FIR IDE: introduce delegated symbol origin

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/symbols/KtSymbol.kt

@@ -55,4 +55,15 @@ enum class KtSymbolOrigin {
      * The intersection of functions A.foo & B.foo will create a function C.foo which will be marked with [INTERSECTION_OVERRIDE]
      */
     INTERSECTION_OVERRIDE,
+
+    /**
+     * Member symbol which was generated by compiler when using `by` interface delegation
+     * e.g,
+     * ```
+     * interface A { fun x() }
+     * class B(a: A) : A by a
+     * ```
+     * the `B.foo` function will be generated by Kotlin compiler
+     */
+    DELEGATED,
 }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/components/KtFirSymbolContainingDeclarationProvider.kt

@@ -28,6 +28,7 @@ internal class KtFirSymbolContainingDeclarationProvider(
             KtSymbolOrigin.LIBRARY, KtSymbolOrigin.JAVA -> getContainingDeclarationForLibrarySymbol(symbol)
             KtSymbolOrigin.INTERSECTION_OVERRIDE -> TODO()
             KtSymbolOrigin.SAM_CONSTRUCTOR -> TODO()
+            KtSymbolOrigin.DELEGATED -> TODO()
         }
     }
 

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/symbols/KtFirSymbol.kt

@@ -36,6 +36,7 @@ private tailrec fun FirDeclaration.ktSymbolOrigin(): KtSymbolOrigin = when (orig
     FirDeclarationOrigin.SamConstructor -> KtSymbolOrigin.SAM_CONSTRUCTOR
     FirDeclarationOrigin.Enhancement -> KtSymbolOrigin.JAVA
     FirDeclarationOrigin.IntersectionOverride -> KtSymbolOrigin.INTERSECTION_OVERRIDE
+    FirDeclarationOrigin.Delegated -> KtSymbolOrigin.DELEGATED
     else -> {
         val overridden = (this as? FirCallableDeclaration<*>)?.originalIfFakeOverride()
             ?: throw InvalidFirDeclarationOriginForSymbol(this)