Fix FQ name usage of experimental marker in UseExperimental

#KT-26366 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt

@@ -306,8 +306,11 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
             return false
         }
 
-        private fun PsiElement.isUsageAsUseExperimentalArgument(bindingContext: BindingContext): Boolean =
-            parent is KtClassLiteralExpression &&
+        private fun PsiElement.isUsageAsUseExperimentalArgument(bindingContext: BindingContext): Boolean {
+            val qualifier = (this as? KtSimpleNameExpression)?.getTopmostParentQualifiedExpressionForSelector() ?: this
+            val parent = qualifier.parent
+
+            return parent is KtClassLiteralExpression &&
                     parent.parent is KtValueArgument &&
                     parent.parent.parent is KtValueArgumentList &&
                     parent.parent.parent.parent.let { entry ->
@@ -315,6 +318,7 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
                             annotation.fqName == USE_EXPERIMENTAL_FQ_NAME || annotation.fqName == WAS_EXPERIMENTAL_FQ_NAME
                         } == true
                     }
+        }
     }
 
     class Overrides(project: Project) : DeclarationChecker {

compiler/testData/diagnostics/testsWithStdLib/experimental/fullFqNameUsage.kt

@@ -0,0 +1,12 @@
+// !USE_EXPERIMENTAL: kotlin.Experimental
+
+package test.abc
+
+@Experimental
+annotation class E
+
+@UseExperimental(test.abc.E::class)
+fun f() {}
+
+@test.abc.E
+fun g() {}

compiler/testData/diagnostics/testsWithStdLib/experimental/fullFqNameUsage.txt

@@ -0,0 +1,16 @@
+package
+
+package test {
+
+    package test.abc {
+        @kotlin.UseExperimental(markerClass = {test.abc.E::class}) public fun f(): kotlin.Unit
+        @test.abc.E public fun g(): kotlin.Unit
+
+        @kotlin.Experimental public final annotation class E : kotlin.Annotation {
+            public constructor E()
+            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
+        }
+    }
+}

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

@@ -2422,6 +2422,11 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalUnsignedLiterals.kt");
         }
 
+        @TestMetadata("fullFqNameUsage.kt")
+        public void testFullFqNameUsage() throws Exception {
+            runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/fullFqNameUsage.kt");
+        }
+
         @TestMetadata("importStatement.kt")
         public void testImportStatement() throws Exception {
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/importStatement.kt");

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

@@ -2422,6 +2422,11 @@ public class DiagnosticsTestWithStdLibUsingJavacGenerated extends AbstractDiagno
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalUnsignedLiterals.kt");
         }
 
+        @TestMetadata("fullFqNameUsage.kt")
+        public void testFullFqNameUsage() throws Exception {
+            runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/fullFqNameUsage.kt");
+        }
+
         @TestMetadata("importStatement.kt")
         public void testImportStatement() throws Exception {
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/importStatement.kt");