Implement equivalence of light members by origin when possible

Previous implementation worked through equality that used equality
of method stubs (see LightMemberOriginForCompiledMethod). But method
stubs for compiled element can be recreated when caches are outdated,
including weak reference cleaning (see ClsJavaStubByVirtualFileCache).

This could cause misbehave of find usages when java reference has an
outdated version of light element in resolution cache.

compiler/light-classes/src/org/jetbrains/kotlin/asJava/builder/LightElementOrigin.kt

@@ -50,10 +50,16 @@ interface LightMemberOrigin : LightElementOrigin {
     override val originalElement: KtDeclaration?
     override val originKind: JvmDeclarationOriginKind
 
+    fun isEquivalentTo(other: LightMemberOrigin?): Boolean
     fun copy(): LightMemberOrigin
 }
 
 data class LightMemberOriginForDeclaration(override val originalElement: KtDeclaration, override val originKind: JvmDeclarationOriginKind) : LightMemberOrigin {
+    override fun isEquivalentTo(other: LightMemberOrigin?): Boolean {
+        if (other !is LightMemberOriginForDeclaration) return false
+        return originalElement.isEquivalentTo(other.originalElement)
+    }
+
     override fun copy(): LightMemberOrigin {
         return LightMemberOriginForDeclaration(originalElement.copy() as KtDeclaration, originKind)
     }

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

@@ -70,13 +70,6 @@ sealed class KtLightFieldImpl<D : PsiField>(
         return (clsDelegate as PsiVariableEx).computeConstantValue(visitedVars)
     }
 
-    override fun isEquivalentTo(another: PsiElement?): Boolean {
-        if (another is KtLightField && this == another) {
-            return true
-        }
-        return super.isEquivalentTo(another)
-    }
-
     override fun copy() = Factory.create(lightMemberOrigin?.copy(), clsDelegate, containingClass)
 
 

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

@@ -64,6 +64,14 @@ abstract class KtLightMemberImpl<out D : PsiMember>(
     override fun getDocComment() = (clsDelegate as PsiDocCommentOwner).docComment
 
     override fun isDeprecated() = (clsDelegate as PsiDocCommentOwner).isDeprecated
+
+    override fun isEquivalentTo(another: PsiElement?): Boolean {
+        val isEquivalentByOrigin =
+                another is KtLightMember<*> &&
+                lightMemberOrigin?.isEquivalentTo(another.lightMemberOrigin) == true
+
+        return isEquivalentByOrigin || this == another
+    }
 }
 
 internal fun getMemberOrigin(member: PsiMember): LightMemberOriginForDeclaration? {

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

@@ -139,14 +139,6 @@ class KtLightMethodImpl private constructor(
         return typeParameters.all { processor.execute(it, state) }
     }
 
-    override fun isEquivalentTo(another: PsiElement?): Boolean {
-        if (another is KtLightMethod && this == another) {
-            return true
-        }
-
-        return super.isEquivalentTo(another)
-    }
-
     private val _memberIndex: MemberIndex?
         get() = (dummyDelegate ?: clsDelegate).memberIndex