Do not report redundant else for enum / sealed from another module

Related to KT-17497

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -54,6 +54,7 @@ import org.jetbrains.kotlin.resolve.calls.resolvedCallUtil.hasThisOrNoDispatchRe
 import org.jetbrains.kotlin.resolve.calls.util.FakeCallableDescriptorForObject
 import org.jetbrains.kotlin.resolve.calls.util.isSingleUnderscore
 import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils.*
 import org.jetbrains.kotlin.types.expressions.ExpressionTypingUtils
@@ -797,7 +798,14 @@ class ControlFlowInformationProvider private constructor(
                     val subjectType = trace.getType(subjectExpression)
                     if (elseEntry != null) {
                         if (missingCases.isEmpty() && subjectType != null && !subjectType.isFlexible()) {
-                            trace.report(REDUNDANT_ELSE_IN_WHEN.on(elseEntry))
+                            val subjectClass = subjectType.constructor.declarationDescriptor as? ClassDescriptor
+                            val pseudocodeElement = instruction.owner.correspondingElement
+                            val pseudocodeDescriptor = trace[DECLARATION_TO_DESCRIPTOR, pseudocodeElement]
+                            if (subjectClass == null ||
+                                KotlinBuiltIns.isBooleanOrNullableBoolean(subjectType) ||
+                                subjectClass.module == pseudocodeDescriptor?.module) {
+                                trace.report(REDUNDANT_ELSE_IN_WHEN.on(elseEntry))
+                            }
                         }
                         continue
                     }

compiler/testData/diagnostics/tests/multimodule/redundantElseInWhen.kt

@@ -0,0 +1,45 @@
+// MODULE: m1
+// FILE: a.kt
+
+package test
+
+enum class E {
+    FIRST
+}
+
+sealed class S
+
+class Derived : S()
+
+// MODULE: m2(m1)
+// FILE: b.kt
+
+package other
+
+import test.*
+
+fun foo(e: E) = when (e) {
+    E.FIRST -> 42
+    else -> -42
+}
+
+fun bar(s: S?) = when (s) {
+    is Derived -> "Derived"
+    null -> ""
+    else -> TODO("What?!?!")
+}
+
+fun baz(b: Boolean?) = when (b) {
+    true -> 1
+    false -> 0
+    null -> -1
+    // Still warning
+    <!REDUNDANT_ELSE_IN_WHEN!>else<!> -> TODO()
+}
+
+fun baz(b: Boolean) = when (b) {
+    true -> 1
+    false -> 0
+    // Still warning
+    <!REDUNDANT_ELSE_IN_WHEN!>else<!> -> TODO()
+}

compiler/testData/diagnostics/tests/multimodule/redundantElseInWhen.txt

@@ -0,0 +1,52 @@
+// -- Module: <m1> --
+package
+
+package test {
+
+    public final class Derived : test.S {
+        public constructor Derived()
+        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 final enum class E : kotlin.Enum<test.E> {
+        enum entry FIRST
+
+        private constructor E()
+        public final override /*1*/ /*fake_override*/ val name: kotlin.String
+        public final override /*1*/ /*fake_override*/ val ordinal: kotlin.Int
+        protected final override /*1*/ /*fake_override*/ fun clone(): kotlin.Any
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: test.E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        protected/*protected and package*/ final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun finalize(): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ /*isHiddenForResolutionEverywhereBesideSupercalls*/ fun getDeclaringClass(): java.lang.Class<test.E!>!
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        // Static members
+        public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): test.E
+        public final /*synthesized*/ fun values(): kotlin.Array<test.E>
+    }
+
+    public sealed class S {
+        private constructor S()
+        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
+    }
+}
+
+
+// -- Module: <m2> --
+package
+
+package other {
+    public fun bar(/*0*/ s: test.S?): kotlin.String
+    public fun baz(/*0*/ b: kotlin.Boolean): kotlin.Int
+    public fun baz(/*0*/ b: kotlin.Boolean?): kotlin.Int
+    public fun foo(/*0*/ e: test.E): kotlin.Int
+}
+
+package test {
+}

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

@@ -12955,6 +12955,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("redundantElseInWhen.kt")
+            public void testRedundantElseInWhen() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multimodule/redundantElseInWhen.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("varargConflict.kt")
             public void testVarargConflict() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multimodule/varargConflict.kt");