FIR IDE: resolve reference to intersection override member to overridden members

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/KtAnalysisSession.kt

@@ -58,6 +58,9 @@ abstract class KtAnalysisSession(final override val token: ValidityToken) : Vali
     fun KtCallableSymbol.getOverriddenSymbols(containingDeclaration: KtClassOrObjectSymbol): List<KtCallableSymbol> =
         symbolDeclarationOverridesProvider.getOverriddenSymbols(this, containingDeclaration)
 
+    fun KtCallableSymbol.getIntersectionOverriddenSymbols(): Collection<KtCallableSymbol> =
+        symbolDeclarationOverridesProvider.getIntersectionOverriddenSymbols(this)
+
     fun KtExpression.getSmartCasts(): Collection<KtType> = smartCastProvider.getSmartCastedToTypes(this)
 
     fun KtExpression.getImplicitReceiverSmartCasts(): Collection<ImplicitReceiverSmartCast> =

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

@@ -7,7 +7,6 @@ package org.jetbrains.kotlin.idea.frontend.api.components
 
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassOrObjectSymbol
-import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 
 abstract class KtSymbolDeclarationOverridesProvider : KtAnalysisSessionComponent() {
@@ -19,5 +18,9 @@ abstract class KtSymbolDeclarationOverridesProvider : KtAnalysisSessionComponent
         containingDeclaration: KtClassOrObjectSymbol
     ): List<KtCallableSymbol>
 
-    //abstract fun getOverriddenSymbols(callableSymbol: KtCallableSymbol, containingDeclaration: KtClassOrObjectSymbol): List<KtCallableSymbol>
+    /**
+     * If [symbol] origin is [org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbolOrigin.INTERSECTION_OVERRIDE]
+     * Then returns the symbols which [symbol] overrides, otherwise empty collection
+     */
+    abstract fun getIntersectionOverriddenSymbols(symbol: KtCallableSymbol): Collection<KtCallableSymbol>
 }

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

@@ -42,5 +42,17 @@ enum class KtSymbolOrigin {
      */
     JAVA,
 
-    SAM_CONSTRUCTOR
+    SAM_CONSTRUCTOR,
+
+    /**
+     * Consider the following code:
+     * ```
+     * interface A { fun x() }
+     * interface B { fun x() }
+     *
+     * interface C : A, B
+     * ```
+     * The intersection of functions A.foo & B.foo will create a function C.foo which will be marked with [INTERSECTION_OVERRIDE]
+     */
+    INTERSECTION_OVERRIDE,
 }

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

@@ -26,6 +26,7 @@ internal class KtFirSymbolContainingDeclarationProvider(
             KtSymbolOrigin.SOURCE, KtSymbolOrigin.SOURCE_MEMBER_GENERATED ->
                 getContainingDeclarationForKotlinInSourceSymbol(symbol)
             KtSymbolOrigin.LIBRARY, KtSymbolOrigin.JAVA -> getContainingDeclarationForLibrarySymbol(symbol)
+            KtSymbolOrigin.INTERSECTION_OVERRIDE -> TODO()
             KtSymbolOrigin.SAM_CONSTRUCTOR -> TODO()
         }
     }

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

@@ -5,9 +5,15 @@
 
 package org.jetbrains.kotlin.idea.frontend.api.fir.components
 
+import org.jetbrains.kotlin.fir.FirSymbolOwner
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.resolve.ScopeSession
 import org.jetbrains.kotlin.fir.scopes.*
+import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirIntersectionOverrideFunctionSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirIntersectionOverridePropertySymbol
+import org.jetbrains.kotlin.fir.unwrapFakeOverrides
 import org.jetbrains.kotlin.idea.frontend.api.ValidityToken
 import org.jetbrains.kotlin.idea.frontend.api.components.KtSymbolDeclarationOverridesProvider
 import org.jetbrains.kotlin.idea.frontend.api.fir.KtFirAnalysisSession
@@ -63,4 +69,24 @@ internal class KtFirSymbolDeclarationOverridesProvider(
             }
         }
     }
+
+    override fun getIntersectionOverriddenSymbols(symbol: KtCallableSymbol): Collection<KtCallableSymbol> {
+        require(symbol is KtFirSymbol<*>)
+        if (symbol.origin != KtSymbolOrigin.INTERSECTION_OVERRIDE) return emptyList()
+        return symbol.firRef.withFir { fir ->
+            val firSymbol = (fir as? FirSymbolOwner<*>)?.symbol ?: return@withFir emptyList()
+            firSymbol.getIntersectionOverriddenSymbols().map { analysisSession.firSymbolBuilder.buildCallableSymbol(it.fir) }
+        }
+    }
+
+    private fun AbstractFirBasedSymbol<*>.getIntersectionOverriddenSymbols(): Collection<FirCallableSymbol<*>> {
+        require(this is FirCallableSymbol<*>) {
+            "Required FirCallableSymbol but ${this::class} found"
+        }
+        return when (this) {
+            is FirIntersectionOverrideFunctionSymbol -> intersections
+            is FirIntersectionOverridePropertySymbol -> intersections
+            else -> listOf(this)
+        }
+    }
 }

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

@@ -35,6 +35,7 @@ private tailrec fun FirDeclaration.ktSymbolOrigin(): KtSymbolOrigin = when (orig
     FirDeclarationOrigin.Java -> KtSymbolOrigin.JAVA
     FirDeclarationOrigin.SamConstructor -> KtSymbolOrigin.SAM_CONSTRUCTOR
     FirDeclarationOrigin.Enhancement -> KtSymbolOrigin.JAVA
+    FirDeclarationOrigin.IntersectionOverride -> KtSymbolOrigin.INTERSECTION_OVERRIDE
     else -> {
         val overridden = (this as? FirCallableDeclaration<*>)?.originalIfFakeOverride()
             ?: throw InvalidFirDeclarationOriginForSymbol(this)

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/references/KtFirReference.kt

@@ -10,14 +10,32 @@ import org.jetbrains.kotlin.idea.fir.findReferencePsi
 import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
 import org.jetbrains.kotlin.idea.frontend.api.KtSymbolBasedReference
 import org.jetbrains.kotlin.idea.frontend.api.fir.symbols.KtFirSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbolOrigin
 
 interface KtFirReference : KtReference, KtSymbolBasedReference {
-    fun getResolvedToPsi(analysisSession: KtAnalysisSession): Collection<PsiElement> =
+    fun getResolvedToPsi(analysisSession: KtAnalysisSession): Collection<PsiElement> = with(analysisSession) {
-        analysisSession.resolveToSymbols().mapNotNull { symbol ->
+        resolveToSymbols().flatMap { symbol ->
-            (symbol as? KtFirSymbol<*>)?.firRef?.withFir { it.findReferencePsi() }
+            when (symbol) {
-                ?: symbol.psi
+                is KtFirSymbol<*> -> getPsiDeclarations(symbol)
+                else -> listOfNotNull(symbol.psi)
+            }
         }
+    }
+
+    private fun KtAnalysisSession.getPsiDeclarations(symbol: KtFirSymbol<*>): Collection<PsiElement> {
+        val intersectionOverriddenSymbolsOrSingle = when {
+            symbol.origin == KtSymbolOrigin.INTERSECTION_OVERRIDE && symbol is KtCallableSymbol -> symbol.getIntersectionOverriddenSymbols()
+            else -> listOf(symbol)
+        }
+        return intersectionOverriddenSymbolsOrSingle.mapNotNull { it.findPsiForReferenceResolve() }
+    }
+
+    private fun KtSymbol.findPsiForReferenceResolve(): PsiElement? {
+        require(this is KtFirSymbol<*>)
+        return firRef.withFir { it.findReferencePsi() }
+    }
 
     override val resolver get() = KtFirReferenceResolver
 }

idea/idea-frontend-fir/testData/memberScopeByFqName/Int.txt

@@ -1233,7 +1233,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: equals
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -1254,7 +1254,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: hashCode
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -1275,7 +1275,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: toString
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []

idea/idea-frontend-fir/testData/memberScopeByFqName/MutableList.txt

@@ -288,7 +288,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: ABSTRACT
   name: contains
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -309,7 +309,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: ABSTRACT
   name: containsAll
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -372,7 +372,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: ABSTRACT
   name: isEmpty
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -393,7 +393,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: ABSTRACT
   name: iterator
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -439,7 +439,7 @@ KtFirKotlinPropertySymbol:
   isVal: true
   modality: ABSTRACT
   name: size
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   setter: null
   symbolKind: MEMBER
@@ -459,7 +459,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: equals
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -480,7 +480,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: hashCode
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []
@@ -501,7 +501,7 @@ KtFirFunctionSymbol:
   isSuspend: false
   modality: OPEN
   name: toString
-  origin: LIBRARY
+  origin: INTERSECTION_OVERRIDE
   receiverType: null
   symbolKind: MEMBER
   typeParameters: []

idea/testData/resolve/references/SeveralOverrides.kt

@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 interface A {
     fun foo()
 }

idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getMultipleDeclarations.kt

@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 var x : Int <caret>by Baz()
 
 interface Foo {