[IR] Refactoring: Clean-up in ExternalDependenciesGenerator

Note: There is no need to catch KotlinIrLinkerInternalException and
re-throw it as CompilationErrorException since the fix of KT-53649.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/ExternalDependenciesGenerator.kt

@@ -15,44 +15,29 @@
  */
 package org.jetbrains.kotlin.ir.util
 
-import org.jetbrains.kotlin.analyzer.CompilationErrorException
-import org.jetbrains.kotlin.ir.declarations.IrDeclaration
 import org.jetbrains.kotlin.ir.linkage.IrProvider
-import org.jetbrains.kotlin.ir.linkage.KotlinIrLinkerInternalException
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
 
 class ExternalDependenciesGenerator(
-    val symbolTable: SymbolTable,
+    private val symbolTable: SymbolTable,
     private val irProviders: List<IrProvider>
 ) {
-
     fun generateUnboundSymbolsAsDependencies() {
         // There should be at most one DeclarationStubGenerator (none in closed world?)
-        irProviders.singleOrNull { it is DeclarationStubGenerator }?.let {
-            (it as DeclarationStubGenerator).unboundSymbolGeneration = true
-        }
+        irProviders.filterIsInstance<DeclarationStubGenerator>().singleOrNull()?.run { unboundSymbolGeneration = true }
 
         // Deserializing a reference may lead to new unbound references, so we loop until none are left.
-        try {
-            var unbound = setOf<IrSymbol>()
-            do {
-                val prevUnbound = unbound
-                unbound = symbolTable.allUnbound
-                for (symbol in unbound) {
-                    // Symbol could get bound as a side effect of deserializing other symbols.
-                    if (!symbol.isBound) {
-                        irProviders.getDeclaration(symbol)
-                    }
+        var unbound = emptySet<IrSymbol>()
+        do {
+            val prevUnbound = unbound
+            unbound = symbolTable.allUnbound
+            for (symbol in unbound) {
+                // Symbol could get bound as a side effect of deserializing other symbols.
+                if (!symbol.isBound) {
+                    irProviders.firstNotNullOfOrNull { provider -> provider.getDeclaration(symbol) }
                 }
-                // We wait for the unbound to stabilize on fake overrides.
-            } while (unbound != prevUnbound)
-        } catch (ex: KotlinIrLinkerInternalException) {
-            throw CompilationErrorException()
-        }
+            }
+            // We wait for the unbound to stabilize on fake overrides.
+        } while (unbound != prevUnbound)
     }
 }
-
-fun List<IrProvider>.getDeclaration(symbol: IrSymbol): IrDeclaration? =
-    firstNotNullOfOrNull { provider ->
-        provider.getDeclaration(symbol)
-    }