[lc] decompiled: make isEquivalentTo lightweight

^KT-53934 Fixed

analysis/decompiled/light-classes-for-decompiled/src/org/jetbrains/kotlin/analysis/decompiled/light/classes/KtLightFieldForDecompiledDeclaration.kt

@@ -71,4 +71,10 @@ open class KtLightFieldForDecompiledDeclaration(
     override fun toString(): String = "${this.javaClass.simpleName} of $fldParent"
 
     override fun isValid(): Boolean = parent.isValid
+
+    override fun isEquivalentTo(another: PsiElement?): Boolean {
+        return this == another ||
+                another is KtLightFieldForDecompiledDeclaration && fldDelegate.isEquivalentTo(another.fldDelegate) ||
+                fldDelegate.isEquivalentTo(another)
+    }
 }

analysis/decompiled/light-classes-for-decompiled/src/org/jetbrains/kotlin/analysis/decompiled/light/classes/KtLightMethodForDecompiledDeclaration.kt

@@ -103,6 +103,12 @@ class KtLightMethodForDecompiledDeclaration(
     override fun isValid(): Boolean = parent.isValid
 
     override fun getOriginalElement() = funDelegate
+
+    override fun isEquivalentTo(another: PsiElement?): Boolean {
+        return this == another ||
+                another is KtLightMethodForDecompiledDeclaration && funDelegate.isEquivalentTo(another.funDelegate) ||
+                funDelegate.isEquivalentTo(another)
+    }
 }
 
 private fun KtLightMethod.checkIsMangled(): Boolean {