[NI] Fix reporting smartcast diagnostics for intersection types

#KT-30826 Fixed

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

@@ -19529,6 +19529,11 @@ public class FirDiagnosticsSmokeTestGenerated extends AbstractFirDiagnosticsSmok
             runTest("compiler/testData/diagnostics/tests/smartCasts/kt2865.kt");
         }
 
+        @TestMetadata("kt30826.kt")
+        public void testKt30826() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/smartCasts/kt30826.kt");
+        }
+
         @TestMetadata("kt3224.kt")
         public void testKt3224() throws Exception {
             runTest("compiler/testData/diagnostics/tests/smartCasts/kt3224.kt");

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/SmartCastManager.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.resolve.calls.smartcasts
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
 import org.jetbrains.kotlin.diagnostics.Errors
@@ -33,6 +34,7 @@ import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitReceiver
 import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
+import org.jetbrains.kotlin.types.typeUtil.expandIntersectionTypeIfNecessary
 import java.util.*
 
 class SmartCastManager {
@@ -178,8 +180,13 @@ class SmartCastManager {
             recordExpressionType: Boolean
         ): SmartCastResult? {
             val calleeExpression = call?.calleeExpression
+            val expectedTypes = if (c.languageVersionSettings.supportsFeature(LanguageFeature.NewInference))
+                expectedType.expandIntersectionTypeIfNecessary()
+            else
+                listOf(expectedType)
+
             for (possibleType in c.dataFlowInfo.getCollectedTypes(dataFlowValue, c.languageVersionSettings)) {
-                if (ArgumentTypeResolver.isSubtypeOfForArgumentType(possibleType, expectedType) &&
+                if (expectedTypes.any { ArgumentTypeResolver.isSubtypeOfForArgumentType(possibleType, it) } &&
                     (additionalPredicate == null || additionalPredicate(possibleType))
                 ) {
                     if (expression != null) {

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/AdditionalDiagnosticReporter.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.descriptors.ReceiverParameterDescriptor
 import org.jetbrains.kotlin.resolve.calls.model.*
 import org.jetbrains.kotlin.types.UnwrappedType
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
+import org.jetbrains.kotlin.types.typeUtil.expandIntersectionTypeIfNecessary
 
 // very initial state of component
 // todo: handle all diagnostic inside DiagnosticReporterByTrackingStrategy
@@ -43,10 +44,14 @@ class AdditionalDiagnosticReporter(private val languageVersionSettings: Language
         expectedResultType: UnwrappedType
     ): SmartCastDiagnostic? {
         if (argument !is ExpressionKotlinCallArgument) return null
-        if (!KotlinTypeChecker.DEFAULT.isSubtypeOf(argument.receiver.receiverValue.type, expectedResultType)) {
+
-            return SmartCastDiagnostic(argument, expectedResultType.unwrap(), candidate.atom)
+        val types = expectedResultType.expandIntersectionTypeIfNecessary()
-        }
+
-        return null
+        val argumentType = argument.receiver.receiverValue.type
+        val isSubtype = types.map { KotlinTypeChecker.DEFAULT.isSubtypeOf(argumentType, it) }
+        if (isSubtype.any { it }) return null
+
+        return SmartCastDiagnostic(argument, types.first().unwrap(), candidate.atom)
     }
 
     private fun reportSmartCastOnReceiver(

compiler/testData/diagnostics/tests/generics/nullability/smartCasts.kt

@@ -30,9 +30,9 @@ fun <T : CharSequence?> foo(x: T) {
         <!DEBUG_INFO_SMARTCAST!>x<!>.length
         x<!UNNECESSARY_SAFE_CALL!>?.<!>length
 
-        x.bar1()
+        <!NI;DEBUG_INFO_SMARTCAST!>x<!>.bar1()
         x.bar2()
-        <!OI;DEBUG_INFO_SMARTCAST!>x<!>.bar3()
+        <!DEBUG_INFO_SMARTCAST!>x<!>.bar3()
     }
 
     if (x is CharSequence) {

compiler/testData/diagnostics/tests/generics/nullability/smartCastsValueArgument.kt

@@ -24,7 +24,7 @@ fun <T : CharSequence?> foo(x: T) {
         y1 = <!DEBUG_INFO_SMARTCAST!>x<!>
         y2 = <!DEBUG_INFO_SMARTCAST!>x<!>
 
-        bar1(<!OI;DEBUG_INFO_SMARTCAST!>x<!>)
+        bar1(<!DEBUG_INFO_SMARTCAST!>x<!>)
         bar2(<!DEBUG_INFO_SMARTCAST!>x<!>)
         bar3(<!DEBUG_INFO_SMARTCAST!>x<!>)
     }

compiler/testData/diagnostics/tests/smartCasts/intersectionScope/unstableSmartCast.kt

@@ -31,8 +31,8 @@ fun test() {
         x.foo().checkType { _<CharSequence?>() }
         x.baz("")
         x.baz(1).checkType { _<Unit>() }
-        <!OI;SMARTCAST_IMPOSSIBLE!>x<!>.baz(1, 2)
+        <!SMARTCAST_IMPOSSIBLE!>x<!>.baz(1, 2)
 
-        <!OI;SMARTCAST_IMPOSSIBLE!>x<!>.foobar().checkType { _<String>() }
+        <!SMARTCAST_IMPOSSIBLE!>x<!>.foobar().checkType { _<String>() }
     }
 }

compiler/testData/diagnostics/tests/smartCasts/kt30826.kt

@@ -0,0 +1,19 @@
+// !WITH_NEW_INFERENCE
+// Issue: KT-30826
+
+interface I1
+interface I2 {
+    fun foo() {}
+}
+
+class A : I1, I2
+
+fun foo(x: I1?) {
+    var y = x
+    y as I2
+    val bar = {
+        <!SMARTCAST_IMPOSSIBLE!>y<!>.foo() // NPE in NI, smartcast impossible in OI
+    }
+    y = null
+    bar()
+}

compiler/testData/diagnostics/tests/smartCasts/kt30826.txt

@@ -0,0 +1,24 @@
+package
+
+public fun foo(/*0*/ x: I1?): kotlin.Unit
+
+public final class A : I1, I2 {
+    public constructor A()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface I1 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface I2 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests-spec/testData/diagnostics/linked/type-inference/smart-casts/smart-casts-sources/p-4/pos/1.12.kt

@@ -61,7 +61,7 @@ fun <T> T?.case_5() {
 
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>equals<!>(this)
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>itest1<!>()
-            apply {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>apply<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
@@ -69,7 +69,7 @@ fun <T> T?.case_5() {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(this)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest1()
             }
-            also {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>also<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest1()
@@ -89,14 +89,14 @@ fun <T> T?.case_6() {
 
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>equals<!>(this)
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>itest1<!>()
-            apply {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>apply<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
                 itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(this)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest1()
             }
-            also {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>also<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.equals(it)
@@ -114,14 +114,14 @@ fun <T> T.case_7() {
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T"), DEBUG_INFO_SMARTCAST!>x<!>.equals(this)
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T"), DEBUG_INFO_SMARTCAST!>x<!>.itest1()
 
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>
                 equals(this)
                 itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.equals(this)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.itest1()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.equals(it)
@@ -140,14 +140,14 @@ fun <T> T.case_8() {
 
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>equals<!>(this)
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>itest1<!>()
-            apply {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>apply<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>
                 equals(this)
                 itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.equals(this)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.itest1()
             }
-            also {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>also<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.equals(it)
@@ -214,14 +214,14 @@ fun <T : Number> T?.case_11() {
 
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>equals<!>(this)
             <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>itest1<!>()
-            apply {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>apply<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
                 itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(this)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest1()
             }
-            also {
+            <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>also<!> {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.equals(it)
@@ -1706,11 +1706,11 @@ fun <T> T.case_65() {
             if (this != null) {
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & Interface2 & T & T!!"), DEBUG_INFO_EXPRESSION_TYPE("T")!>this<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface1"), DEBUG_INFO_EXPRESSION_TYPE("T"), DEBUG_INFO_SMARTCAST!>this<!>.equals(<!UNRESOLVED_REFERENCE!>x<!>)
-                apply {
+                <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>apply<!> {
                     <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}")!>this<!>
                     <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}")!>this<!>.equals(this)
                 }
-                also {
+                <!DEBUG_INFO_IMPLICIT_RECEIVER_SMARTCAST!>also<!> {
                     <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}")!>it<!>
                     <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & Interface2 & T!!}")!>it<!>.equals(it)
                 }

compiler/tests-spec/testData/diagnostics/linked/type-inference/smart-casts/smart-casts-sources/p-4/pos/1.13.kt

@@ -65,7 +65,7 @@ fun <T> case_5(x: T?) {
 
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T?"), DEBUG_INFO_SMARTCAST!>x<!>.equals(x)
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T?"), DEBUG_INFO_SMARTCAST!>x<!>.itest()
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
@@ -73,7 +73,7 @@ fun <T> case_5(x: T?) {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(x)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest()
@@ -93,14 +93,14 @@ fun <T> case_6(x: T?) {
 
             <!DEBUG_INFO_SMARTCAST!>x<!>.equals(x)
             <!DEBUG_INFO_SMARTCAST!>x<!>.itest()
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
                 itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(x)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.equals(it)
@@ -118,14 +118,14 @@ fun <T> case_7(y: T) {
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T"), DEBUG_INFO_SMARTCAST!>x<!>.equals(x)
             <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & T"), DEBUG_INFO_SMARTCAST!>x<!>.itest()
 
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>
                 equals(this)
                 itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.equals(x)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.itest()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.equals(it)
@@ -144,14 +144,14 @@ fun <T> case_8(x: T) {
 
             <!DEBUG_INFO_SMARTCAST!>x<!>.equals(x)
             <!DEBUG_INFO_SMARTCAST!>x<!>.itest()
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>
                 equals(this)
                 itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.equals(x)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>this<!>.itest()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T!!}")!>it<!>.equals(it)
@@ -218,14 +218,14 @@ fun <T : Number> case_11(x: T?) {
 
             <!DEBUG_INFO_SMARTCAST!>x<!>.equals(x)
             <!DEBUG_INFO_SMARTCAST!>x<!>.itest()
-            x.apply {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.apply {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>
                 equals(this)
                 itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.equals(x)
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}"), DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>this<!>.itest()
             }
-            x.also {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.also {
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.itest()
                 <!DEBUG_INFO_EXPRESSION_TYPE("{Interface1 & T?!!}")!>it<!>.equals(it)

compiler/tests-spec/testData/diagnostics/linked/type-inference/smart-casts/smart-casts-sources/p-4/pos/1.5.kt

@@ -188,7 +188,7 @@ fun case_11(x: Any?) {
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.itest1()
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.itest2()
 
-                <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & Interface2 & kotlin.Any & kotlin.Any?")!>x<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
+                <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
             }
         }
     }
@@ -206,7 +206,7 @@ fun case_12(x: Any?) {
         <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.itest1()
         <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.itest2()
 
-        <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & Interface2 & kotlin.Any & kotlin.Any?")!>x<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
+        <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>x<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
     }
 }
 

compiler/tests-spec/testData/diagnostics/linked/type-inference/smart-casts/smart-casts-sources/p-4/pos/1.6.kt

@@ -903,7 +903,7 @@ fun case_71(t: Any?) {
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.itest2()
                 <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.itest()
 
-                <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & Interface2 & kotlin.Any & kotlin.Any?")!>t<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
+                <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
             }
         }
     }
@@ -924,7 +924,7 @@ fun case_72(t: Any?, z1: Nothing?) {
         <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.itest2()
         <!DEBUG_INFO_EXPRESSION_TYPE("Interface2 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.itest()
 
-        <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & Interface2 & kotlin.Any & kotlin.Any?")!>t<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
+        <!DEBUG_INFO_EXPRESSION_TYPE("Interface1 & kotlin.Any?"), DEBUG_INFO_SMARTCAST!>t<!>.let { <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest1(); <!DEBUG_INFO_EXPRESSION_TYPE("{Any & Interface1 & Interface2}")!>it<!>.itest2() }
     }
 }
 

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -19606,6 +19606,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/kt2865.kt");
             }
 
+            @TestMetadata("kt30826.kt")
+            public void testKt30826() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/kt30826.kt");
+            }
+
             @TestMetadata("kt3224.kt")
             public void testKt3224() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/kt3224.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -19531,6 +19531,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/smartCasts/kt2865.kt");
             }
 
+            @TestMetadata("kt30826.kt")
+            public void testKt30826() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/kt30826.kt");
+            }
+
             @TestMetadata("kt3224.kt")
             public void testKt3224() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/kt3224.kt");

core/descriptors/src/org/jetbrains/kotlin/types/TypeUtils.kt

@@ -243,3 +243,12 @@ val TypeParameterDescriptor.representativeUpperBound: KotlinType
         } ?: upperBounds.first()
     }
 
+fun KotlinType.expandIntersectionTypeIfNecessary(): Collection<KotlinType> {
+    if (constructor !is IntersectionTypeConstructor) return listOf(this)
+    val types = constructor.supertypes
+    return if (isMarkedNullable) {
+        types.map { it.makeNullable() }
+    } else {
+        types
+    }
+}