Add reference equality shortcut for equals() in light members

compiler/light-classes/src/org/jetbrains/kotlin/asJava/elements/KtLightFieldImpl.kt

@@ -60,9 +60,10 @@ sealed class KtLightFieldImpl<D : PsiField>(
     }
 
     override fun equals(other: Any?): Boolean =
-            other is KtLightFieldImpl<*> &&
-            this.name == other.name &&
-            this.containingClass == other.containingClass
+            this === other ||
+            (other is KtLightFieldImpl<*> &&
+             this.name == other.name &&
+             this.containingClass == other.containingClass)
 
     override fun hashCode() = 31 * containingClass.hashCode() + name.hashCode()
 

compiler/light-classes/src/org/jetbrains/kotlin/asJava/elements/KtLightMethodImpl.kt

@@ -147,11 +147,12 @@ class KtLightMethodImpl private constructor(
             for source elements index is unique to each member
             */
     override fun equals(other: Any?): Boolean =
-            other is KtLightMethodImpl &&
-            this.name == other.name &&
-            this.containingClass == other.containingClass &&
-            this.lightMemberOrigin == other.lightMemberOrigin &&
-            this._memberIndex == other._memberIndex
+            this === other ||
+            (other is KtLightMethodImpl &&
+             this.name == other.name &&
+             this.containingClass == other.containingClass &&
+             this.lightMemberOrigin == other.lightMemberOrigin &&
+             this._memberIndex == other._memberIndex)
 
     override fun hashCode(): Int = ((getName().hashCode() * 31 + (lightMemberOrigin?.hashCode() ?: 0)) * 31 + containingClass.hashCode()) * 31 + (_memberIndex?.hashCode() ?: 0)