diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt
index ca174041a35..42e5cbfc970 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt
@@ -22,12 +22,10 @@ import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
-import org.jetbrains.kotlin.ir.types.IrDynamicType
-import org.jetbrains.kotlin.ir.types.isUnit
-import org.jetbrains.kotlin.ir.types.makeNullable
-import org.jetbrains.kotlin.ir.types.toKotlinType
+import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.isAnnotationClass
 import org.jetbrains.kotlin.ir.util.render
+import org.jetbrains.kotlin.ir.util.superTypes
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitorVoid
 import org.jetbrains.kotlin.resolve.descriptorUtil.isEffectivelyExternal
 import org.jetbrains.kotlin.types.KotlinType
@@ -41,6 +39,7 @@ class CheckIrElementVisitor(
 ) : IrElementVisitorVoid {
 
     val set = mutableSetOf<IrElement>()
+    val checkedTypes = mutableSetOf<IrType>()
 
     override fun visitElement(element: IrElement) {
         if (config.ensureAllNodesAreDifferent) {
@@ -290,4 +289,23 @@ class CheckIrElementVisitor(
         expression.setter?.ensureBound(expression)
     }
 
+    override fun visitExpression(expression: IrExpression) {
+        checkType(expression.type, expression)
+        super.visitExpression(expression)
+    }
+
+    private fun checkType(type: IrType, element: IrElement) {
+        if (type in checkedTypes)
+            return
+
+        when (type) {
+            is IrSimpleType -> {
+                if (!type.classifier.isBound) {
+                    reportError(element, "Type: ${type.render()} has unbound classifier")
+                }
+            }
+        }
+
+        checkedTypes.add(type)
+    }
 }
\ No newline at end of file
diff --git a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/utils/kotlinTypeBasedUtils.kt b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/utils/kotlinTypeBasedUtils.kt
index 7be71d9e39c..a16da585e9d 100644
--- a/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/utils/kotlinTypeBasedUtils.kt
+++ b/compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/utils/kotlinTypeBasedUtils.kt
@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.toIrType
 import org.jetbrains.kotlin.ir.types.toKotlinType
+import org.jetbrains.kotlin.ir.util.SymbolTable
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.CommonSupertypes
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
@@ -23,7 +24,8 @@ fun IrType.isPrimitiveArray() = KotlinBuiltIns.isPrimitiveArray(toKotlinType())
 fun IrType.getPrimitiveArrayElementType() = KotlinBuiltIns.getPrimitiveArrayElementType(toKotlinType())
 
 @Deprecated("Use pure Ir helper")
-fun List<IrType>.commonSupertype() = CommonSupertypes.commonSupertype(map(IrType::toKotlinType)).toIrType()!!
+fun List<IrType>.commonSupertype(symbolTable: SymbolTable) =
+    CommonSupertypes.commonSupertype(map(IrType::toKotlinType)).toIrType(symbolTable)!!
 
 @Deprecated("Use pure Ir helper")
 fun IrType.isSubtypeOf(superType: IrType) = toKotlinType().isSubtypeOf(superType.toKotlinType())
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
index 7933b3552d2..f70deea349f 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
@@ -37,12 +37,7 @@ class AutoboxingTransformer(val context: JsIrBackendContext) : AbstractValueUsag
                 if (this.symbol.owner.let { it is IrSimpleFunction && it.isSuspend }) {
                     irBuiltIns.anyNType
                 } else {
-                    try {
-                        this.symbol.owner.returnType
-                    } catch (e: kotlin.UninitializedPropertyAccessException) {
-                        // TODO: Fix lateinit return types
-                        this.type
-                    }
+                    this.symbol.owner.returnType
                 }
             }
             is IrGetField -> this.symbol.owner.type
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MultipleCatchesLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MultipleCatchesLowering.kt
index 84293a9f0e6..aa77909ea5e 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MultipleCatchesLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MultipleCatchesLowering.kt
@@ -125,7 +125,7 @@ class MultipleCatchesLowering(val context: JsIrBackendContext) : FileLoweringPas
             private fun buildImplicitCast(value: IrExpression, toType: IrType, toTypeSymbol: IrClassifierSymbol) =
                 JsIrBuilder.buildTypeOperator(toType, IrTypeOperator.IMPLICIT_CAST, value, toType, toTypeSymbol)
 
-            private fun mergeTypes(types: List<IrType>) = types.commonSupertype().also {
+            private fun mergeTypes(types: List<IrType>) = types.commonSupertype(context.symbolTable).also {
                 assert(it.isSubtypeOf(context.irBuiltIns.throwableType) || it is IrDynamicType)
             }
 
diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/InlineClasses.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/InlineClasses.kt
index 92c92b04924..1f3e888e3a7 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/InlineClasses.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/InlineClasses.kt
@@ -48,10 +48,6 @@ fun IrType.isInlined(): Boolean = this.getInlinedClass() != null
 private tailrec fun erase(type: IrType): IrClass? {
     val classifier = type.classifierOrFail
 
-    // TODO: Fix unbound symbols
-    if (!classifier.isBound)
-        return null
-
     return when (classifier) {
         is IrClassSymbol -> classifier.owner
         is IrTypeParameterSymbol -> erase(classifier.owner.superTypes.first())