diff --git a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
index c4df15f4beb..fbdc1a73584 100644
--- a/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
+++ b/compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt
@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.FirElseIfTrueCondition
 import org.jetbrains.kotlin.fir.expressions.FirWhenSubjectExpression
+import org.jetbrains.kotlin.fir.expressions.impl.FirUncheckedNotNullCastImpl
 import org.jetbrains.kotlin.fir.expressions.impl.FirUnitExpression
 import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
 import org.jetbrains.kotlin.fir.references.FirSimpleNamedReference
@@ -990,6 +991,11 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
         }
     }
 
+    private fun FlowContent.generate(makeNotNullCall: FirUncheckedNotNullCastImpl) {
+        generate(makeNotNullCall.expression)
+        keyword("!")
+    }
+
     private fun FlowContent.generate(typeOperatorCall: FirTypeOperatorCall) {
         val (expression) = typeOperatorCall.arguments
         generate(expression)
@@ -1178,6 +1184,7 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
                     generate(expression.expression)
                 }
                 is FirTypeOperatorCall -> generate(expression)
+                is FirUncheckedNotNullCastImpl -> generate(expression)
                 is FirOperatorCall -> generate(expression)
                 else -> inlineUnsupported(expression)
             }
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
index 9247e11845e..e8833fbc3ca 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
@@ -629,6 +629,11 @@ internal class Fir2IrVisitor(
         }
     }
 
+    override fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast, data: Any?): IrElement {
+        // TODO: Ensure correct
+        return uncheckedNotNullCast.expression.toIrExpression()
+    }
+
     override fun visitWrappedArgumentExpression(wrappedArgumentExpression: FirWrappedArgumentExpression, data: Any?): IrElement {
         // TODO: change this temporary hack to something correct
         return wrappedArgumentExpression.expression.toIrExpression()
diff --git a/compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt b/compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt
index 8b131fb5f82..1ffe0552d21 100644
--- a/compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt
+++ b/compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/ConversionUtils.kt
@@ -197,7 +197,10 @@ internal fun FirExpression.generateNotNullOrOther(
         )
         branches += FirWhenBranchImpl(
             session, other.psi, FirElseIfTrueCondition(session, psi),
-            FirSingleExpressionBlock(session, generateResolvedAccessExpression(session, psi, subjectVariable))
+            FirSingleExpressionBlock(
+                session,
+                FirUncheckedNotNullCastImpl(session, psi, generateResolvedAccessExpression(session, psi, subjectVariable))
+            )
         )
     }
 }
diff --git a/compiler/fir/psi2fir/testData/rawBuilder/expressions/nullability.txt b/compiler/fir/psi2fir/testData/rawBuilder/expressions/nullability.txt
index 077f1c780d6..a739cde972b 100644
--- a/compiler/fir/psi2fir/testData/rawBuilder/expressions/nullability.txt
+++ b/compiler/fir/psi2fir/testData/rawBuilder/expressions/nullability.txt
@@ -5,7 +5,7 @@ FILE: nullability.kt
                 Int(42)
             }
             else ->  {
-                R|<local>/<elvis>|
+                R|<local>/<elvis>|!
             }
         }
 
@@ -16,7 +16,7 @@ FILE: nullability.kt
                 throw KotlinNullPointerException#()
             }
             else ->  {
-                R|<local>/<bangbang>|
+                R|<local>/<bangbang>|!
             }
         }
 
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt
index b8cf503079b..495a47c29ac 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt
@@ -131,6 +131,17 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
         }
     }
 
+    override fun transformUncheckedNotNullCast(
+        uncheckedNotNullCast: FirUncheckedNotNullCast,
+        data: Any?
+    ): CompositeTransformResult<FirStatement> {
+        val notNullCast = super.transformUncheckedNotNullCast(uncheckedNotNullCast, data).single as FirUncheckedNotNullCast
+        val resultType = notNullCast.expression.resultType
+        notNullCast.resultType =
+            resultType.withReplacedConeType(session, resultType.coneTypeUnsafe<ConeKotlinType>().withNullability(ConeNullability.NOT_NULL))
+        return notNullCast.compose()
+    }
+
     override fun transformTypeOperatorCall(typeOperatorCall: FirTypeOperatorCall, data: Any?): CompositeTransformResult<FirStatement> {
         val symbolProvider = session.service<FirSymbolProvider>()
         val resolved = super.transformTypeOperatorCall(typeOperatorCall, data).single
diff --git a/compiler/fir/resolve/testData/resolve/stdlib/factoryFunctionOverloads.txt b/compiler/fir/resolve/testData/resolve/stdlib/factoryFunctionOverloads.txt
index ed727668b6b..6f17aff1ab7 100644
--- a/compiler/fir/resolve/testData/resolve/stdlib/factoryFunctionOverloads.txt
+++ b/compiler/fir/resolve/testData/resolve/stdlib/factoryFunctionOverloads.txt
@@ -12,7 +12,7 @@ FILE: factoryFunctionOverloads.kt
                 throw R|kotlin/KotlinNullPointerException.KotlinNullPointerException|()
             }
             else ->  {
-                R|<local>/<bangbang>|
+                R|<local>/<bangbang>|!
             }
         }
         , R|<local>/flag|)
diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt
index 0469d8fb01c..c7a9e7b2567 100644
--- a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt
@@ -919,4 +919,9 @@ class FirRenderer(builder: StringBuilder) : FirVisitorVoid() {
     override fun visitErrorExpression(errorExpression: FirErrorExpression) {
         print("ERROR_EXPR(${errorExpression.reason})")
     }
+
+    override fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast) {
+        uncheckedNotNullCast.expression.accept(this)
+        print("!")
+    }
 }
diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/FirUncheckedNotNullCast.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/FirUncheckedNotNullCast.kt
new file mode 100644
index 00000000000..48c2e05ae91
--- /dev/null
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/FirUncheckedNotNullCast.kt
@@ -0,0 +1,14 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.expressions
+
+import org.jetbrains.kotlin.fir.visitors.FirVisitor
+
+interface FirUncheckedNotNullCast : FirCall {
+    override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitUncheckedNotNullCast(this, data)
+
+    val expression: FirExpression get() = arguments[0]
+}
\ No newline at end of file
diff --git a/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirUncheckedNotNullCastImpl.kt b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirUncheckedNotNullCastImpl.kt
new file mode 100644
index 00000000000..783873411e7
--- /dev/null
+++ b/compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirUncheckedNotNullCastImpl.kt
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.expressions.impl
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirUncheckedNotNullCast
+import org.jetbrains.kotlin.fir.expressions.FirOperation
+import org.jetbrains.kotlin.fir.types.FirTypeRef
+
+class FirUncheckedNotNullCastImpl(
+    session: FirSession,
+    psi: PsiElement?,
+    expression: FirExpression
+) : FirAbstractCall(session, psi), FirUncheckedNotNullCast {
+    init {
+        arguments += expression
+    }
+}
+
diff --git a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirTransformerGenerated.kt b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirTransformerGenerated.kt
index f693dd07550..ed57fbfee5d 100644
--- a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirTransformerGenerated.kt
+++ b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirTransformerGenerated.kt
@@ -236,6 +236,10 @@ abstract class FirTransformer<in D> : FirVisitor<CompositeTransformResult<FirEle
         return transformCall(stringConcatenationCall, data)
     }
 
+    open fun transformUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast, data: D): CompositeTransformResult<FirStatement> {
+        return transformCall(uncheckedNotNullCast, data)
+    }
+
     open fun transformClassReferenceExpression(classReferenceExpression: FirClassReferenceExpression, data: D): CompositeTransformResult<FirStatement> {
         return transformExpression(classReferenceExpression, data)
     }
@@ -732,6 +736,10 @@ abstract class FirTransformer<in D> : FirVisitor<CompositeTransformResult<FirEle
         return transformTypedDeclaration(typedDeclaration, data)
     }
 
+    final override fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast, data: D): CompositeTransformResult<FirElement> {
+        return transformUncheckedNotNullCast(uncheckedNotNullCast, data)
+    }
+
     final override fun visitUserTypeRef(userTypeRef: FirUserTypeRef, data: D): CompositeTransformResult<FirElement> {
         return transformUserTypeRef(userTypeRef, data)
     }
diff --git a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorGenerated.kt b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorGenerated.kt
index b3c31fe081e..d22323dc2f5 100644
--- a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorGenerated.kt
+++ b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorGenerated.kt
@@ -236,6 +236,10 @@ abstract class FirVisitor<out R, in D> {
         return visitCall(stringConcatenationCall, data)
     }
 
+    open fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast, data: D): R {
+        return visitCall(uncheckedNotNullCast, data)
+    }
+
     open fun visitClassReferenceExpression(classReferenceExpression: FirClassReferenceExpression, data: D): R {
         return visitExpression(classReferenceExpression, data)
     }
diff --git a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorVoidGenerated.kt b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorVoidGenerated.kt
index a67c436968e..d1330c056fc 100644
--- a/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorVoidGenerated.kt
+++ b/compiler/fir/tree/visitors/org/jetbrains/kotlin/fir/visitors/FirVisitorVoidGenerated.kt
@@ -236,6 +236,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitCall(stringConcatenationCall, null)
     }
 
+    open fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast) {
+        visitCall(uncheckedNotNullCast, null)
+    }
+
     open fun visitClassReferenceExpression(classReferenceExpression: FirClassReferenceExpression) {
         visitExpression(classReferenceExpression, null)
     }
@@ -732,6 +736,10 @@ abstract class FirVisitorVoid : FirVisitor<Unit, Nothing?>() {
         visitTypedDeclaration(typedDeclaration)
     }
 
+    final override fun visitUncheckedNotNullCast(uncheckedNotNullCast: FirUncheckedNotNullCast, data: Nothing?) {
+        visitUncheckedNotNullCast(uncheckedNotNullCast)
+    }
+
     final override fun visitUserTypeRef(userTypeRef: FirUserTypeRef, data: Nothing?) {
         visitUserTypeRef(userTypeRef)
     }
diff --git a/compiler/testData/ir/irText/expressions/bangbang.fir.txt b/compiler/testData/ir/irText/expressions/bangbang.fir.txt
index bd948b8304b..2711ddf53f8 100644
--- a/compiler/testData/ir/irText/expressions/bangbang.fir.txt
+++ b/compiler/testData/ir/irText/expressions/bangbang.fir.txt
@@ -1,12 +1,12 @@
 FILE fqName:<root> fileName:/bangbang.kt
-  FUN name:test1 visibility:public modality:FINAL <> (a:kotlin.Any?) returnType:kotlin.Any? 
+  FUN name:test1 visibility:public modality:FINAL <> (a:kotlin.Any?) returnType:kotlin.Any
     VALUE_PARAMETER name:a index:0 type:kotlin.Any? 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test1 (a: kotlin.Any?): kotlin.Any? declared in <root>'
-        BLOCK type=kotlin.Any? origin=EXCLEXCL
+      RETURN type=kotlin.Nothing from='public final fun test1 (a: kotlin.Any?): kotlin.Any declared in <root>'
+        BLOCK type=kotlin.Any origin=EXCLEXCL
           VAR name:<bangbang> type:kotlin.Any? [val] 
             GET_VAR 'a: kotlin.Any? declared in <root>.test1' type=kotlin.Any? origin=null
-          WHEN type=kotlin.Any? origin=EXCLEXCL
+          WHEN type=kotlin.Any origin=EXCLEXCL
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val <bangbang>: kotlin.Any? [val] declared in <root>.test1' type=kotlin.Any? origin=null
diff --git a/compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.txt b/compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.txt
index 8c7f3ff6722..f1cb6cbfcfa 100644
--- a/compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.txt
+++ b/compiler/testData/ir/irText/expressions/breakContinueInLoopHeader.fir.txt
@@ -45,11 +45,11 @@ FILE fqName:<root> fileName:/breakContinueInLoopHeader.kt
       WHILE label=L origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=null
-          VAR name:<range> type:kotlin.collections.List<kotlin.String>? [val] 
-            BLOCK type=kotlin.collections.List<kotlin.String>? origin=ELVIS
+          VAR name:<range> type:kotlin.collections.List<kotlin.String> [val]
+            BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
               VAR name:<elvis> type:kotlin.collections.List<kotlin.String>? [val] 
                 GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
-              WHEN type=kotlin.collections.List<kotlin.String>? origin=ELVIS
+              WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
                 BRANCH
                   if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                     arg0: GET_VAR 'val <elvis>: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
@@ -58,24 +58,27 @@ FILE fqName:<root> fileName:/breakContinueInLoopHeader.kt
                 BRANCH
                   if: CONST Boolean type=kotlin.Boolean value=true
                   then: GET_VAR 'val <elvis>: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String>? origin=null
-          VAR name:<iterator> type:IrErrorType [val] 
-            ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [kotlin/collections/List.iterator]>#' type=IrErrorType
+          VAR name:<iterator> type:kotlin.collections.Iterator<kotlin.String> [val]
+            CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=null
+              $this: GET_VAR 'val <range>: kotlin.collections.List<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.List<kotlin.String> origin=null
           WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
-            condition: ERROR_CALL 'Unresolved reference: <Unresolved name: hasNext>#' type=IrErrorType
+            condition: CALL 'public abstract fun hasNext (): kotlin.Boolean declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=null
+              $this: GET_VAR 'val <iterator>: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
             body: BLOCK type=kotlin.Unit origin=null
-              VAR name:s type:IrErrorType [val] 
-                ERROR_CALL 'Unresolved reference: <Unresolved name: next>#' type=IrErrorType
+              VAR name:s type:kotlin.String [val]
+                CALL 'public abstract fun next (): kotlin.String declared in kotlin.collections.Iterator' type=kotlin.String origin=null
+                  $this: GET_VAR 'val <iterator>: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test3' type=kotlin.collections.Iterator<kotlin.String> origin=null
   FUN name:test4 visibility:public modality:FINAL <> (ss:kotlin.collections.List<kotlin.String>?) returnType:kotlin.Unit 
     VALUE_PARAMETER name:ss index:0 type:kotlin.collections.List<kotlin.String>? 
     BLOCK_BODY
       WHILE label=L origin=WHILE_LOOP
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=null
-          VAR name:<range> type:kotlin.collections.List<kotlin.String>? [val] 
-            BLOCK type=kotlin.collections.List<kotlin.String>? origin=ELVIS
+          VAR name:<range> type:kotlin.collections.List<kotlin.String> [val]
+            BLOCK type=kotlin.collections.List<kotlin.String> origin=ELVIS
               VAR name:<elvis> type:kotlin.collections.List<kotlin.String>? [val] 
                 GET_VAR 'ss: kotlin.collections.List<kotlin.String>? declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
-              WHEN type=kotlin.collections.List<kotlin.String>? origin=ELVIS
+              WHEN type=kotlin.collections.List<kotlin.String> origin=ELVIS
                 BRANCH
                   if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                     arg0: GET_VAR 'val <elvis>: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
@@ -84,13 +87,16 @@ FILE fqName:<root> fileName:/breakContinueInLoopHeader.kt
                 BRANCH
                   if: CONST Boolean type=kotlin.Boolean value=true
                   then: GET_VAR 'val <elvis>: kotlin.collections.List<kotlin.String>? [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String>? origin=null
-          VAR name:<iterator> type:IrErrorType [val] 
-            ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [kotlin/collections/List.iterator]>#' type=IrErrorType
+          VAR name:<iterator> type:kotlin.collections.Iterator<kotlin.String> [val]
+            CALL 'public abstract fun iterator (): kotlin.collections.Iterator<kotlin.String> declared in kotlin.collections.List' type=kotlin.collections.Iterator<kotlin.String> origin=null
+              $this: GET_VAR 'val <range>: kotlin.collections.List<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.List<kotlin.String> origin=null
           WHILE label=L2 origin=FOR_LOOP_INNER_WHILE
-            condition: ERROR_CALL 'Unresolved reference: <Unresolved name: hasNext>#' type=IrErrorType
+            condition: CALL 'public abstract fun hasNext (): kotlin.Boolean declared in kotlin.collections.Iterator' type=kotlin.Boolean origin=null
+              $this: GET_VAR 'val <iterator>: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
             body: BLOCK type=kotlin.Unit origin=null
-              VAR name:s type:IrErrorType [val] 
-                ERROR_CALL 'Unresolved reference: <Unresolved name: next>#' type=IrErrorType
+              VAR name:s type:kotlin.String [val]
+                CALL 'public abstract fun next (): kotlin.String declared in kotlin.collections.Iterator' type=kotlin.String origin=null
+                  $this: GET_VAR 'val <iterator>: kotlin.collections.Iterator<kotlin.String> [val] declared in <root>.test4' type=kotlin.collections.Iterator<kotlin.String> origin=null
   FUN name:test5 visibility:public modality:FINAL <> () returnType:kotlin.Unit 
     BLOCK_BODY
       VAR name:i type:kotlin.Int [var] 
diff --git a/compiler/testData/ir/irText/expressions/elvis.fir.txt b/compiler/testData/ir/irText/expressions/elvis.fir.txt
index ad5b94aad96..f6e36b54a60 100644
--- a/compiler/testData/ir/irText/expressions/elvis.fir.txt
+++ b/compiler/testData/ir/irText/expressions/elvis.fir.txt
@@ -12,15 +12,15 @@ FILE fqName:<root> fileName:/elvis.kt
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun foo (): kotlin.Any? declared in <root>'
         CONST Null type=kotlin.Nothing? value=null
-  FUN name:test1 visibility:public modality:FINAL <> (a:kotlin.Any?, b:kotlin.Any) returnType:kotlin.Any? 
+  FUN name:test1 visibility:public modality:FINAL <> (a:kotlin.Any?, b:kotlin.Any) returnType:kotlin.Any
     VALUE_PARAMETER name:a index:0 type:kotlin.Any? 
     VALUE_PARAMETER name:b index:1 type:kotlin.Any 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test1 (a: kotlin.Any?, b: kotlin.Any): kotlin.Any? declared in <root>'
-        BLOCK type=kotlin.Any? origin=ELVIS
+      RETURN type=kotlin.Nothing from='public final fun test1 (a: kotlin.Any?, b: kotlin.Any): kotlin.Any declared in <root>'
+        BLOCK type=kotlin.Any origin=ELVIS
           VAR name:<elvis> type:kotlin.Any? [val] 
             GET_VAR 'a: kotlin.Any? declared in <root>.test1' type=kotlin.Any? origin=null
-          WHEN type=kotlin.Any? origin=ELVIS
+          WHEN type=kotlin.Any origin=ELVIS
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test1' type=kotlin.Any? origin=null
@@ -29,15 +29,15 @@ FILE fqName:<root> fileName:/elvis.kt
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
               then: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test1' type=kotlin.Any? origin=null
-  FUN name:test2 visibility:public modality:FINAL <> (a:kotlin.String?, b:kotlin.Any) returnType:kotlin.Any? 
+  FUN name:test2 visibility:public modality:FINAL <> (a:kotlin.String?, b:kotlin.Any) returnType:kotlin.Any
     VALUE_PARAMETER name:a index:0 type:kotlin.String? 
     VALUE_PARAMETER name:b index:1 type:kotlin.Any 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test2 (a: kotlin.String?, b: kotlin.Any): kotlin.Any? declared in <root>'
-        BLOCK type=kotlin.Any? origin=ELVIS
+      RETURN type=kotlin.Nothing from='public final fun test2 (a: kotlin.String?, b: kotlin.Any): kotlin.Any declared in <root>'
+        BLOCK type=kotlin.Any origin=ELVIS
           VAR name:<elvis> type:kotlin.String? [val] 
             GET_VAR 'a: kotlin.String? declared in <root>.test2' type=kotlin.String? origin=null
-          WHEN type=kotlin.Any? origin=ELVIS
+          WHEN type=kotlin.Any origin=ELVIS
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val <elvis>: kotlin.String? [val] declared in <root>.test2' type=kotlin.String? origin=null
@@ -75,14 +75,14 @@ FILE fqName:<root> fileName:/elvis.kt
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
               then: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test3' type=kotlin.Any? origin=null
-  FUN name:test4 visibility:public modality:FINAL <> (x:kotlin.Any) returnType:kotlin.Any? 
+  FUN name:test4 visibility:public modality:FINAL <> (x:kotlin.Any) returnType:kotlin.Any
     VALUE_PARAMETER name:x index:0 type:kotlin.Any 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test4 (x: kotlin.Any): kotlin.Any? declared in <root>'
-        BLOCK type=kotlin.Any? origin=ELVIS
+      RETURN type=kotlin.Nothing from='public final fun test4 (x: kotlin.Any): kotlin.Any declared in <root>'
+        BLOCK type=kotlin.Any origin=ELVIS
           VAR name:<elvis> type:kotlin.Any? [val] 
             CALL 'public final fun <get-p> (): kotlin.Any? declared in <root>' type=kotlin.Any? origin=null
-          WHEN type=kotlin.Any? origin=ELVIS
+          WHEN type=kotlin.Any origin=ELVIS
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test4' type=kotlin.Any? origin=null
@@ -91,14 +91,14 @@ FILE fqName:<root> fileName:/elvis.kt
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
               then: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test4' type=kotlin.Any? origin=null
-  FUN name:test5 visibility:public modality:FINAL <> (x:kotlin.Any) returnType:kotlin.Any? 
+  FUN name:test5 visibility:public modality:FINAL <> (x:kotlin.Any) returnType:kotlin.Any
     VALUE_PARAMETER name:x index:0 type:kotlin.Any 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test5 (x: kotlin.Any): kotlin.Any? declared in <root>'
-        BLOCK type=kotlin.Any? origin=ELVIS
+      RETURN type=kotlin.Nothing from='public final fun test5 (x: kotlin.Any): kotlin.Any declared in <root>'
+        BLOCK type=kotlin.Any origin=ELVIS
           VAR name:<elvis> type:kotlin.Any? [val] 
             CALL 'public final fun foo (): kotlin.Any? declared in <root>' type=kotlin.Any? origin=null
-          WHEN type=kotlin.Any? origin=ELVIS
+          WHEN type=kotlin.Any origin=ELVIS
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val <elvis>: kotlin.Any? [val] declared in <root>.test5' type=kotlin.Any? origin=null
diff --git a/compiler/testData/ir/irText/expressions/floatingPointComparisons/eqeqRhsConditionPossiblyAffectingLhs.fir.txt b/compiler/testData/ir/irText/expressions/floatingPointComparisons/eqeqRhsConditionPossiblyAffectingLhs.fir.txt
index 3d5449df675..b0fd0b73521 100644
--- a/compiler/testData/ir/irText/expressions/floatingPointComparisons/eqeqRhsConditionPossiblyAffectingLhs.fir.txt
+++ b/compiler/testData/ir/irText/expressions/floatingPointComparisons/eqeqRhsConditionPossiblyAffectingLhs.fir.txt
@@ -5,14 +5,14 @@ FILE fqName:<root> fileName:/eqeqRhsConditionPossiblyAffectingLhs.kt
       RETURN type=kotlin.Nothing from='public final fun test (x: kotlin.Any): kotlin.Boolean declared in <root>'
         CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
           arg0: GET_VAR 'x: kotlin.Any declared in <root>.test' type=kotlin.Any origin=null
-          arg1: WHEN type=kotlin.Any? origin=IF
+          arg1: WHEN type=kotlin.Any origin=IF
             BRANCH
               if: TYPE_OP type=kotlin.Boolean origin=NOT_INSTANCEOF typeOperand=kotlin.Double
                 GET_VAR 'x: kotlin.Any declared in <root>.test' type=kotlin.Any origin=null
-              then: BLOCK type=kotlin.Nothing? origin=EXCLEXCL
+              then: BLOCK type=kotlin.Nothing origin=EXCLEXCL
                 VAR name:<bangbang> type:kotlin.Nothing? [val] 
                   CONST Null type=kotlin.Nothing? value=null
-                WHEN type=kotlin.Nothing? origin=EXCLEXCL
+                WHEN type=kotlin.Nothing origin=EXCLEXCL
                   BRANCH
                     if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                       arg0: GET_VAR 'val <bangbang>: kotlin.Nothing? [val] declared in <root>.test' type=kotlin.Nothing? origin=null