[FIR] KT-56505 Fix checkVisibilityModifier taking wrong modifier list

- KT-56505 occurred because `source.getChild(KtNodeTypes.MODIFIER_LIST)`
  returns any modifier list in the subtree of the source element, not
  necessarily the modifier list belonging to the checked element.
  `depth = 1` restricts the search to the modifier list belonging to the
  checked element itself.
- For example, given `f1` from KT-56505, `getChild` would return the
  modifier list of `public var foo = 0`. Because it contains a
  visibility modifier, `f1` wasn't marked with
  `NO_EXPLICIT_VISIBILITY_IN_API_MODE`.

^KT-56505 fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -32720,6 +32720,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/interfaces.kt");
             }
 
+            @Test
+            @TestMetadata("kt56505.kt")
+            public void testKt56505() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/kt56505.kt");
+            }
+
             @Test
             @TestMetadata("localFunctions.kt")
             public void testLocalFunctions() throws Exception {

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/RedundantVisibilityModifierCheckerWithExplicitApiMode.kt

@@ -1,6 +1,6 @@
 // EXPLICIT_API_MODE: STRICT
 
-fun f1() {
+<!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>fun f1<!>() {
     class LocalClass {
         public var foo = 0
     }
@@ -71,7 +71,7 @@ public interface I2 {
 
 public var baz2: Int = 0
 
-class J1 {
+<!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>class J1<!> {
     protected val baz: Int = 0
         <!REDUNDANT_VISIBILITY_MODIFIER!>protected<!> get() = field * 2
     <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>var baf<!>: Int = 0
@@ -80,7 +80,7 @@ class J1 {
             field = value
         }
 
-    var buf: Int = 0
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>var buf<!>: Int = 0
         <!GETTER_VISIBILITY_DIFFERS_FROM_PROPERTY_VISIBILITY!>private<!> get() = 42
         protected set(value) {
             field = value

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

@@ -32816,6 +32816,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/interfaces.kt");
             }
 
+            @Test
+            @TestMetadata("kt56505.kt")
+            public void testKt56505() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/kt56505.kt");
+            }
+
             @Test
             @TestMetadata("localFunctions.kt")
             public void testLocalFunctions() throws Exception {

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

@@ -32720,6 +32720,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/interfaces.kt");
             }
 
+            @Test
+            @TestMetadata("kt56505.kt")
+            public void testKt56505() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/kt56505.kt");
+            }
+
             @Test
             @TestMetadata("localFunctions.kt")
             public void testLocalFunctions() throws Exception {

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/syntax/FirExplicitApiDeclarationChecker.kt

@@ -23,7 +23,6 @@ import org.jetbrains.kotlin.fir.declarations.impl.FirPrimaryConstructor
 import org.jetbrains.kotlin.fir.declarations.utils.effectiveVisibility
 import org.jetbrains.kotlin.fir.declarations.utils.isData
 import org.jetbrains.kotlin.fir.declarations.utils.isOverride
-import org.jetbrains.kotlin.fir.declarations.utils.visibility
 import org.jetbrains.kotlin.fir.resolve.transformers.publishedApiEffectiveVisibility
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtDeclaration
@@ -48,8 +47,8 @@ object FirExplicitApiDeclarationChecker : FirDeclarationSyntaxChecker<FirDeclara
         // Enum entries do not have visibilities
         if (element is FirEnumEntry) return
         if (!element.effectiveVisibility.publicApi && element.publishedApiEffectiveVisibility == null) return
-        val lastDeclaration = context.containingDeclarations.lastOrNull()
-        if ((lastDeclaration as? FirMemberDeclaration)?.effectiveVisibility?.publicApi == false) {
+        val lastContainingDeclaration = context.containingDeclarations.lastOrNull()
+        if ((lastContainingDeclaration as? FirMemberDeclaration)?.effectiveVisibility?.publicApi == false) {
             return
         }
 
@@ -64,7 +63,7 @@ object FirExplicitApiDeclarationChecker : FirDeclarationSyntaxChecker<FirDeclara
         context: CheckerContext,
         reporter: DiagnosticReporter
     ) {
-        val visibilityModifier = source.getChild(KtNodeTypes.MODIFIER_LIST)?.getChild(KtTokens.VISIBILITY_MODIFIERS)
+        val visibilityModifier = source.getChild(KtNodeTypes.MODIFIER_LIST, depth = 1)?.getChild(KtTokens.VISIBILITY_MODIFIERS)
         if (visibilityModifier != null) return
 
         if (explicitVisibilityIsNotRequired(declaration, context)) return

compiler/testData/diagnostics/tests/testsWithExplicitApi/kt56505.kt

@@ -0,0 +1,18 @@
+// FIR_IDENTICAL
+// SKIP_TXT
+// ISSUE: KT-56505
+
+<!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>fun f1<!>() {
+    class LocalClass {
+        public var foo = 0
+    }
+    LocalClass().foo = 1
+}
+
+<!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>class J1<!> {
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>var buf<!>: Int = 0
+        <!GETTER_VISIBILITY_DIFFERS_FROM_PROPERTY_VISIBILITY!>private<!> get() = 42
+        protected set(value) {
+            field = value
+        }
+}

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

@@ -32816,6 +32816,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/interfaces.kt");
             }
 
+            @Test
+            @TestMetadata("kt56505.kt")
+            public void testKt56505() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/testsWithExplicitApi/kt56505.kt");
+            }
+
             @Test
             @TestMetadata("localFunctions.kt")
             public void testLocalFunctions() throws Exception {