FIR IDE: fix deadlock in override check

We should not call withFir nestedly as resolving in read action causing deadlocks

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

@@ -43,12 +43,10 @@ internal class KtFirSymbolDeclarationOverridesProvider(
         check(callableSymbol is KtFirSymbol<*>)
         check(containingDeclaration is KtFirClassOrObjectSymbol)
 
-        return callableSymbol.firRef.withFir(FirResolvePhase.IMPLICIT_TYPES_BODY_RESOLVE) { firCallableElement ->
-
-            containingDeclaration.firRef.withFir(FirResolvePhase.IMPLICIT_TYPES_BODY_RESOLVE) { containingDeclaration ->
-
-                val firTypeScope = containingDeclaration.unsubstitutedScope(
-                    containingDeclaration.session,
+        return containingDeclaration.firRef.withFir(FirResolvePhase.IMPLICIT_TYPES_BODY_RESOLVE) { firContainer ->
+            callableSymbol.firRef.withFirUnsafe { firCallableElement ->
+                val firTypeScope = firContainer.unsubstitutedScope(
+                    firContainer.session,
                     ScopeSession(),
                     withForcedTypeCalculator = false
                 )

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/utils/FirRefWithValidityCheck.kt

@@ -41,6 +41,18 @@ internal class FirRefWithValidityCheck<out D : FirDeclaration>(fir: D, resolveSt
         }
     }
 
+    /**
+     * Runs [action] with fir element *without* any lock hold
+     * Consider using this only when you are completely sure
+     * that fir or one of it's container already holds the lock (i.e, corresponding withFir call was made)
+     */
+    inline fun <R> withFirUnsafe(action: (fir: D) -> R): R {
+        token.assertIsValidAndAccessible()
+        val fir = firWeakRef.get()
+            ?: throw EntityWasGarbageCollectedException("FirElement")
+        return action(fir)
+    }
+
     val resolveState
         get() = resolveStateWeakRef.get() ?: throw EntityWasGarbageCollectedException("FirModuleResolveState")