[FIR] Implement FUNCTION_EXPECTED

compiler/fir/analysis-tests/testData/resolve/expresssions/invoke/threeReceivers.fir.txt

@@ -32,7 +32,7 @@ FILE: threeReceivers.kt
             }
 
         public final fun R|FooBar|.chk(buz: R|Buz|): R|kotlin/Unit| {
-            R|<local>/buz|.<Unresolved name: foobar>#()
+            R|<local>/buz|.<Expression 'foobar' of type 'Bar' cannot be invoked as a function>#()
         }
 
     }

compiler/fir/analysis-tests/testData/resolve/expresssions/invoke/threeReceivers.kt

@@ -17,6 +17,6 @@ class Foo {
         // this@Foo is dispatch receiver of foobar
         // Foo/foobar is dispatch receiver of invoke
         // this@chk is extension receiver of invoke
-        buz.<!UNRESOLVED_REFERENCE!>foobar<!>()
+        buz.<!FUNCTION_EXPECTED!>foobar<!>()
     }
 }

compiler/fir/analysis-tests/testData/resolve/problems/inaccessibleJavaGetter.fir.txt

@@ -28,5 +28,5 @@ FILE: test.kt
         lval res1: R|kotlin/String| = R|<local>/descriptor|.R|/WrappedPropertyDescriptor.setter|
         lval res2: <ERROR TYPE REF: Unresolved name: getSetter> = R|<local>/descriptor|.<Unresolved name: getSetter>#()
         lval res3: R|kotlin/Boolean| = R|<local>/descriptor|.R|/WrappedPropertyDescriptor.isDelegated|
-        lval res4: <ERROR TYPE REF: Unresolved name: isDelegated> = R|<local>/descriptor|.<Unresolved name: isDelegated>#()
+        lval res4: <ERROR TYPE REF: Expression 'isDelegated' of type 'kotlin/Boolean' cannot be invoked as a function> = R|<local>/descriptor|.<Expression 'isDelegated' of type 'kotlin/Boolean' cannot be invoked as a function>#()
     }

compiler/fir/analysis-tests/testData/resolve/problems/inaccessibleJavaGetter.kt

@@ -22,5 +22,5 @@ fun test() {
     val res1 = descriptor.setter
     val res2 = descriptor.<!UNRESOLVED_REFERENCE!>getSetter<!>() // Should be error
     val res3 = descriptor.isDelegated
-    val res4 = descriptor.<!UNRESOLVED_REFERENCE!>isDelegated<!>() // Should be error
+    val res4 = descriptor.<!FUNCTION_EXPECTED!>isDelegated<!>() // Should be error
 }

compiler/fir/analysis-tests/testData/resolve/properties/syntheticPropertiesForJavaAnnotations.fir.txt

@@ -1,5 +1,5 @@
 FILE: main.kt
     public final fun test(ann: R|Ann|): R|kotlin/Unit| {
         R|<local>/ann|.R|/Ann.value|
-        R|<local>/ann|.<Unresolved name: value>#()
+        R|<local>/ann|.<Expression 'value' of type 'kotlin/String' cannot be invoked as a function>#()
     }

compiler/fir/analysis-tests/testData/resolve/properties/syntheticPropertiesForJavaAnnotations.kt

@@ -3,12 +3,12 @@
 // FILE: Ann.java
 
 public @interface Ann {
-    String value()
+    String value();
 }
 
 // FILE: main.kt
 
 fun test(ann: Ann) {
     ann.value
-    ann.<!UNRESOLVED_REFERENCE!>value<!>() // should be an error
+    ann.<!FUNCTION_EXPECTED!>value<!>() // should be an error
 }

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -120,6 +120,10 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         }
         val ILLEGAL_SELECTOR by error<PsiElement>()
         val NO_RECEIVER_ALLOWED by error<PsiElement>()
+        val FUNCTION_EXPECTED by error<PsiElement>(PositioningStrategy.REFERENCED_NAME_BY_QUALIFIED) {
+            parameter<String>("expression")
+            parameter<ConeKotlinType>("type")
+        }
     }
 
     val SUPER by object : DiagnosticGroup("Super") {

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -133,6 +133,7 @@ object FirErrors {
     val FUNCTION_CALL_EXPECTED by error2<PsiElement, String, Boolean>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
     val ILLEGAL_SELECTOR by error0<PsiElement>()
     val NO_RECEIVER_ALLOWED by error0<PsiElement>()
+    val FUNCTION_EXPECTED by error2<PsiElement, String, ConeKotlinType>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
 
     // Super
     val SUPER_IS_NOT_AN_EXPRESSION by error0<PsiElement>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt

@@ -177,6 +177,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FINAL_UPPER_BOUND
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FORBIDDEN_VARARG_PARAMETER_TYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUNCTION_CALL_EXPECTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUNCTION_DECLARATION_WITH_NO_NAME
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUNCTION_EXPECTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUN_INTERFACE_ABSTRACT_METHOD_WITH_DEFAULT_VALUE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUN_INTERFACE_ABSTRACT_METHOD_WITH_TYPE_PARAMETERS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.FUN_INTERFACE_CANNOT_HAVE_ABSTRACT_PROPERTIES
@@ -434,6 +435,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_MODIFIER_TA
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_NUMBER_OF_TYPE_ARGUMENTS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_SETTER_PARAMETER_TYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.WRONG_SETTER_RETURN_TYPE
+import org.jetbrains.kotlin.name.StandardClassIds
 
 @Suppress("unused")
 class FirDefaultErrorMessages {
@@ -496,6 +498,10 @@ class FirDefaultErrorMessages {
             )
             map.put(CREATING_AN_INSTANCE_OF_ABSTRACT_CLASS, "Cannot create an instance of an abstract class")
             map.put(FUNCTION_CALL_EXPECTED, "Function invocation ''{0}({1})'' expected", TO_STRING, FUNCTION_PARAMETERS)
+            map.put(
+                FUNCTION_EXPECTED,
+                "Expression ''{0}'' of type {1} cannot be invoked as a function. The function 'invoke()' is not found", TO_STRING, RENDER_TYPE
+            )
             map.put(ILLEGAL_SELECTOR, "The expression cannot be a selector (occur after a dot)")
             map.put(NO_RECEIVER_ALLOWED, "No receiver can be passed to this function or property")
 

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt

@@ -41,6 +41,7 @@ private fun ConeDiagnostic.toFirDiagnostic(
     is ConeUnresolvedNameError -> FirErrors.UNRESOLVED_REFERENCE.createOn(source, this.name.asString())
     is ConeUnresolvedQualifierError -> FirErrors.UNRESOLVED_REFERENCE.createOn(source, this.qualifier)
     is ConeFunctionCallExpectedError -> FirErrors.FUNCTION_CALL_EXPECTED.createOn(source, this.name.asString(), this.hasValueParameters)
+    is ConeFunctionExpectedError -> FirErrors.FUNCTION_EXPECTED.createOn(source, this.expression, this.type)
     is ConeHiddenCandidateError -> FirErrors.INVISIBLE_REFERENCE.createOn(source, this.candidateSymbol)
     is ConeAmbiguityError -> when {
         applicability.isSuccess -> FirErrors.OVERLOAD_RESOLUTION_AMBIGUITY.createOn(source, this.candidates.map { it.symbol })

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.fir.resolve.*
 import org.jetbrains.kotlin.fir.resolve.calls.*
 import org.jetbrains.kotlin.fir.resolve.calls.tower.FirTowerResolver
 import org.jetbrains.kotlin.fir.resolve.calls.tower.TowerResolveManager
+import org.jetbrains.kotlin.fir.resolve.dfa.symbol
 import org.jetbrains.kotlin.fir.resolve.diagnostics.*
 import org.jetbrains.kotlin.fir.resolve.inference.ResolvedCallableReferenceAtom
 import org.jetbrains.kotlin.fir.resolve.inference.inferenceComponents
@@ -84,6 +85,14 @@ class FirCallResolver(
         val name = functionCall.calleeReference.name
         val result = collectCandidates(functionCall, name)
 
+        var forceCandidates: Collection<Candidate>? = null
+        if (result.candidates.isEmpty()) {
+            val newResult = collectCandidates(functionCall, name, CallKind.VariableAccess)
+            if (newResult.candidates.isNotEmpty()) {
+                forceCandidates = newResult.candidates
+            }
+        }
+
         val nameReference = createResolvedNamedReference(
             functionCall.calleeReference,
             name,
@@ -91,6 +100,8 @@ class FirCallResolver(
             result.candidates,
             result.applicability,
             functionCall.explicitReceiver,
+            expectedCallKind = if (forceCandidates != null) CallKind.VariableAccess else null,
+            expectedCandidates = forceCandidates
         )
 
         val resultExpression = functionCall.transformCalleeReference(StoreNameReference, nameReference)
@@ -147,7 +158,7 @@ class FirCallResolver(
 
         val info = CallInfo(
             qualifiedAccess,
-            if (qualifiedAccess is FirFunctionCall || forceCallKind == CallKind.Function) CallKind.Function else CallKind.VariableAccess,
+            forceCallKind ?: if (qualifiedAccess is FirFunctionCall) CallKind.Function else CallKind.VariableAccess,
             name,
             explicitReceiver,
             argumentList,
@@ -229,7 +240,7 @@ class FirCallResolver(
             reducedCandidates,
             result.applicability,
             qualifiedAccess.explicitReceiver,
-            functionCallExpected = functionCallExpected
+            expectedCallKind = if (functionCallExpected) CallKind.Function else null
         )
 
         val referencedSymbol = when (nameReference) {
@@ -576,38 +587,66 @@ class FirCallResolver(
         applicability: CandidateApplicability,
         explicitReceiver: FirExpression? = null,
         createResolvedReferenceWithoutCandidateForLocalVariables: Boolean = true,
-        functionCallExpected: Boolean = false
+        expectedCallKind: CallKind? = null,
+        expectedCandidates: Collection<Candidate>? = null
     ): FirNamedReference {
         val source = reference.source
         return when {
-            functionCallExpected -> {
+            expectedCallKind != null -> {
                 fun isValueParametersNotEmpty(candidate: Candidate): Boolean {
                     return (candidate.symbol.fir as? FirFunction)?.valueParameters?.size?.let { it > 0 } ?: false
                 }
 
                 val candidate = candidates.singleOrNull()
+
+                val diagnostic = if (expectedCallKind == CallKind.Function) {
+                    ConeFunctionCallExpectedError(
+                        name,
+                        candidate?.let { isValueParametersNotEmpty(it) } ?: candidates.any { isValueParametersNotEmpty(it) })
+                } else {
+                    val singleExpectedCandidate = expectedCandidates?.singleOrNull()
+                    if (singleExpectedCandidate?.symbol?.fir is FirRegularClass) {
+                        ConeUnresolvedNameError(name)
+                        // TODO: ConeResolutionToClassifierError()
+                    } else {
+                        val coneType = explicitReceiver?.typeRef?.coneType
+                        if (coneType != null && !coneType.isUnit) {
+                            ConeFunctionExpectedError(
+                                name.asString(),
+                                (singleExpectedCandidate?.symbol?.fir as? FirTypedDeclaration)?.returnTypeRef?.coneType ?: coneType
+                            )
+                        } else {
+                            ConeUnresolvedNameError(name)
+                        }
+                    }
+                }
+
                 if (candidate != null) {
                     createErrorReferenceWithExistingCandidate(
                         candidate,
-                        ConeFunctionCallExpectedError(name, isValueParametersNotEmpty(candidate)),
+                        diagnostic,
                         source,
                         transformer.resolutionContext,
                         components.resolutionStageRunner
                     )
                 } else {
-                    buildErrorReference(
-                        callInfo,
-                        ConeFunctionCallExpectedError(name, candidates.any { isValueParametersNotEmpty(it) }),
-                        source
-                    )
+                    buildErrorReference(callInfo, diagnostic, source)
                 }
             }
 
-            candidates.isEmpty() -> buildErrorReference(
-                callInfo,
-                ConeUnresolvedNameError(name),
-                source
-            )
+            candidates.isEmpty() -> {
+                val diagnostic = if (name.asString() == "invoke" && explicitReceiver is FirConstExpression<*>) {
+                    ConeFunctionExpectedError(explicitReceiver.value?.toString() ?: "", explicitReceiver.typeRef.coneType)
+                } else {
+                    ConeUnresolvedNameError(name)
+                }
+
+                buildErrorReference(
+                    callInfo,
+                    diagnostic,
+                    source
+                )
+            }
 
             candidates.size > 1 -> buildErrorReference(
                 callInfo,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/diagnostics/FirDiagnostics.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.diagnostics.ConeDiagnostic
+import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.resolve.calls.Candidate
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
@@ -49,6 +50,10 @@ class ConeFunctionCallExpectedError(val name: Name, val hasValueParameters: Bool
     override val reason: String get() = "Function call expected: $name(${if (hasValueParameters) "..." else ""})"
 }
 
+class ConeFunctionExpectedError(val expression: String, val type: ConeKotlinType) : ConeDiagnostic() {
+    override val reason: String get() = "Expression '$expression' of type '$type' cannot be invoked as a function"
+}
+
 class ConeHiddenCandidateError(
     val candidateSymbol: FirBasedSymbol<*>
 ) : ConeDiagnostic() {

compiler/testData/diagnostics/tests/FunctionCalleeExpressions.fir.kt

@@ -50,25 +50,25 @@ fun main(args : Array<String>) {
     checkSubtype<Int>(b)
     <!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>fooT2<!>()(1) // : Any?
 
-    <!UNRESOLVED_REFERENCE!>1<!>()
-    <!UNRESOLVED_REFERENCE!>1<!>{}
-    <!UNRESOLVED_REFERENCE!>1<!>(){}
+    <!FUNCTION_EXPECTED!>1<!>()
+    <!FUNCTION_EXPECTED!>1<!>{}
+    <!FUNCTION_EXPECTED!>1<!>(){}
 }
 
 fun f() :  Int.() -> Unit = {}
 
 fun main1() {
-    1.(<!UNRESOLVED_REFERENCE!>fun Int.() = 1<!>)();
+    1.(<!FUNCTION_EXPECTED!>fun Int.() = 1<!>)();
     {1}();
     (fun (x : Int) = x)(1)
-    1.(<!UNRESOLVED_REFERENCE!>fun Int.(x : Int) = x<!>)(1);
+    1.(<!FUNCTION_EXPECTED!>fun Int.(x : Int) = x<!>)(1);
     l@{1}()
-    1.((<!UNRESOLVED_REFERENCE!>fun Int.() = 1<!>))()
-    1.(<!UNRESOLVED_REFERENCE!>f()<!>)()
-    1.<!UNRESOLVED_REFERENCE!>if(true){f()}else{f()}<!>()
-    1.<!UNRESOLVED_REFERENCE!>if(true)(fun Int.() {})else{f()}<!>()
+    1.((<!FUNCTION_EXPECTED!>fun Int.() = 1<!>))()
+    1.(<!FUNCTION_EXPECTED!>f()<!>)()
+    1.<!FUNCTION_EXPECTED!>if(true){f()}else{f()}<!>()
+    1.<!FUNCTION_EXPECTED!>if(true)(fun Int.() {})else{f()}<!>()
 
-    1.<!UNRESOLVED_REFERENCE!>"sdf"<!>()
+    1.<!FUNCTION_EXPECTED!>"sdf"<!>()
 
     1.<!ILLEGAL_SELECTOR!>"sdf"<!>
     1.<!ILLEGAL_SELECTOR!>{}<!>
@@ -78,7 +78,7 @@ fun main1() {
 fun test() {
     {x : Int -> 1}(<!NO_VALUE_FOR_PARAMETER!>)<!>;
     (fun Int.() = 1)(<!NO_VALUE_FOR_PARAMETER!>)<!>
-    "sd".(<!UNRESOLVED_REFERENCE!>fun Int.() = 1<!>)()
+    "sd".(<!FUNCTION_EXPECTED!>fun Int.() = 1<!>)()
     val i : Int? = null
     i.(<!UNRESOLVED_REFERENCE!>fun Int.() = 1<!>)();
     <!INAPPLICABLE_CANDIDATE!>{}<!><Int>()

compiler/testData/diagnostics/tests/extensions/kt1875.fir.kt

@@ -14,7 +14,7 @@ fun test(t: T) {
 }
 
 fun test1(t: T?) {
-    t.<!UNRESOLVED_REFERENCE!>f<!>(1) // todo resolve f as value and report UNSAFE_CALL
+    t.<!FUNCTION_EXPECTED!>f<!>(1) // todo resolve f as value and report UNSAFE_CALL
     t?.<!UNSAFE_IMPLICIT_INVOKE_CALL!>f<!>(1)
     t<!UNSAFE_CALL!>.<!>f?.invoke(1)
     t?.f?.invoke(1)

compiler/testData/diagnostics/tests/extensions/throwOutCandidatesByReceiver.fir.kt

@@ -34,7 +34,7 @@ fun test4() {
 // should be an error on receiver, shouldn't be thrown away
 
 fun test5() {
-    1.(<!UNRESOLVED_REFERENCE!>fun String.()=1<!>)()
+    1.(<!FUNCTION_EXPECTED!>fun String.()=1<!>)()
 }
 
 fun <R: Any> R?.sure() : R = this!!

compiler/testData/diagnostics/tests/incompleteCode/kt2014.fir.kt

@@ -12,7 +12,7 @@ fun x(f : Foo) {
     f.<!FUNCTION_CALL_EXPECTED!>prop<!>
     f.<!FUNCTION_CALL_EXPECTED!>bar<!>
 
-    f.<!UNRESOLVED_REFERENCE!>a<!>()
+    f.<!FUNCTION_EXPECTED!>a<!>()
     <!UNRESOLVED_REFERENCE!>c<!>()
     <!INVISIBLE_REFERENCE!>R<!>()
 }

compiler/testData/diagnostics/tests/inner/innerConstructorsFromQualifiers.fir.kt

@@ -33,4 +33,4 @@ fun bar() {
         Inner()
         Inner(1)
     }
-}
+}

compiler/testData/diagnostics/tests/kt310.fir.kt

@@ -1,4 +0,0 @@
-
-fun f(c: LongRange): Int {
-    return c.<!UNRESOLVED_REFERENCE!>start<!>()
-}

compiler/testData/diagnostics/tests/kt310.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 
 fun f(c: LongRange): Int {
     return c.<!FUNCTION_EXPECTED!>start<!>()

compiler/testData/diagnostics/tests/resolve/invoke/errors/unresolvedInvoke.fir.kt

@@ -1,5 +1,5 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION
 fun foo(i: Int) {
     <!UNRESOLVED_REFERENCE!>i<!>()
-    <!UNRESOLVED_REFERENCE!>1<!>()
-}
+    <!FUNCTION_EXPECTED!>1<!>()
+}

compiler/testData/diagnostics/tests/resolve/invoke/errors/wrongReceiverForInvokeOnExpression.fir.kt

@@ -1,7 +1,7 @@
 
 fun test1() {
-    1. (<!UNRESOLVED_REFERENCE!>fun String.(i: Int) = i<!> )(1)
-    1.(<!UNRESOLVED_REFERENCE!>label@ fun String.(i: Int) = i<!> )(1)
+    1. (<!FUNCTION_EXPECTED!>fun String.(i: Int) = i<!> )(1)
+    1.(<!FUNCTION_EXPECTED!>label@ fun String.(i: Int) = i<!> )(1)
 }
 
 fun test2(f: String.(Int) -> Unit) {
@@ -12,5 +12,5 @@ fun test2(f: String.(Int) -> Unit) {
 fun test3() {
     fun foo(): String.(Int) -> Unit = {}
 
-    1.(<!UNRESOLVED_REFERENCE!>foo()<!>)(1)
+    1.(<!FUNCTION_EXPECTED!>foo()<!>)(1)
 }

compiler/testData/diagnostics/tests/resolve/invoke/invokeAndSmartCast.fir.kt

@@ -2,11 +2,11 @@ class A(val x: (String.() -> Unit)?)
 
 fun test(a: A) {
     if (a.x != null) {
-        "".(<!UNRESOLVED_REFERENCE!>a.x<!>)()
+        "".(<!FUNCTION_EXPECTED!>a.x<!>)()
         a.x("") // todo
         (a.x)("")
     }
-    "".(<!UNRESOLVED_REFERENCE!>a.x<!>)()
+    "".(<!FUNCTION_EXPECTED!>a.x<!>)()
     a.<!UNSAFE_IMPLICIT_INVOKE_CALL!>x<!>("")
     <!UNSAFE_IMPLICIT_INVOKE_CALL!>(a.x)<!>("")
 

compiler/testData/diagnostics/tests/resolve/invoke/kt30695_2.fir.kt

@@ -26,7 +26,7 @@ val Cls.extensionProperty: MemberInvokeOwner
 
 fun testNullableReceiver(nullable: Cls?) {
     nullable?.extensionProperty()
-    nullable.<!UNRESOLVED_REFERENCE!>extensionProperty<!>()
+    nullable.<!FUNCTION_EXPECTED!>extensionProperty<!>()
 }
 
 fun testNotNullableReceiver(notNullable: Cls) {

compiler/testData/diagnostics/tests/secondaryConstructors/headerCallChecker/operatorCall.fir.kt

@@ -5,7 +5,7 @@ class D : C {
             {
                 val s = ""
                 <!UNRESOLVED_REFERENCE!>s<!>()
-                <!UNRESOLVED_REFERENCE!>""<!>()
+                <!FUNCTION_EXPECTED!>""<!>()
                 42
             }())
 

compiler/testData/diagnostics/tests/smartCasts/variables/ifElseBlockInsideDoWhileWithBreak.fir.kt

@@ -12,5 +12,5 @@ public fun foo(xx: Any): Int {
         y.length
     } while (true)
     // We could have smart cast here but with break it's hard to detect
-    return x.<!UNRESOLVED_REFERENCE!>length<!>()
-}
+    return x.<!FUNCTION_EXPECTED!>length<!>()
+}

compiler/testData/diagnostics/tests/smartCasts/variables/whileTrue.fir.kt

@@ -0,0 +1,13 @@
+fun x(): Boolean { return true }
+
+public fun foo(pp: Any): Int {
+    var p = pp
+    while(true) {
+        (p as String).length
+        if (x()) break
+        p = 42
+    }
+    // Smart cast is NOT possible here
+    // (we could provide it but p = 42 makes it difficult to understand)
+    return p.<!FUNCTION_EXPECTED!>length<!>()
+}

compiler/testData/diagnostics/tests/smartCasts/variables/whileTrue.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 fun x(): Boolean { return true }
 
 public fun foo(pp: Any): Int {
@@ -11,4 +10,4 @@ public fun foo(pp: Any): Int {
     // Smart cast is NOT possible here
     // (we could provide it but p = 42 makes it difficult to understand)
     return p.<!UNRESOLVED_REFERENCE!>length<!>()
-}
+}

compiler/tests-spec/testData/diagnostics/notLinked/overload-resolution/building-the-overload-candidate-set-ocs/infix-function-call/pos/2.fir.kt

@@ -8,9 +8,9 @@ class C() {
 // TESTCASE NUMBER: 1
 fun case1() {
     val b: B = B(C())
-    b <!UNRESOLVED_REFERENCE!>memberVal<!> 1           //nok UNRESOLVED_REFERENCE
+    b <!FUNCTION_EXPECTED!>memberVal<!> 1           //nok UNRESOLVED_REFERENCE
     b.memberVal.<!UNRESOLVED_REFERENCE!>invoke<!>(2)   //nok UNRESOLVED_REFERENCE
-    b.<!UNRESOLVED_REFERENCE!>memberVal<!>(1)          //nok FUNCTION_EXPECTED
+    b.<!FUNCTION_EXPECTED!>memberVal<!>(1)          //nok FUNCTION_EXPECTED
 
     if (b.memberVal is C) {
 

compiler/tests-spec/testData/diagnostics/notLinked/overload-resolution/building-the-overload-candidate-set-ocs/infix-function-call/pos/3.fir.kt

@@ -9,9 +9,9 @@ class C() {
 // TESTCASE NUMBER: 1
 fun case1() {
     val b: B = B(C())
-    b <!UNRESOLVED_REFERENCE!>memberVal<!> 1           //nok UNRESOLVED_REFERENCE
+    b <!FUNCTION_EXPECTED!>memberVal<!> 1           //nok UNRESOLVED_REFERENCE
     b.memberVal.<!UNRESOLVED_REFERENCE!>invoke<!>(2)   //nok UNRESOLVED_REFERENCE
-    b.<!UNRESOLVED_REFERENCE!>memberVal<!>(1)          //nok FUNCTION_EXPECTED
+    b.<!FUNCTION_EXPECTED!>memberVal<!>(1)          //nok FUNCTION_EXPECTED
 
     b.memberVal as C
 

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -327,6 +327,14 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.FUNCTION_EXPECTED) { firDiagnostic ->
+        FunctionExpectedImpl(
+            firDiagnostic.a,
+            firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.b),
+            firDiagnostic as FirPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.SUPER_IS_NOT_AN_EXPRESSION) { firDiagnostic ->
         SuperIsNotAnExpressionImpl(
             firDiagnostic as FirPsiDiagnostic,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -257,6 +257,12 @@ sealed class KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = NoReceiverAllowed::class
     }
 
+    abstract class FunctionExpected : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = FunctionExpected::class
+        abstract val expression: String
+        abstract val type: KtType
+    }
+
     abstract class SuperIsNotAnExpression : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = SuperIsNotAnExpression::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -381,6 +381,15 @@ internal class NoReceiverAllowedImpl(
     override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
 }
 
+internal class FunctionExpectedImpl(
+    override val expression: String,
+    override val type: KtType,
+    firDiagnostic: FirPsiDiagnostic,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.FunctionExpected(), KtAbstractFirDiagnostic<PsiElement> {
+    override val firDiagnostic: FirPsiDiagnostic by weakRef(firDiagnostic)
+}
+
 internal class SuperIsNotAnExpressionImpl(
     firDiagnostic: FirPsiDiagnostic,
     override val token: ValidityToken,