FIR IDE: correctly set symbol origin for fake overridden ones

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/PossiblyFirFakeOverrideSymbol.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.symbols
+
+import org.jetbrains.kotlin.fir.FirSymbolOwner
+import org.jetbrains.kotlin.fir.declarations.FirDeclaration
+
+interface PossiblyFirFakeOverrideSymbol<E, S : FirBasedSymbol<E>> : FirBasedSymbol<E> where E : FirSymbolOwner<E>, E : FirDeclaration {
+    // contract isFakeOverride == true <=> overriddenSymbol != null
+    val isFakeOverride: Boolean
+    val overriddenSymbol: S?
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.fir.symbols.impl
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.symbols.AccessorSymbol
 import org.jetbrains.kotlin.fir.symbols.CallableId
+import org.jetbrains.kotlin.fir.symbols.PossiblyFirFakeOverrideSymbol
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
@@ -23,10 +24,10 @@ sealed class FirFunctionSymbol<D : FirFunction<D>>(
 
 open class FirNamedFunctionSymbol(
     callableId: CallableId,
-    val isFakeOverride: Boolean = false,
+    override val isFakeOverride: Boolean = false,
     // Actual for fake override only
     override val overriddenSymbol: FirNamedFunctionSymbol? = null
-) : FirFunctionSymbol<FirSimpleFunction>(callableId)
+) : FirFunctionSymbol<FirSimpleFunction>(callableId), PossiblyFirFakeOverrideSymbol<FirSimpleFunction, FirNamedFunctionSymbol>
 
 class FirConstructorSymbol(
     callableId: CallableId,

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirVariableSymbol.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.diagnostics.ConeDiagnostic
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.symbols.CallableId
+import org.jetbrains.kotlin.fir.symbols.PossiblyFirFakeOverrideSymbol
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 
@@ -22,10 +23,10 @@ open class FirVariableSymbol<D : FirVariable<D>>(override val callableId: Callab
 
 open class FirPropertySymbol(
     callableId: CallableId,
-    val isFakeOverride: Boolean = false,
+    override val isFakeOverride: Boolean = false,
     // Actual for fake override only
     override val overriddenSymbol: FirPropertySymbol? = null
-) : FirVariableSymbol<FirProperty>(callableId) {
+) : FirVariableSymbol<FirProperty>(callableId), PossiblyFirFakeOverrideSymbol<FirProperty, FirPropertySymbol> {
     // TODO: should we use this constructor for local variables?
     constructor(name: Name) : this(CallableId(name))
 }