Allow search usages for declarations when correct isEquivalentTo

Now it's possible to do find usages for other languages when light
elements are used.

Revert efb36f4a49 and revise fix of KT-7983:
Don't consider local and non-local class with same fqn equivalent.

 #KT-7983 Fixed

compiler/frontend/src/org/jetbrains/kotlin/psi/KtClass.kt

@@ -50,14 +50,27 @@ open class KtClass : KtClassOrObject {
     fun isInner(): Boolean = hasModifier(KtTokens.INNER_KEYWORD)
 
     override fun isEquivalentTo(another: PsiElement?): Boolean {
-        if (super.isEquivalentTo(another)) {
+        if (this === another) {
             return true
         }
-        if (another is KtClass) {
-            val fq1 = getQualifiedName()
-            val fq2 = another.getQualifiedName()
-            return fq1 != null && fq2 != null && fq1 == fq2
+
+        if (another !is KtClass) {
+            return false
         }
+
+        val fq1 = getQualifiedName() ?: return false
+        val fq2 = another.getQualifiedName() ?: return false
+        if (fq1 == fq2) {
+            val thisLocal = isLocal
+            if (thisLocal != another.isLocal) {
+                return false
+            }
+
+            // For non-local classes same fqn is enough
+            // Consider different instances of local classes non-equivalent
+            return !thisLocal
+        }
+
         return false
     }
 

idea/idea-analysis/src/org/jetbrains/kotlin/idea/references/referenceUtil.kt

@@ -86,7 +86,11 @@ fun PsiReference.matchesTarget(candidateTarget: PsiElement): Boolean {
     }
 
     val targets = unwrappedTargets
-    if (unwrappedCandidate in targets) return true
+
+    val manager = candidateTarget.manager
+    if (targets.any { manager.areElementsEquivalent(unwrappedCandidate, it) }) {
+        return true
+    }
 
     if (element is KtLabelReferenceExpression && (element.parent as? KtContainerNode)?.parent is KtReturnExpression) {
         targets.forEach {
@@ -97,9 +101,6 @@ fun PsiReference.matchesTarget(candidateTarget: PsiElement): Boolean {
         }
     }
 
-    // TODO: Investigate why PsiCompiledElement identity changes
-    if (unwrappedCandidate is PsiCompiledElement && targets.any { it.isEquivalentTo(unwrappedCandidate) }) return true
-
     if (this is KtReference) {
         return targets.any {
             it.isConstructorOf(unwrappedCandidate)