diff --git a/compiler/testData/loadJava/compiledJava/PrivateMembers.txt b/compiler/testData/loadJava/compiledJava/PrivateMembers.txt
index 93350ea65b4..2b006cb7ab3 100644
--- a/compiler/testData/loadJava/compiledJava/PrivateMembers.txt
+++ b/compiler/testData/loadJava/compiledJava/PrivateMembers.txt
@@ -4,7 +4,7 @@ public open class PrivateMembers {
     private constructor PrivateMembers()
     private final var field: kotlin.Int
     private open fun method(): kotlin.Unit
-    private final /*synthesized*/ fun samAdapter(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+    private final /*synthesized*/ fun samAdapter(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
     private open fun samAdapter(/*0*/ p0: test.PrivateMembers.SamInterface!): kotlin.Unit
 
     private open inner class Inner {
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/AmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/AmbiguousAdapters.txt
index 3d69c69d4ab..67cd27aa493 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/AmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/AmbiguousAdapters.txt
@@ -2,8 +2,8 @@ package test
 
 public open class AmbiguousAdapters {
     public constructor AmbiguousAdapters()
-    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
     public open fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
     public open fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/Basic.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/Basic.txt
index 1b625560c37..9efc9eb02fd 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/Basic.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/Basic.txt
@@ -2,10 +2,10 @@ package test
 
 public open class Basic {
     public constructor Basic()
-    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+    public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
     public open fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
 
     // Static members
-    public /*synthesized*/ fun bar(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+    public /*synthesized*/ fun bar(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
     public open fun bar(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/Constructor.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/Constructor.txt
index feb9f32a186..f85e89a2c92 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/Constructor.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/Constructor.txt
@@ -1,6 +1,6 @@
 package test
 
 public open class Constructor {
-    public /*synthesized*/ constructor Constructor(/*0*/ p0: (() -> kotlin.Unit)?)
+    public /*synthesized*/ constructor Constructor(/*0*/ p0: (() -> kotlin.Unit)!)
     public constructor Constructor(/*0*/ p0: java.lang.Runnable!)
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
index 54d28bed348..486644c6f33 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
@@ -3,16 +3,16 @@ package test
 public trait DeepSamLoop {
     
     public trait Bar {
-        public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Bar?) -> kotlin.Unit)?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Bar!) -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: test.DeepSamLoop.Foo!): kotlin.Unit
     }
     
     public trait Foo {
-        public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Foo?) -> kotlin.Unit)?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Foo!) -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: test.DeepSamLoop.Bar!): kotlin.Unit
     }
     
     // Static members
-    public final /*synthesized*/ fun Bar(/*0*/ function: (test.DeepSamLoop.Foo?) -> kotlin.Unit): test.DeepSamLoop.Bar
-    public final /*synthesized*/ fun Foo(/*0*/ function: (test.DeepSamLoop.Bar?) -> kotlin.Unit): test.DeepSamLoop.Foo
+    public /*synthesized*/ fun Bar(/*0*/ function: (test.DeepSamLoop.Foo!) -> kotlin.Unit): test.DeepSamLoop.Bar
+    public /*synthesized*/ fun Foo(/*0*/ function: (test.DeepSamLoop.Bar!) -> kotlin.Unit): test.DeepSamLoop.Foo
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/NonTrivialFunctionType.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/NonTrivialFunctionType.txt
index 33efd145f30..e8338dfd6b2 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/NonTrivialFunctionType.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/NonTrivialFunctionType.txt
@@ -2,11 +2,11 @@ package test
 
 public open class NonTrivialFunctionType {
     public constructor NonTrivialFunctionType()
-    public final /*synthesized*/ fun foo(/*0*/ p0: ((java.io.File, kotlin.String) -> kotlin.Boolean)?): kotlin.Unit
-    public final /*synthesized*/ fun foo(/*0*/ p0: ((kotlin.String, kotlin.String) -> kotlin.Int)?): kotlin.Unit
+    public final /*synthesized*/ fun foo(/*0*/ p0: ((java.io.File!, kotlin.String!) -> kotlin.Boolean)!): kotlin.Unit
+    public final /*synthesized*/ fun foo(/*0*/ p0: ((kotlin.String!, kotlin.String!) -> kotlin.Int)!): kotlin.Unit
     public open fun foo(/*0*/ p0: java.io.FilenameFilter!): kotlin.Unit
     public open fun foo(/*0*/ p0: java.util.Comparator<kotlin.String!>!): kotlin.Unit
-    public final /*synthesized*/ fun wildcardBound(/*0*/ p0: ((kotlin.CharSequence?, kotlin.CharSequence?) -> kotlin.Int)?): kotlin.Unit
+    public final /*synthesized*/ fun wildcardBound(/*0*/ p0: ((kotlin.CharSequence!, kotlin.CharSequence!) -> kotlin.Int)!): kotlin.Unit
     public open fun wildcardBound(/*0*/ p0: java.util.Comparator<in kotlin.CharSequence!>!): kotlin.Unit
     public open fun wildcardUnbound(/*0*/ p0: java.util.Comparator<out kotlin.Any?>!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
index 8f020ab7ded..f76631190fd 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
@@ -3,15 +3,15 @@ package test
 public trait AdapterDoesntOverrideDeclaration {
     
     public trait Sub : test.AdapterDoesntOverrideDeclaration.Super {
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
     public trait Super {
-        public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
     }
     
     // Static members
-    public final /*synthesized*/ fun Super(/*0*/ function: ((() -> kotlin.Unit)?) -> kotlin.Unit): test.AdapterDoesntOverrideDeclaration.Super
+    public /*synthesized*/ fun Super(/*0*/ function: ((() -> kotlin.Unit!)!) -> kotlin.Unit): test.AdapterDoesntOverrideDeclaration.Super
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
index c0cbf63458a..d41e90271e4 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
@@ -3,14 +3,14 @@ package test
 public trait InheritedAdapterAndDeclaration {
 
     public trait Sub : test.InheritedAdapterAndDeclaration.Super {
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public trait Super {
-        public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
index 7970c379294..85b21f7a92c 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
@@ -3,16 +3,16 @@ package test
 public trait InheritedAmbiguousAdapters {
 
     public trait Sub : test.InheritedAmbiguousAdapters.Super {
-        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public trait Super {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
index d1126be6ee6..d26fcd92cfc 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
@@ -3,16 +3,16 @@ package test
 public trait InheritedAndOverriddenAmbiguousAdapters {
 
     public trait Sub : test.InheritedAndOverriddenAmbiguousAdapters.Super {
-        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final override /*1*/ /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract override /*1*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public final override /*1*/ /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract override /*1*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public trait Super {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
index d2279264b80..56df91abef0 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
@@ -4,13 +4,13 @@ public trait InheritedOverridden {
 
     public open class Sub : test.InheritedOverridden.Super {
         public constructor Sub()
-        public final override /*1*/ /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public open override /*1*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final override /*1*/ /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public open override /*1*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public open class Super {
         public constructor Super()
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public open fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public open fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
index 5f0950d43b6..42b12e26641 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
@@ -4,13 +4,13 @@ public trait InheritedOverriddenAdapter {
 
     public open class Sub : test.InheritedOverriddenAdapter.Super {
         public constructor Sub()
-        public open override /*1*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public open override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public open override /*1*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
+        public open override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public open class Super {
         public constructor Super()
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public open fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public open fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
index 978fc13d436..655dcb3b2f3 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
@@ -3,22 +3,22 @@ package test
 public trait InheritedSameAdapters {
     
     public trait Sub : test.InheritedSameAdapters.Super1, test.InheritedSameAdapters.Super2 {
-        public final override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
     public trait Super1 {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
     public trait Super2 {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
     // Static members
-    public final /*synthesized*/ fun Sub(/*0*/ function: (java.lang.Runnable?) -> kotlin.Unit): test.InheritedSameAdapters.Sub
-    public final /*synthesized*/ fun Super1(/*0*/ function: (java.lang.Runnable?) -> kotlin.Unit): test.InheritedSameAdapters.Super1
-    public final /*synthesized*/ fun Super2(/*0*/ function: (java.lang.Runnable?) -> kotlin.Unit): test.InheritedSameAdapters.Super2
+    public /*synthesized*/ fun Sub(/*0*/ function: (java.lang.Runnable!) -> kotlin.Unit): test.InheritedSameAdapters.Sub
+    public /*synthesized*/ fun Super1(/*0*/ function: (java.lang.Runnable!) -> kotlin.Unit): test.InheritedSameAdapters.Super1
+    public /*synthesized*/ fun Super2(/*0*/ function: (java.lang.Runnable!) -> kotlin.Unit): test.InheritedSameAdapters.Super2
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
index cf43fe3ad8e..c7111364b59 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
@@ -3,12 +3,12 @@ package test
 public trait InheritedSimple {
     
     public trait Sub : test.InheritedSimple.Super {
-        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+        public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
     public trait Super {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
     
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
index 6af72f2b45e..153434ee896 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
@@ -3,15 +3,15 @@ package test
 public trait OverriddenAmbiguousAdapters {
 
     public trait Sub : test.OverriddenAmbiguousAdapters.Super {
-        public abstract override /*2*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public abstract override /*2*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
     public trait Super {
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.io.Closeable?): kotlin.Unit
-        public abstract fun foo(/*0*/ p0: java.lang.Runnable?): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
+        public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 }
diff --git a/core/descriptor.loader.java/src/org/jetbrains/jet/lang/resolve/java/sam/SingleAbstractMethodUtils.java b/core/descriptor.loader.java/src/org/jetbrains/jet/lang/resolve/java/sam/SingleAbstractMethodUtils.java
index 5d040ed2fa9..b4de0b638f0 100644
--- a/core/descriptor.loader.java/src/org/jetbrains/jet/lang/resolve/java/sam/SingleAbstractMethodUtils.java
+++ b/core/descriptor.loader.java/src/org/jetbrains/jet/lang/resolve/java/sam/SingleAbstractMethodUtils.java
@@ -22,6 +22,7 @@ import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.descriptors.annotations.Annotations;
 import org.jetbrains.jet.lang.descriptors.impl.TypeParameterDescriptorImpl;
 import org.jetbrains.jet.lang.descriptors.impl.ValueParameterDescriptorImpl;
+import org.jetbrains.jet.lang.resolve.java.JavaPackage;
 import org.jetbrains.jet.lang.resolve.java.descriptor.*;
 import org.jetbrains.jet.lang.resolve.java.resolver.DescriptorResolverUtils;
 import org.jetbrains.jet.lang.resolve.java.structure.*;
@@ -82,7 +83,7 @@ public class SingleAbstractMethodUtils {
     }
 
     @Nullable
-    private static JetType getFunctionTypeForSamType(@NotNull JetType samType) {
+    private static JetType getFunctionTypeForSamType(@NotNull JetType samType, boolean isSamConstructor) {
         // e.g. samType == Comparator<String>?
 
         ClassifierDescriptor classifier = samType.getConstructor().getDeclarationDescriptor();
@@ -94,7 +95,16 @@ public class SingleAbstractMethodUtils {
                 // Function2<String, String, Int>?
                 JetType substitute = TypeSubstitutor.create(samType).substitute(functionTypeDefault, Variance.INVARIANT);
 
-                return substitute == null ? null : fixProjections(TypeUtils.makeNullableAsSpecified(substitute, samType.isNullable()));
+                if (substitute == null) return null;
+
+                JetType fixedProjections = fixProjections(substitute);
+                if (fixedProjections == null) return null;
+
+                if (JavaPackage.getPLATFORM_TYPES() && !isSamConstructor) {
+                    return new DelegatingFlexibleType(fixedProjections, TypeUtils.makeNullable(fixedProjections));
+                }
+
+                return TypeUtils.makeNullableAsSpecified(fixedProjections, !isSamConstructor && samType.isNullable());
             }
         }
         return null;
@@ -139,7 +149,7 @@ public class SingleAbstractMethodUtils {
 
         TypeParameters typeParameters = recreateAndInitializeTypeParameters(samInterface.getTypeConstructor().getParameters(), result);
 
-        JetType parameterTypeUnsubstituted = getFunctionTypeForSamType(samInterface.getDefaultType());
+        JetType parameterTypeUnsubstituted = getFunctionTypeForSamType(samInterface.getDefaultType(), true);
         assert parameterTypeUnsubstituted != null : "couldn't get function type for SAM type " + samInterface.getDefaultType();
         JetType parameterType = typeParameters.substitutor.substitute(parameterTypeUnsubstituted, Variance.IN_VARIANCE);
         assert parameterType != null : "couldn't substitute type: " + parameterTypeUnsubstituted +
@@ -165,7 +175,7 @@ public class SingleAbstractMethodUtils {
     }
 
     public static boolean isSamType(@NotNull JetType type) {
-        return getFunctionTypeForSamType(type) != null;
+        return getFunctionTypeForSamType(type, /* irrelevant */ false) != null;
     }
 
     public static boolean isSamAdapterNecessary(@NotNull FunctionDescriptor fun) {
@@ -238,7 +248,7 @@ public class SingleAbstractMethodUtils {
         List<ValueParameterDescriptor> valueParameters = new ArrayList<ValueParameterDescriptor>(originalValueParameters.size());
         for (ValueParameterDescriptor originalParam : originalValueParameters) {
             JetType originalType = originalParam.getType();
-            JetType functionType = getFunctionTypeForSamType(originalType);
+            JetType functionType = getFunctionTypeForSamType(originalType, false);
             JetType newTypeUnsubstituted = functionType != null ? functionType : originalType;
             JetType newType = typeParameters.substitutor.substitute(newTypeUnsubstituted, Variance.IN_VARIANCE);
             assert newType != null : "couldn't substitute type: " + newTypeUnsubstituted + ", substitutor = " + typeParameters.substitutor;
diff --git a/core/descriptors/src/org/jetbrains/jet/renderer/DescriptorRendererImpl.java b/core/descriptors/src/org/jetbrains/jet/renderer/DescriptorRendererImpl.java
index 6a7a83262f4..182e6474793 100644
--- a/core/descriptors/src/org/jetbrains/jet/renderer/DescriptorRendererImpl.java
+++ b/core/descriptors/src/org/jetbrains/jet/renderer/DescriptorRendererImpl.java
@@ -292,15 +292,6 @@ public class DescriptorRendererImpl implements DescriptorRenderer {
     @NotNull
     @Override
     public String renderType(@NotNull JetType type) {
-        if (type == CANT_INFER_LAMBDA_PARAM_TYPE || type == DONT_CARE) {
-            return "???";
-        }
-        if (ErrorUtils.isUninferredParameter(type)) {
-            if (uninferredTypeParameterAsName) {
-                return renderError(((UninferredParameterTypeConstructor) type.getConstructor()).getTypeParameterDescriptor().getName().toString());
-            }
-            return "???";
-        }
         if (type instanceof FlexibleType) {
             FlexibleType flexibleType = (FlexibleType) type;
             if (!debugMode) {
@@ -310,6 +301,21 @@ public class DescriptorRendererImpl implements DescriptorRenderer {
                 return "(" + renderType(flexibleType.getLowerBound()) + ".." + renderType(flexibleType.getUpperBound()) + ")";
             }
         }
+        return renderInflexibleType(type);
+    }
+
+    private String renderInflexibleType(@NotNull JetType type) {
+        assert !TypesPackage.isFlexible(type) : "Flexible types not allowed here: " + renderType(type);
+
+        if (type == CANT_INFER_LAMBDA_PARAM_TYPE || type == DONT_CARE) {
+            return "???";
+        }
+        if (ErrorUtils.isUninferredParameter(type)) {
+            if (uninferredTypeParameterAsName) {
+                return renderError(((UninferredParameterTypeConstructor) type.getConstructor()).getTypeParameterDescriptor().getName().toString());
+            }
+            return "???";
+        }
         if (type instanceof LazyType && debugMode) {
             return type.toString();
         }
@@ -327,10 +333,14 @@ public class DescriptorRendererImpl implements DescriptorRenderer {
         JetType lower = type.getLowerBound();
         JetType upper = type.getUpperBound();
 
-        String lowerRendered = renderDefaultType(lower);
-        String upperRendered = renderDefaultType(upper);
+        String lowerRendered = renderInflexibleType(lower);
+        String upperRendered = renderInflexibleType(upper);
 
         if (differsOnlyInNullability(lowerRendered, upperRendered)) {
+            if (upperRendered.startsWith("(")) {
+                // the case of complex type, e.g. (() -> Unit)?
+                return "(" + lowerRendered + ")!";
+            }
             return lowerRendered + "!";
         }
 
@@ -358,7 +368,8 @@ public class DescriptorRendererImpl implements DescriptorRenderer {
     }
 
     private static boolean differsOnlyInNullability(String lower, String upper) {
-        return lower.equals(upper.replace("?", "")) || upper.endsWith("?") && (lower + "?").equals(upper);
+        return lower.equals(upper.replace("?", ""))
+               || upper.endsWith("?") && ((lower + "?").equals(upper)) || (("(" + lower + ")?").equals(upper));
     }
 
     @NotNull