JavaClassImpl: add assertion on querying members of light classes

Hopefully this assertion happens before deadlock KT-12966

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/structure/impl/JavaClassImpl.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.load.java.structure.impl
 
+import com.intellij.openapi.diagnostic.Logger
 import com.intellij.psi.PsiClass
 import com.intellij.psi.PsiTypeParameter
 import org.jetbrains.kotlin.asJava.KtLightClassMarker
@@ -63,22 +64,31 @@ class JavaClassImpl(psiClass: PsiClass) : JavaClassifierImpl<PsiClass>(psiClass)
     override val supertypes: Collection<JavaClassifierType>
         get() = classifierTypes(psi.superTypes)
 
-    override // We apply distinct here because PsiClass#getMethods() can return duplicate PSI methods, for example in Lombok (see KT-11778)
+    override val methods: Collection<JavaMethod>
+        get() {
+            assertNotLightClass()
+            // We apply distinct here because PsiClass#getMethods() can return duplicate PSI methods, for example in Lombok (see KT-11778)
             // Return type seems to be null for example for the 'clone' Groovy method generated by @AutoClone (see EA-73795)
-    val methods: Collection<JavaMethod>
+            return methods(psi.methods.filter { method -> !method.isConstructor && method.returnType != null }).distinct()
-        get() = methods(psi.methods.filter { method -> !method.isConstructor && method.returnType != null }).distinct()
+        }
 
-    override // ex. Android plugin generates LightFields for resources started from '.' (.DS_Store file etc)
+    override val fields: Collection<JavaField>
-    val fields: Collection<JavaField>
+        get() {
-        get() = fields(psi.fields.filter { field ->
+            assertNotLightClass()
-            val name = field.name
+            return fields(psi.fields.filter { field ->
-            name != null && Name.isValidIdentifier(name)
+                val name = field.name
-        })
+                // ex. Android plugin generates LightFields for resources started from '.' (.DS_Store file etc)
+                name != null && Name.isValidIdentifier(name)
+            })
+        }
 
-    override // See for example org.jetbrains.plugins.scala.lang.psi.light.ScFunctionWrapper,
+    override val constructors: Collection<JavaConstructor>
+        get() {
+            assertNotLightClass()
+            // See for example org.jetbrains.plugins.scala.lang.psi.light.ScFunctionWrapper,
             // which is present in getConstructors(), but its isConstructor() returns false
-    val constructors: Collection<JavaConstructor>
+            return constructors(psi.constructors.filter { method -> method.isConstructor })
-        get() = constructors(psi.constructors.filter { method -> method.isConstructor })
+        }
 
     override val isAbstract: Boolean
         get() = JavaElementUtil.isAbstract(this)
@@ -93,7 +103,19 @@ class JavaClassImpl(psiClass: PsiClass) : JavaClassifierImpl<PsiClass>(psiClass)
         get() = JavaElementUtil.getVisibility(this)
 
     override val lightClassOriginKind: LightClassOriginKind?
-        get()  = (psi as? KtLightClassMarker)?.originKind
+        get() = (psi as? KtLightClassMarker)?.originKind
 
     override fun getAnnotationOwnerPsi() = psi.modifierList
+
+    private fun assertNotLightClass() {
+        val psiClass = psi
+        if (psiClass !is KtLightClassMarker) return
+
+        val message = "Querying members of JavaClass created for $psiClass of type ${psiClass.javaClass} defined in file ${psiClass.containingFile?.virtualFile?.canonicalPath}"
+        LOGGER.error(message)
+    }
+
+    companion object {
+        private val LOGGER = Logger.getInstance(JavaClassImpl::class.java)
+    }
 }