diff --git a/compiler/psi/src/org/jetbrains/kotlin/psi/KtPsiFactory.kt b/compiler/psi/src/org/jetbrains/kotlin/psi/KtPsiFactory.kt
index 973e521e823..f0e3f93c017 100644
--- a/compiler/psi/src/org/jetbrains/kotlin/psi/KtPsiFactory.kt
+++ b/compiler/psi/src/org/jetbrains/kotlin/psi/KtPsiFactory.kt
@@ -19,6 +19,8 @@ import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.ImportPath
+import org.jetbrains.kotlin.utils.KotlinExceptionWithAttachments
+import org.jetbrains.kotlin.utils.checkWithAttachment
 
 @JvmOverloads
 fun KtPsiFactory(project: Project?, markGenerated: Boolean = true): KtPsiFactory = KtPsiFactory(project!!, markGenerated)
@@ -299,7 +301,12 @@ class KtPsiFactory @JvmOverloads constructor(private val project: Project, val m
     fun <TDeclaration : KtDeclaration> createDeclaration(text: String): TDeclaration {
         val file = createFile(text)
         val declarations = file.declarations
-        assert(declarations.size == 1) { "${declarations.size} declarations in $text" }
+        checkWithAttachment(declarations.size == 1, { "unexpected ${declarations.size} declarations" }) {
+            it.withAttachment("text.kt", text)
+            for (d in declarations.withIndex()) {
+                it.withAttachment("declaration${d.index}.kt", d.value.text)
+            }
+        }
         @Suppress("UNCHECKED_CAST")
         return declarations.first() as TDeclaration
     }
diff --git a/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt b/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
index d9697ccc25d..ef70c0a200e 100644
--- a/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
+++ b/compiler/util/src/org/jetbrains/kotlin/utils/KotlinExceptionWithAttachments.kt
@@ -26,3 +26,11 @@ open class KotlinExceptionWithAttachments : RuntimeException, ExceptionWithAttac
         return this
     }
 }
+
+inline fun checkWithAttachment(value: Boolean, lazyMessage: () -> String, attachments: (KotlinExceptionWithAttachments) -> Unit = {}) {
+    if (!value) {
+        val e = KotlinExceptionWithAttachments(lazyMessage())
+        attachments(e)
+        throw e
+    }
+}
diff --git a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRenderer.kt b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRenderer.kt
index f927f789ca0..a3f14910fff 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRenderer.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRenderer.kt
@@ -251,6 +251,7 @@ interface DescriptorRendererOptions {
     var parameterNamesInFunctionalTypes: Boolean
     var renderFunctionContracts: Boolean
     var presentableUnresolvedTypes: Boolean
+    var informativeErrorType: Boolean
 }
 
 object ExcludedTypeAnnotations {
diff --git a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt
index 8f2b2c7dbc3..1412e6590c1 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.kt
@@ -244,7 +244,11 @@ internal class DescriptorRendererImpl(
             if (type is UnresolvedType && presentableUnresolvedTypes) {
                 append(type.presentableName)
             } else {
-                append(type.constructor.toString()) // Debug name of an error type is more informative
+                if (type is ErrorType && !informativeErrorType) {
+                    append(type.presentableName)
+                } else {
+                    append(type.constructor.toString()) // Debug name of an error type is more informative
+                }
             }
             append(renderTypeArguments(type.arguments))
         } else {
diff --git a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererOptionsImpl.kt b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererOptionsImpl.kt
index a225767bf80..9938968baee 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererOptionsImpl.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererOptionsImpl.kt
@@ -127,4 +127,6 @@ internal class DescriptorRendererOptionsImpl : DescriptorRendererOptions {
     override var presentableUnresolvedTypes: Boolean by property(false)
 
     override var boldOnlyForNamesInHtml: Boolean by property(false)
+
+    override var informativeErrorType: Boolean by property(true)
 }
diff --git a/core/descriptors/src/org/jetbrains/kotlin/types/ErrorType.kt b/core/descriptors/src/org/jetbrains/kotlin/types/ErrorType.kt
index f07d2ede12b..da4301118e9 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/types/ErrorType.kt
+++ b/core/descriptors/src/org/jetbrains/kotlin/types/ErrorType.kt
@@ -22,10 +22,11 @@ import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner
 import org.jetbrains.kotlin.types.refinement.TypeRefinement
 
 open class ErrorType @JvmOverloads internal constructor(
-        override val constructor: TypeConstructor,
-        override val memberScope: MemberScope,
-        override val arguments: List<TypeProjection> = emptyList(),
-        override val isMarkedNullable: Boolean = false
+    override val constructor: TypeConstructor,
+    override val memberScope: MemberScope,
+    override val arguments: List<TypeProjection> = emptyList(),
+    override val isMarkedNullable: Boolean = false,
+    open val presentableName: String = "???"
 ) : SimpleType() {
     override val annotations: Annotations
         get() = Annotations.EMPTY
@@ -43,14 +44,14 @@ open class ErrorType @JvmOverloads internal constructor(
 }
 
 class UnresolvedType(
-        val presentableName: String,
-        constructor: TypeConstructor,
-        memberScope: MemberScope,
-        arguments: List<TypeProjection>,
-        isMarkedNullable: Boolean
+    override val presentableName: String,
+    constructor: TypeConstructor,
+    memberScope: MemberScope,
+    arguments: List<TypeProjection>,
+    isMarkedNullable: Boolean
 ) : ErrorType(constructor, memberScope, arguments, isMarkedNullable) {
     override fun makeNullableAsSpecified(newNullability: Boolean): SimpleType =
-            UnresolvedType(presentableName, constructor, memberScope, arguments, newNullability)
+        UnresolvedType(presentableName, constructor, memberScope, arguments, newNullability)
 
     @TypeRefinement
     override fun refine(kotlinTypeRefiner: KotlinTypeRefiner) = this
diff --git a/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt b/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
index 6dcf81e2361..b7297c0b0b4 100644
--- a/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
+++ b/idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/ToFromOriginalFileMapper.kt
@@ -21,7 +21,7 @@ import com.intellij.psi.PsiElement
 import com.intellij.psi.util.PsiTreeUtil
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
-import org.jetbrains.kotlin.utils.KotlinExceptionWithAttachments
+import org.jetbrains.kotlin.utils.checkWithAttachment
 import kotlin.math.min
 
 class ToFromOriginalFileMapper private constructor(
@@ -49,12 +49,11 @@ class ToFromOriginalFileMapper private constructor(
         val syntheticText = syntheticFile.text
         val originalSubSequence = originalText.subSequence(0, completionOffset)
         val syntheticSubSequence = syntheticText.subSequence(0, completionOffset)
-        if (originalSubSequence != syntheticSubSequence) {
-            throw KotlinExceptionWithAttachments(
-                "original subText [len: ${originalSubSequence.length}]" +
-                        " does not match synthetic subText [len: ${syntheticSubSequence.length}]"
-            )
-                .withAttachment("original subText", originalSubSequence.toString())
+        checkWithAttachment(originalSubSequence == syntheticSubSequence, {
+            "original subText [len: ${originalSubSequence.length}]" +
+                    " does not match synthetic subText [len: ${syntheticSubSequence.length}]"
+        }) {
+            it.withAttachment("original subText", originalSubSequence.toString())
                 .withAttachment("synthetic subText", syntheticSubSequence.toString())
         }
 
diff --git a/idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt b/idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt
index 67fb8b957b2..4fe18499d29 100644
--- a/idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt
+++ b/idea/idea-core/src/org/jetbrains/kotlin/idea/core/overrideImplement/OverrideMemberChooserObject.kt
@@ -223,8 +223,10 @@ private val OVERRIDE_RENDERER = withOptions {
         it.type.constructor.declarationDescriptor?.annotations?.hasAnnotation(ExperimentalUsageChecker.EXPERIMENTAL_FQ_NAME) ?: false
     }
     presentableUnresolvedTypes = true
+    informativeErrorType = false
 }
 
+
 private val EXPECT_RENDERER = OVERRIDE_RENDERER.withOptions {
     modifiers = setOf(VISIBILITY, MODALITY, OVERRIDE, INNER, MEMBER_KIND)
     renderConstructorKeyword = false