[FIR] Preserve enhanced mutability when nullability was enhanced for warning

#KT-56989

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendForeignAnnotationsCompiledJavaTestGenerated.java

@@ -1189,6 +1189,12 @@ public class FirPsiOldFrontendForeignAnnotationsCompiledJavaTestGenerated extend
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendForeignAnnotationsCompiledJavaWithPsiClassReadingTestGenerated.java

@@ -1247,6 +1247,12 @@ public class FirPsiOldFrontendForeignAnnotationsCompiledJavaWithPsiClassReadingT
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendForeignAnnotationsSourceJavaTestGenerated.java

@@ -1247,6 +1247,12 @@ public class FirPsiOldFrontendForeignAnnotationsSourceJavaTestGenerated extends
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/checkers/expression/FirExpressionJavaNullabilityWarningCheckers.kt

@@ -151,7 +151,10 @@ internal fun FirExpression.checkExpressionForEnhancedTypeMismatch(
     val (actualTypeForComparison, expectedTypeForComparison) = getEnhancedTypesForComparison(actualType, expectedType, context)
         ?: return
 
-    if (!actualTypeForComparison.isSubtypeOf(context.session.typeContext, expectedTypeForComparison)) {
+    if (!actualTypeForComparison.isSubtypeOf(context.session.typeContext, expectedTypeForComparison) &&
+        // Don't report anything if the original types didn't match.
+        actualType.isSubtypeOf(context.session.typeContext, expectedType.asExpectedFunctionTypeIfSam(actualType, context))
+    ) {
         reporter.reportOn(source, factory, actualTypeForComparison, expectedTypeForComparison, context)
     }
 }
@@ -175,16 +178,22 @@ private fun getEnhancedTypesForComparison(
     val actualTypeForComparison = enhancedActualType ?: actualType
     val expectedTypeForComparison = enhancedExpectedType ?: expectedType
 
-    val expectedTypeAsFunctionTypeIfSam = if (
+    val expectedTypeAsFunctionTypeIfSam = expectedTypeForComparison.asExpectedFunctionTypeIfSam(actualTypeForComparison, context)
-        actualTypeForComparison.isSomeFunctionType(context.session) &&
-        !expectedTypeForComparison.isSomeFunctionType(context.session)
-    ) {
-        // TODO remove after KT-62847
-        val samResolver = FirSamResolver(context.session, context.scopeSession)
-        samResolver.getFunctionTypeForPossibleSamType(expectedTypeForComparison) ?: expectedTypeForComparison
-    } else {
-        expectedTypeForComparison
-    }
 
     return actualTypeForComparison to expectedTypeAsFunctionTypeIfSam
 }
+
+/**
+ * If the receiver is a SAM type and the [actualType] is a function type, converts the receiver to the corresponding function type.
+ * Otherwise, returns receiver.
+ *
+ * TODO remove after KT-62847
+ * */
+private fun ConeKotlinType.asExpectedFunctionTypeIfSam(actualType: ConeKotlinType, context: CheckerContext): ConeKotlinType {
+    if (!actualType.isSomeFunctionType(context.session) || isSomeFunctionType(context.session)) {
+        return this
+    }
+
+    val samResolver = FirSamResolver(context.session, context.scopeSession)
+    return samResolver.getFunctionTypeForPossibleSamType(this) ?: this
+}

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/javaTypeUtils.kt

@@ -106,7 +106,14 @@ private fun ConeSimpleKotlinType.enhanceInflexibleType(
     )
 
     return if (effectiveQualifiers.isNullabilityQualifierForWarning && enhanced != null) {
-        this.withAttributes(attributes.plus(EnhancedTypeForWarningAttribute(enhanced)))
+        val newAttributes = attributes.plus(EnhancedTypeForWarningAttribute(enhanced))
+
+        if (enhancedTag != lookupTag) {
+            // Handle case when mutability was enhanced and nullability was enhanced for warning.
+            enhancedTag.constructType(typeArguments, isNullable, newAttributes)
+        } else {
+            this.withAttributes(newAttributes)
+        }
     } else {
         enhanced
     }

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.fir.kt

@@ -0,0 +1,27 @@
+// NULLABILITY_ANNOTATIONS: @org.jetbrains.annotations:warn
+// DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: ReadOnly.java
+package org.jetbrains.annotations;
+
+public @interface ReadOnly {}
+
+// FILE: J.java
+import java.util.List;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
+
+public class J {
+    @ReadOnly
+    @Nullable
+    public static List<String> foo() {
+        return null;
+    }
+}
+
+// FILE: main.kt
+fun main() {
+    takeMutable(<!ARGUMENT_TYPE_MISMATCH!>J.foo()<!>)
+}
+
+fun takeMutable(l: MutableList<String>) {}

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt

@@ -0,0 +1,27 @@
+// NULLABILITY_ANNOTATIONS: @org.jetbrains.annotations:warn
+// DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: ReadOnly.java
+package org.jetbrains.annotations;
+
+public @interface ReadOnly {}
+
+// FILE: J.java
+import java.util.List;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
+
+public class J {
+    @ReadOnly
+    @Nullable
+    public static List<String> foo() {
+        return null;
+    }
+}
+
+// FILE: main.kt
+fun main() {
+    takeMutable(<!NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS!>J.foo()<!>)
+}
+
+fun takeMutable(l: MutableList<String>) {}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/ForeignAnnotationsCompiledJavaTestGenerated.java

@@ -1189,6 +1189,12 @@ public class ForeignAnnotationsCompiledJavaTestGenerated extends AbstractForeign
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/ForeignAnnotationsCompiledJavaWithPsiClassReadingTestGenerated.java

@@ -1247,6 +1247,12 @@ public class ForeignAnnotationsCompiledJavaWithPsiClassReadingTestGenerated exte
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/ForeignAnnotationsSourceJavaTestGenerated.java

@@ -1247,6 +1247,12 @@ public class ForeignAnnotationsSourceJavaTestGenerated extends AbstractForeignAn
                 runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/methodWithTypeParameter.kt");
             }
 
+            @Test
+            @TestMetadata("mutabilityAndNullabilityForWarning.kt")
+            public void testMutabilityAndNullabilityForWarning() throws Exception {
+                runTest("compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/misc/mutabilityAndNullabilityForWarning.kt");
+            }
+
             @Test
             @TestMetadata("notNullVarargsOverrides.kt")
             public void testNotNullVarargsOverrides() throws Exception {