x: Int, s: Int, vararg y: CharSequence = arrayOf("Aaa")): String =
         if (y.size == s && y[0].length == x) "OK" else "Fail"

compiler/testData/codegen/box/callableReference/serializability/adaptedReferences.kt

@@ -1,5 +1,4 @@
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
 // WITH_REFLECT
 
 import java.io.*

compiler/testData/diagnostics/tests/callableReference/genericCallWithReferenceAgainstVararg.fir.kt

@@ -7,7 +7,7 @@ fun test(i: IntArray) {
     myLet(::foo)
     <!INAPPLICABLE_CANDIDATE!>myLet<!><Int>(<!UNRESOLVED_REFERENCE!>::foo<!>)
     myLet<IntArray>(::foo)
-    <!INAPPLICABLE_CANDIDATE!>myLetExplicit1<!>(<!UNRESOLVED_REFERENCE!>::foo<!>)
+    myLetExplicit1(::foo)
     myLetExplicit2(::foo)
 }
 

compiler/testData/diagnostics/tests/callableReference/referenceAdaptationCompatibility.fir.kt

@@ -36,7 +36,7 @@ object Test3 {
 
         fun test() {
             val result = foo(::bar)
-            <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int")!>result<!>
+            <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String")!>result<!>
         }
     }
 }

compiler/testData/diagnostics/tests/callableReference/referenceAdaptationHasDependencyOnApi14.fir.kt

@@ -12,7 +12,7 @@ fun allOfTheAbove(f: (A) -> Unit): Any = f
 
 fun test() {
     coercionToUnit(A::foo)
-    <!INAPPLICABLE_CANDIDATE!>varargToElement<!>(<!UNRESOLVED_REFERENCE!>A::foo<!>)
+    varargToElement(A::foo)
     defaultAndVararg(A::foo)
     allOfTheAbove(A::foo)
 }

compiler/testData/diagnostics/tests/callableReference/resolve/withVararg.fir.kt

@@ -6,5 +6,5 @@ fun foo(i: Int) {}
 
 val fn1: (Int) -> Unit = ::foo
 val fn2: (IntArray) -> Unit = ::foo
-val fn3: (Int, Int) -> Unit = <!UNRESOLVED_REFERENCE!>::foo<!>
+val fn3: (Int, Int) -> Unit = ::foo
 val fn4: (Array<String>) -> Unit = ::foo

compiler/testData/diagnostics/tests/suspendConversion/suspendConversionWithReferenceAdaptation.fir.kt

@@ -1,21 +0,0 @@
-// !LANGUAGE: +SuspendConversion
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-
-fun unitCoercion(f: suspend () -> Unit) {}
-fun foo(): Int = 0
-
-fun defaults(f: suspend (Int) -> String) {}
-fun bar(i: Int, l: Long = 42L): String = ""
-
-fun varargs(f: suspend (Int, Int, Int) -> String) {}
-fun baz(vararg ints: Int): String = ""
-
-fun unitCoercionAndDefaults(f: suspend () -> Unit) {}
-fun all(s: String = ""): Int = 0
-
-fun test() {
-    unitCoercion(::foo)
-    defaults(::bar)
-    <!INAPPLICABLE_CANDIDATE!>varargs<!>(<!UNRESOLVED_REFERENCE!>::baz<!>)
-    unitCoercionAndDefaults(::all)
-}

compiler/testData/diagnostics/tests/suspendConversion/suspendConversionWithReferenceAdaptation.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +SuspendConversion
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 

compiler/testData/diagnostics/tests/varargs/varargViewedAsArray.fir.kt

@@ -17,13 +17,13 @@ fun useMixedStringArgs3(fn: (String, Array<String>, String) -> Unit) = fn("foo",
 fun useTwoStringArrays(fn: (Array<String>, Array<String>) -> Unit) = fn(arrayOf("foo", "bar"), arrayOf("baz", "boo"))
 
 fun test() {
-    <!INAPPLICABLE_CANDIDATE!>useStrings<!>(<!UNRESOLVED_REFERENCE!>::stringVararg<!>)
+    useStrings(::stringVararg)
     useStringArray(::stringVararg)
     useIntArray(::numberVararg)
     usePrimitiveIntArray(::intVararg)
     <!INAPPLICABLE_CANDIDATE!>useIntArray<!>(<!UNRESOLVED_REFERENCE!>::intVararg<!>)
     <!INAPPLICABLE_CANDIDATE!>useMixedStringArgs1<!>(<!UNRESOLVED_REFERENCE!>::stringVararg<!>)
-    <!INAPPLICABLE_CANDIDATE!>useMixedStringArgs2<!>(<!UNRESOLVED_REFERENCE!>::stringVararg<!>)
+    useMixedStringArgs2(::stringVararg)
     <!INAPPLICABLE_CANDIDATE!>useMixedStringArgs3<!>(<!UNRESOLVED_REFERENCE!>::stringVararg<!>)
-    <!INAPPLICABLE_CANDIDATE!>useTwoStringArrays<!>(<!UNRESOLVED_REFERENCE!>::stringVararg<!>)
+    useTwoStringArrays(::stringVararg)
 }

compiler/testData/ir/irText/expressions/callableReferences/adaptedWithCoercionToUnit.fir.txt

@@ -37,5 +37,5 @@ FILE fqName:<root> fileName:/adaptedWithCoercionToUnit.kt
   FUN name:testV1 visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testV1 (): kotlin.Unit declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /useUnit1>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: fnv>#' type=IrErrorType
+        CALL 'public final fun useUnit1 (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun fnv (vararg xs: kotlin.Int): kotlin.Int declared in <root>' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>

compiler/testData/ir/irText/expressions/callableReferences/constructorWithAdaptedArguments.fir.txt

@@ -69,16 +69,18 @@ FILE fqName:<root> fileName:/constructorWithAdaptedArguments.kt
   FUN name:testConstructor visibility:public modality:FINAL <> () returnType:kotlin.Any
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testConstructor (): kotlin.Any declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Any
-          ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: C>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Any>): kotlin.Any declared in <root>' type=kotlin.Any origin=null
+          fn: FUNCTION_REFERENCE 'public constructor <init> (vararg xs: kotlin.Int) [primary] declared in <root>.C' type=kotlin.reflect.KFunction1<kotlin.Int, <root>.C> origin=null reflectionTarget=<same>
   FUN name:testInnerClassConstructor visibility:public modality:FINAL <> (outer:<root>.Outer) returnType:kotlin.Any
     VALUE_PARAMETER name:outer index:0 type:<root>.Outer
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testInnerClassConstructor (outer: <root>.Outer): kotlin.Any declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Any
-          ERROR_CALL 'Unsupported callable reference: R|<local>/outer|::<Unresolved reference: Inner>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Any>): kotlin.Any declared in <root>' type=kotlin.Any origin=null
+          fn: FUNCTION_REFERENCE 'public constructor <init> (vararg xs: kotlin.Int) [primary] declared in <root>.Outer.Inner' type=kotlin.reflect.KFunction1<kotlin.Int, <root>.Outer.Inner> origin=null reflectionTarget=<same>
+            $this: GET_VAR 'outer: <root>.Outer declared in <root>.testInnerClassConstructor' type=<root>.Outer origin=null
   FUN name:testInnerClassConstructorCapturingOuter visibility:public modality:FINAL <> () returnType:kotlin.Any
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testInnerClassConstructorCapturingOuter (): kotlin.Any declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Any
-          ERROR_CALL 'Unsupported callable reference: R|/Outer.Outer|()::<Unresolved reference: Inner>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Any>): kotlin.Any declared in <root>' type=kotlin.Any origin=null
+          fn: FUNCTION_REFERENCE 'public constructor <init> (vararg xs: kotlin.Int) [primary] declared in <root>.Outer.Inner' type=kotlin.reflect.KFunction1<kotlin.Int, <root>.Outer.Inner> origin=null reflectionTarget=<same>
+            $this: CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.Outer' type=<root>.Outer origin=null

compiler/testData/ir/irText/expressions/callableReferences/suspendConversion.fir.txt

@@ -82,8 +82,12 @@ FILE fqName:<root> fileName:/suspendConversion.kt
               CALL 'public final fun foo2 (vararg xs: kotlin.Int): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
   FUN name:testWithVarargMapped visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /useSuspendInt>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: foo2>#' type=IrErrorType
+      CALL 'public final fun useSuspendInt (fn: kotlin.coroutines.SuspendFunction1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        fn: FUN_EXPR type=kotlin.coroutines.SuspendFunction1<kotlin.Int, kotlin.Unit> origin=ADAPTED_FUNCTION_REFERENCE
+          FUN ADAPTER_FOR_CALLABLE_REFERENCE name:foo2 visibility:local modality:FINAL <> (p0:kotlin.Int) returnType:kotlin.Unit [suspend]
+            VALUE_PARAMETER ADAPTER_PARAMETER_FOR_CALLABLE_REFERENCE name:p0 index:0 type:kotlin.Int
+            BLOCK_BODY
+              CALL 'public final fun foo2 (vararg xs: kotlin.Int): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
   FUN name:testWithCoercionToUnit visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       CALL 'public final fun useSuspend (fn: kotlin.coroutines.SuspendFunction0<kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null

compiler/testData/ir/irText/expressions/callableReferences/unboundMemberReferenceWithAdaptedArguments.fir.txt

@@ -59,14 +59,16 @@ FILE fqName:<root> fileName:/unboundMemberReferenceWithAdaptedArguments.kt
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any
   FUN name:testUnbound visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use1>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: Q|A|::<Unresolved reference: foo>#' type=IrErrorType
+      CALL 'public final fun use1 (fn: kotlin.Function2<<root>.A, kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        fn: FUNCTION_REFERENCE 'public open fun foo (vararg xs: kotlin.Int): kotlin.Int declared in <root>.A' type=kotlin.reflect.KFunction2<<root>.A, kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
   FUN name:testBound visibility:public modality:FINAL <> (a:<root>.A) returnType:kotlin.Unit
     VALUE_PARAMETER name:a index:0 type:<root>.A
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use2>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: R|<local>/a|::<Unresolved reference: foo>#' type=IrErrorType
+      CALL 'public final fun use2 (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        fn: FUNCTION_REFERENCE 'public open fun foo (vararg xs: kotlin.Int): kotlin.Int declared in <root>.A' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+          $this: GET_VAR 'a: <root>.A declared in <root>.testBound' type=<root>.A origin=null
   FUN name:testObject visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use2>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: Q|Obj|::<Unresolved reference: foo>#' type=IrErrorType
+      CALL 'public final fun use2 (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        fn: FUNCTION_REFERENCE 'public final fun foo (vararg xs: kotlin.Int): kotlin.Int declared in <root>.Obj' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+          $this: GET_OBJECT 'CLASS OBJECT name:Obj modality:FINAL visibility:public superTypes:[<root>.A]' type=<root>.Obj

compiler/testData/ir/irText/expressions/callableReferences/withAdaptationForSam.fir.txt

@@ -27,5 +27,6 @@ FILE fqName:<root> fileName:/withAdaptationForSam.kt
         CONST Int type=kotlin.Int value=42
   FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /useFoo>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: withVararg>#' type=IrErrorType
+      CALL 'public final fun useFoo (foo: <root>.IFoo): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        foo: TYPE_OP type=<root>.IFoo origin=SAM_CONVERSION typeOperand=<root>.IFoo
+          FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.Int declared in <root>' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>

compiler/testData/ir/irText/expressions/callableReferences/withAdaptedArguments.fir.txt

@@ -71,8 +71,8 @@ FILE fqName:<root> fileName:/withAdaptedArguments.kt
   FUN name:testVararg visibility:public modality:FINAL <> () returnType:kotlin.String
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testVararg (): kotlin.String declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.String
-          ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: fnWithVarargs>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.String>): kotlin.String declared in <root>' type=kotlin.String origin=null
+          fn: FUNCTION_REFERENCE 'public final fun fnWithVarargs (vararg xs: kotlin.Int): kotlin.String declared in <root>' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.String> origin=null reflectionTarget=<same>
   FUN name:testCoercionToUnit visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testCoercionToUnit (): kotlin.Unit declared in <root>'
@@ -81,8 +81,9 @@ FILE fqName:<root> fileName:/withAdaptedArguments.kt
   FUN name:testImportedObjectMember visibility:public modality:FINAL <> () returnType:kotlin.String
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testImportedObjectMember (): kotlin.String declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.String
-          ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: importedObjectMemberWithVarargs>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.String>): kotlin.String declared in <root>' type=kotlin.String origin=null
+          fn: FUNCTION_REFERENCE 'public final fun importedObjectMemberWithVarargs (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.String> origin=null reflectionTarget=<same>
+            $this: GET_OBJECT 'CLASS OBJECT name:Host modality:FINAL visibility:public superTypes:[kotlin.Any]' type=<root>.Host
   FUN name:testDefault0 visibility:public modality:FINAL <> () returnType:kotlin.String
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun testDefault0 (): kotlin.String declared in <root>'

compiler/testData/ir/irText/expressions/callableReferences/withArgumentAdaptationAndReceiver.fir.txt

@@ -20,33 +20,38 @@ FILE fqName:<root> fileName:/withArgumentAdaptationAndReceiver.kt
     FUN name:testImplicitThis visibility:public modality:FINAL <> ($this:<root>.Host) returnType:kotlin.Unit
       $this: VALUE_PARAMETER name:<this> type:<root>.Host
       BLOCK_BODY
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: withVararg>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+            $this: GET_VAR '<this>: <root>.Host declared in <root>.Host.testImplicitThis' type=<root>.Host origin=null
     FUN name:testBoundReceiverLocalVal visibility:public modality:FINAL <> ($this:<root>.Host) returnType:kotlin.Unit
       $this: VALUE_PARAMETER name:<this> type:<root>.Host
       BLOCK_BODY
         VAR name:h type:<root>.Host [val]
           CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.Host' type=<root>.Host origin=null
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: R|<local>/h|::<Unresolved reference: withVararg>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+            $this: GET_VAR 'val h: <root>.Host [val] declared in <root>.Host.testBoundReceiverLocalVal' type=<root>.Host origin=null
     FUN name:testBoundReceiverLocalVar visibility:public modality:FINAL <> ($this:<root>.Host) returnType:kotlin.Unit
       $this: VALUE_PARAMETER name:<this> type:<root>.Host
       BLOCK_BODY
         VAR name:h type:<root>.Host [var]
           CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.Host' type=<root>.Host origin=null
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: R|<local>/h|::<Unresolved reference: withVararg>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+            $this: GET_VAR 'var h: <root>.Host [var] declared in <root>.Host.testBoundReceiverLocalVar' type=<root>.Host origin=null
     FUN name:testBoundReceiverParameter visibility:public modality:FINAL <> ($this:<root>.Host, h:<root>.Host) returnType:kotlin.Unit
       $this: VALUE_PARAMETER name:<this> type:<root>.Host
       VALUE_PARAMETER name:h index:0 type:<root>.Host
       BLOCK_BODY
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: R|<local>/h|::<Unresolved reference: withVararg>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+            $this: GET_VAR 'h: <root>.Host declared in <root>.Host.testBoundReceiverParameter' type=<root>.Host origin=null
     FUN name:testBoundReceiverExpression visibility:public modality:FINAL <> ($this:<root>.Host) returnType:kotlin.Unit
       $this: VALUE_PARAMETER name:<this> type:<root>.Host
       BLOCK_BODY
-        ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /use>#' type=kotlin.Unit
-          ERROR_CALL 'Unsupported callable reference: R|/Host.Host|()::<Unresolved reference: withVararg>#' type=IrErrorType
+        CALL 'public final fun use (fn: kotlin.Function1<kotlin.Int, kotlin.Unit>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+          fn: FUNCTION_REFERENCE 'public final fun withVararg (vararg xs: kotlin.Int): kotlin.String declared in <root>.Host' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>
+            $this: CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.Host' type=<root>.Host origin=null
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean [fake_override,operator]
       overridden:
         public open fun equals (other: kotlin.Any?): kotlin.Boolean [operator] declared in kotlin.Any

compiler/testData/ir/irText/expressions/callableReferences/withVarargViewedAsArray.fir.txt

@@ -60,8 +60,8 @@ FILE fqName:<root> fileName:/withVarargViewedAsArray.kt
     BLOCK_BODY
   FUN name:testPlainArgs visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /usePlainArgs>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: sum>#' type=IrErrorType
+      CALL 'public final fun usePlainArgs (fn: kotlin.Function2<kotlin.Int, kotlin.Int, kotlin.Int>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        fn: FUNCTION_REFERENCE 'public final fun sum (vararg args: kotlin.Int): kotlin.Int declared in <root>' type=kotlin.reflect.KFunction2<kotlin.Int, kotlin.Int, kotlin.Int> origin=null reflectionTarget=<same>
   FUN name:testPrimitiveArrayAsVararg visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       CALL 'public final fun usePrimitiveArray (fn: kotlin.Function1<kotlin.IntArray, kotlin.Int>): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null

compiler/testData/ir/irText/expressions/funInterface/samConversionInVarargs.fir.txt

@@ -59,5 +59,6 @@ FILE fqName:<root> fileName:/samConversionInVarargs.kt
         CONST String type=kotlin.String value=""
   FUN name:testAdaptedCR visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
-      ERROR_CALL 'Unresolved reference: <Inapplicable(INAPPLICABLE): /useVararg>#' type=kotlin.Unit
-        ERROR_CALL 'Unsupported callable reference: ::<Unresolved reference: withVarargOfInt>#' type=IrErrorType
+      CALL 'public final fun useVararg (vararg foos: <root>.IFoo): kotlin.Unit declared in <root>' type=kotlin.Unit origin=null
+        foos: VARARG type=kotlin.Array<out <root>.IFoo> varargElementType=<root>.IFoo
+          FUNCTION_REFERENCE 'public final fun withVarargOfInt (vararg xs: kotlin.Int): kotlin.String declared in <root>' type=kotlin.reflect.KFunction1<kotlin.Int, kotlin.Unit> origin=null reflectionTarget=<same>

compiler/tests-spec/testData/diagnostics/linked/overload-resolution/resolving-callable-references/bidirectional-resolution-for-callable-calls/p-3/pos/1.4.fir.kt

@@ -28,10 +28,10 @@ class Case2() {
     }
 
     fun case() {
-        <!NONE_APPLICABLE!>foo<!>(<!DEBUG_INFO_EXPRESSION_TYPE("Type is unknown"), UNRESOLVED_REFERENCE!>::invoke<!>, <!DEBUG_INFO_EXPRESSION_TYPE("Type is unknown"), UNRESOLVED_REFERENCE!>::invoke<!>)
-        <!NONE_APPLICABLE!>foo<!>(<!UNRESOLVED_REFERENCE!>::invoke<!>, <!UNRESOLVED_REFERENCE!>::invoke<!>)
-        <!DEBUG_INFO_CALL("fqName: fqName is unknown; typeCall: unresolved")!><!NONE_APPLICABLE!>foo<!>(<!UNRESOLVED_REFERENCE!>::invoke<!>, <!UNRESOLVED_REFERENCE!>::invoke<!>)<!>
-        <!DEBUG_INFO_EXPRESSION_TYPE("ERROR CLASS: Ambiguity: foo, [/Case2.foo, /Case2.foo]")!><!NONE_APPLICABLE!>foo<!>(<!UNRESOLVED_REFERENCE!>::invoke<!>, <!UNRESOLVED_REFERENCE!>::invoke<!>)<!>
+        foo(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.reflect.KFunction1<kotlin.Int, kotlin.String>")!>::invoke<!>, <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.reflect.KFunction1<kotlin.Int, kotlin.String>")!>::invoke<!>)
+        foo(::invoke, ::invoke)
+        <!DEBUG_INFO_CALL("fqName: Case2.foo; typeCall: function")!>foo(::invoke, ::invoke)<!>
+        <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String")!>foo(::invoke, ::invoke)<!>
     }
 
     fun foo(vararg x: (Int)->Any): String = TODO() // (1.1)