From 37a34e12d06fec8edbb6097b38c10ae52ce94447 Mon Sep 17 00:00:00 2001
From: Dmitriy Novozhilov <dmitriy.novozhilov@jetbrains.com>
Date: Fri, 3 Sep 2021 10:04:13 +0300
Subject: [PATCH] [FIR] Make Forced FakeOverrideTypeCalculator thread safe

---
 .../fir/scopes/FakeOverrideTypeCalculator.kt  | 24 ++++++++++++-------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/FakeOverrideTypeCalculator.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/FakeOverrideTypeCalculator.kt
index 4e5e9bff7e1..4ebad2bab99 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/FakeOverrideTypeCalculator.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/scopes/FakeOverrideTypeCalculator.kt
@@ -26,15 +26,21 @@ abstract class FakeOverrideTypeCalculator {
 
     object Forced : FakeOverrideTypeCalculator() {
         override fun computeReturnType(declaration: FirTypedDeclaration): FirResolvedTypeRef {
-            (declaration.returnTypeRef as? FirResolvedTypeRef)?.let { return it }
-            val (substitutor, baseSymbol) = declaration.attributes.fakeOverrideSubstitution ?: error("")
-            val baseDeclaration = baseSymbol.fir as FirTypedDeclaration
-            val baseReturnType = computeReturnType(baseDeclaration).type
-            declaration.attributes.fakeOverrideSubstitution = null
-            val coneType = substitutor.substituteOrSelf(baseReturnType)
-            val returnType = declaration.returnTypeRef.resolvedTypeFromPrototype(coneType)
-            declaration.replaceReturnTypeRef(returnType)
-            return returnType
+            val fakeOverrideSubstitution = declaration.attributes.fakeOverrideSubstitution
+                ?: return declaration.returnTypeRef as FirResolvedTypeRef
+            synchronized(fakeOverrideSubstitution) {
+                if (declaration.attributes.fakeOverrideSubstitution == null) {
+                    return declaration.returnTypeRef as FirResolvedTypeRef
+                }
+                declaration.attributes.fakeOverrideSubstitution = null
+                val (substitutor, baseSymbol) = fakeOverrideSubstitution
+                val baseDeclaration = baseSymbol.fir as FirTypedDeclaration
+                val baseReturnType = computeReturnType(baseDeclaration).type
+                val coneType = substitutor.substituteOrSelf(baseReturnType)
+                val returnType = declaration.returnTypeRef.resolvedTypeFromPrototype(coneType)
+                declaration.replaceReturnTypeRef(returnType)
+                return returnType
+            }
         }
     }
 }