diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
index 4a41b223c56..101767a0cc7 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java
@@ -528,6 +528,8 @@ public interface Errors {
     DiagnosticFactory1<PsiElement, InferenceErrorData> TYPE_INFERENCE_UPPER_BOUND_VIOLATED = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory2<KtElement, KotlinType, KotlinType> TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH = DiagnosticFactory2.create(ERROR);
 
+    DiagnosticFactory0<KtExpression> TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT = DiagnosticFactory0.create(ERROR, SPECIAL_CONSTRUCT_TOKEN);
+
     // Reflection
 
     DiagnosticFactory1<KtExpression, CallableMemberDescriptor> EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED = DiagnosticFactory1.create(ERROR);
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
index 6752d5416d9..148c23a2b45 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
@@ -339,6 +339,16 @@ object PositioningStrategies {
         }
     }
 
+    @JvmField val SPECIAL_CONSTRUCT_TOKEN: PositioningStrategy<KtExpression> = object : PositioningStrategy<KtExpression>() {
+        override fun mark(element: KtExpression): List<TextRange> =
+                when (element) {
+                    is KtWhenExpression -> markElement(element.whenKeyword)
+                    is KtIfExpression -> markElement(element.ifKeyword)
+                    is KtOperationExpression -> markElement(element.operationReference)
+                    else -> error("Expression is not an if, when or operation expression: ${element.getElementTextWithContext()}")
+                }
+    }
+
     @JvmField val NULLABLE_TYPE: PositioningStrategy<KtNullableType> = object : PositioningStrategy<KtNullableType>() {
         override fun mark(element: KtNullableType): List<TextRange> {
             return markNode(element.getQuestionMarkNode())
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
index 59a98edbff5..d009db238e4 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
@@ -658,6 +658,8 @@ public class DefaultErrorMessages {
         MAP.put(TYPE_INFERENCE_UPPER_BOUND_VIOLATED, "{0}", TYPE_INFERENCE_UPPER_BOUND_VIOLATED_RENDERER);
         MAP.put(TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH, "Type inference failed. Expected type mismatch: inferred type is {1} but {0} was expected", RENDER_TYPE, RENDER_TYPE);
 
+        MAP.put(TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT, "Type inference for control flow expression failed. Please specify its type explicitly.");
+
         MAP.put(WRONG_NUMBER_OF_TYPE_ARGUMENTS, "{0,choice,0#No type arguments|1#Type argument|1<{0,number,integer} type arguments} expected", (Renderer) null);
         MAP.put(NO_TYPE_ARGUMENTS_ON_RHS, "{0,choice,0#No type arguments|1#Type argument|1<{0,number,integer} type arguments} expected. " +
                                                            "Use ''{1}'' if you don''t want to pass type arguments", null, STRING);
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/ResolutionCandidate.java b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/ResolutionCandidate.java
index 1fa14694491..9f23825662e 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/ResolutionCandidate.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/ResolutionCandidate.java
@@ -51,6 +51,14 @@ public class ResolutionCandidate<D extends CallableDescriptor> {
         return new ResolutionCandidate<D>(call, descriptor, null, null, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER, null);
     }
 
+    public static <D extends CallableDescriptor> ResolutionCandidate<D> create(
+            @NotNull Call call, @NotNull D descriptor, @Nullable TypeSubstitutor knownTypeParametersResultingSubstitutor
+    ) {
+        return new ResolutionCandidate<D>(call, descriptor,
+                                          null, null, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER,
+                                          knownTypeParametersResultingSubstitutor);
+    }
+
     public static <D extends CallableDescriptor> ResolutionCandidate<D> create(
             @NotNull Call call, @NotNull D descriptor, @Nullable ReceiverValue dispatchReceiver,
             @Nullable Receiver receiverArgument, @NotNull ExplicitReceiverKind explicitReceiverKind,
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingUtils.java b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingUtils.java
index 689d56327c2..c9a793a5e29 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingUtils.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingUtils.java
@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.types.expressions;
 
+import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.intellij.lang.ASTNode;
@@ -24,6 +25,7 @@ import com.intellij.openapi.util.Ref;
 import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.descriptors.annotations.Annotations;
 import org.jetbrains.kotlin.descriptors.impl.SimpleFunctionDescriptorImpl;
@@ -50,13 +52,12 @@ import org.jetbrains.kotlin.resolve.calls.tasks.TracingStrategy;
 import org.jetbrains.kotlin.resolve.calls.util.CallMaker;
 import org.jetbrains.kotlin.resolve.descriptorUtil.AnnotationsForResolveKt;
 import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue;
-import org.jetbrains.kotlin.types.KotlinType;
-import org.jetbrains.kotlin.types.TypeUtils;
-import org.jetbrains.kotlin.types.Variance;
+import org.jetbrains.kotlin.types.*;
 import org.jetbrains.kotlin.types.typeUtil.TypeUtilsKt;
 
 import java.util.*;
 
+import static org.jetbrains.kotlin.diagnostics.Errors.TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT;
 import static org.jetbrains.kotlin.resolve.BindingContext.CALL;
 import static org.jetbrains.kotlin.resolve.BindingContext.RESOLVED_CALL;
 import static org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind.EXPECTED_TYPE_POSITION;
@@ -103,13 +104,34 @@ public class ControlStructureTypingUtils {
         SimpleFunctionDescriptorImpl function = createFunctionDescriptorForSpecialConstruction(
                 construct, argumentNames, isArgumentNullable);
         TracingStrategy tracing = createTracingForSpecialConstruction(call, construct.getName(), context);
-        ResolutionCandidate<CallableDescriptor> resolutionCandidate = ResolutionCandidate.<CallableDescriptor>create(call, function);
+        TypeSubstitutor knownTypeParameterSubstitutor = createKnownTypeParameterSubstitutorForSpecialCall(construct, function, context.expectedType);
+        ResolutionCandidate<CallableDescriptor> resolutionCandidate =
+                ResolutionCandidate.<CallableDescriptor>create(call, function, knownTypeParameterSubstitutor);
         OverloadResolutionResults<FunctionDescriptor> results = callResolver.resolveCallWithKnownCandidate(
                 call, tracing, context, resolutionCandidate, dataFlowInfoForArguments);
         assert results.isSingleResult() : "Not single result after resolving one known candidate";
         return results.getResultingCall();
     }
 
+    private static @Nullable TypeSubstitutor createKnownTypeParameterSubstitutorForSpecialCall(
+            @NotNull ResolveConstruct construct,
+            @NotNull SimpleFunctionDescriptorImpl function,
+            @NotNull KotlinType expectedType
+    ) {
+        if (construct == ResolveConstruct.ELVIS
+            || TypeUtils.noExpectedType(expectedType)
+            || TypeUtils.isDontCarePlaceholder(expectedType)
+            || KotlinBuiltIns.isUnitOrNullableUnit(expectedType)
+            || KotlinBuiltIns.isAnyOrNullableAny(expectedType)
+                ) {
+            return null;
+        }
+
+        TypeConstructor typeParameterConstructor = function.getTypeParameters().get(0).getTypeConstructor();
+        TypeProjection typeProjection = new TypeProjectionImpl(expectedType);
+        return TypeSubstitutor.create(ImmutableMap.of(typeParameterConstructor, typeProjection));
+    }
+
     private SimpleFunctionDescriptorImpl createFunctionDescriptorForSpecialConstruction(
             @NotNull ResolveConstruct construct,
             @NotNull List<String> argumentNames,
@@ -426,7 +448,15 @@ public class ControlStructureTypingUtils {
                 KtExpression expression = (KtExpression) call.getCallElement();
                 if (status.hasOnlyErrorsDerivedFrom(EXPECTED_TYPE_POSITION) || status.hasConflictingConstraints()
                         || status.hasTypeInferenceIncorporationError()) { // todo after KT-... remove this line
-                    expression.accept(checkTypeVisitor, new CheckTypeContext(context.trace, data.expectedType));
+                    if (Boolean.TRUE != expression.accept(checkTypeVisitor, new CheckTypeContext(context.trace, data.expectedType))) {
+                        KtExpression calleeExpression = call.getCalleeExpression();
+                        if (calleeExpression instanceof KtWhenExpression || calleeExpression instanceof KtIfExpression) {
+                            if (status.hasConflictingConstraints() || status.hasTypeInferenceIncorporationError()) {
+                                // TODO provide comprehensible error report for hasConflictingConstraints() case (if possible)
+                                context.trace.report(TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT.on(expression));
+                            }
+                        }
+                    }
                     return;
                 }
                 KtDeclaration parentDeclaration = PsiTreeUtil.getParentOfType(expression, KtNamedDeclaration.class);
diff --git a/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.kt b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.kt
new file mode 100644
index 00000000000..d75b6abfe43
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.kt
@@ -0,0 +1,39 @@
+// FILE: J.java
+import java.util.*;
+
+public class J {
+    public static String s = null;
+    public static Map<String, String> m = null;
+}
+
+// FILE: k.kt
+
+val testImplicitExclExcl1: String = J.s
+val testImplicitExclExcl2: String? = J.s
+
+val testImplicitExclExcl3: String = <!TYPE_MISMATCH!>J.m[""]<!>
+val testImplicitExclExcl4: String? = J.m[""]
+
+val testExclExcl1: String = J.s!!
+val testExclExcl2: String? = J.s!!
+
+val testExclExcl3: String = J.m[""]!!
+val testExclExcl4: String? = J.m[""]!!
+
+val testSafeCall1: String = <!TYPE_MISMATCH!>J.s?.let { it }<!>
+val testSafeCall2: String? = J.s?.let { it }
+
+val testSafeCall3: String = <!TYPE_MISMATCH!>J.m[""]?.let { it }<!>
+val testSafeCall4: String? = J.m[""]?.let { it.toString() }
+
+val testIf1: String = if (true) J.s else J.s
+val testIf2: String? = if (true) J.s else J.s
+
+val testIf3: String = if (true) <!TYPE_MISMATCH!>J.m[""]<!> else <!TYPE_MISMATCH!>J.m[""]<!>
+val testIf4: String? = if (true) J.m[""] else J.m[""]
+
+val testWhen1: String = when { else -> J.s }
+val testWhen2: String? = when { else -> J.s }
+
+val testWhen3: String = when { else -> <!TYPE_MISMATCH!>J.m[""]<!> }
+val testWhen4: String? = when { else -> J.m[""] }
diff --git a/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.txt b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.txt
new file mode 100644
index 00000000000..7dbb88fe86d
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.txt
@@ -0,0 +1,33 @@
+package
+
+public val testExclExcl1: kotlin.String
+public val testExclExcl2: kotlin.String?
+public val testExclExcl3: kotlin.String
+public val testExclExcl4: kotlin.String?
+public val testIf1: kotlin.String
+public val testIf2: kotlin.String?
+public val testIf3: kotlin.String
+public val testIf4: kotlin.String?
+public val testImplicitExclExcl1: kotlin.String
+public val testImplicitExclExcl2: kotlin.String?
+public val testImplicitExclExcl3: kotlin.String
+public val testImplicitExclExcl4: kotlin.String?
+public val testSafeCall1: kotlin.String
+public val testSafeCall2: kotlin.String?
+public val testSafeCall3: kotlin.String
+public val testSafeCall4: kotlin.String?
+public val testWhen1: kotlin.String
+public val testWhen2: kotlin.String?
+public val testWhen3: kotlin.String
+public val testWhen4: kotlin.String?
+
+public open class J {
+    public constructor J()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public final var m: kotlin.collections.(Mutable)Map<kotlin.String!, kotlin.String!>!
+    public final var s: kotlin.String!
+}
diff --git a/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.kt b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.kt
new file mode 100644
index 00000000000..0e8ec5e19de
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.kt
@@ -0,0 +1,20 @@
+val ns: String? = null
+
+val testElvis1: String? = ns ?: ""
+val testElvis2: String = run { ns ?: "" }
+val testElvis3: String? = run { ns ?: "" }
+
+val testIf1: String? = if (true) "" else ""
+val testIf2: String? = run { if (true) "" else "" }
+val testIf3: String? = if (true) run { "" } else ""
+val testIf4: String? = run { run { if (true) "" else "" } }
+val testIf5: String? = run { if (true) run { "" } else "" }
+
+val testWhen1: String? = when { else -> "" }
+val testWhen2: String? = run { when { else -> "" } }
+val testWhen3: String? = when { else -> run { "" } }
+val testWhen4: String? = run { run { when { else -> "" } } }
+val testWhen5: String? = run { when { else -> run { "" } } }
+
+val testExcl1: String? = run { ns!! }
+val testExcl2: String? = run { run { ns!! } }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.txt b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.txt
new file mode 100644
index 00000000000..6c9aadb9727
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.txt
@@ -0,0 +1,18 @@
+package
+
+public val ns: kotlin.String? = null
+public val testElvis1: kotlin.String?
+public val testElvis2: kotlin.String
+public val testElvis3: kotlin.String?
+public val testExcl1: kotlin.String?
+public val testExcl2: kotlin.String?
+public val testIf1: kotlin.String?
+public val testIf2: kotlin.String?
+public val testIf3: kotlin.String?
+public val testIf4: kotlin.String?
+public val testIf5: kotlin.String?
+public val testWhen1: kotlin.String?
+public val testWhen2: kotlin.String?
+public val testWhen3: kotlin.String?
+public val testWhen4: kotlin.String?
+public val testWhen5: kotlin.String?
diff --git a/compiler/testData/diagnostics/tests/infos/SmartCasts.kt b/compiler/testData/diagnostics/tests/infos/SmartCasts.kt
index c38d54c7aef..3c036401686 100644
--- a/compiler/testData/diagnostics/tests/infos/SmartCasts.kt
+++ b/compiler/testData/diagnostics/tests/infos/SmartCasts.kt
@@ -181,8 +181,8 @@ fun returnFunctionLiteral(a: Any?): Function0<Int> {
     else return { -> 1 }
 }
 
-fun returnFunctionLiteralDoesntWork(a: Any?): Function0<Int> =
-        if (a is Int) <!TYPE_MISMATCH!>{ -> a }<!>
+fun returnFunctionLiteralExpressionBody(a: Any?): Function0<Int> =
+        if (a is Int) { -> <!DEBUG_INFO_SMARTCAST!>a<!> }
         else { -> 1 }
 
 
diff --git a/compiler/testData/diagnostics/tests/infos/SmartCasts.txt b/compiler/testData/diagnostics/tests/infos/SmartCasts.txt
index 6abe1150e98..96fb52a7a75 100644
--- a/compiler/testData/diagnostics/tests/infos/SmartCasts.txt
+++ b/compiler/testData/diagnostics/tests/infos/SmartCasts.txt
@@ -17,7 +17,7 @@ public fun illegalWhenBody(/*0*/ a: kotlin.Any): kotlin.Int
 public fun mergeSmartCasts(/*0*/ a: kotlin.Any?): kotlin.Unit
 public fun returnFunctionLiteral(/*0*/ a: kotlin.Any?): () -> kotlin.Int
 public fun returnFunctionLiteralBlock(/*0*/ a: kotlin.Any?): () -> kotlin.Int
-public fun returnFunctionLiteralDoesntWork(/*0*/ a: kotlin.Any?): () -> kotlin.Int
+public fun returnFunctionLiteralExpressionBody(/*0*/ a: kotlin.Any?): () -> kotlin.Int
 public fun toInt(/*0*/ i: kotlin.Int?): kotlin.Int
 public fun vars(/*0*/ a: kotlin.Any?): kotlin.Unit
 
diff --git a/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.kt b/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.kt
index 1764d1da8d0..7433a8cdb7c 100644
--- a/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.kt
+++ b/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.kt
@@ -8,9 +8,21 @@ interface D: A, B
 interface E: A, B
 
 fun foo(c: C?, d: D?, e: E?) {
-    val a: A? = <!TYPE_MISMATCH!>c ?: d<!> ?: e
+    val test1: A? = <!TYPE_MISMATCH!>c ?: d<!> ?: e
 
-    val b: B? = if (false) <!TYPE_MISMATCH!>if (true) c else d<!> else e
+    val test2: B? = if (false) if (true) c else d else e
 
-    //outer elvis operator and if-expression have error types
+    val test3: A? = when {
+        true -> c
+        else -> when {
+            true -> d
+            else -> e
+        }
+    }
+
+    val test4: B? = when (1) {
+        1 -> c
+        2 -> d
+        else -> e
+    }
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/when/kt10809.kt b/compiler/testData/diagnostics/tests/when/kt10809.kt
new file mode 100644
index 00000000000..e04ff8feb23
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/kt10809.kt
@@ -0,0 +1,50 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -DEBUG_INFO_SMARTCAST
+
+interface Data
+interface Item
+class FlagData(val value: Boolean) : Data
+class ListData<T : Item>(val list: List<T>) : Data
+
+fun <T> listOf(vararg items: T): List<T> = null!!
+
+fun test1(o: Any) = <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT!>when<!> (o) {
+    is List<*> ->
+        ListData(listOf())
+    is Int -> when {
+        o < 0 ->
+            FlagData(true)
+        else ->
+            null
+    }
+    else ->
+        null
+}
+
+fun test1x(o: Any): Data? = when (o) {
+    is List<*> ->
+        ListData(listOf())
+    is Int -> when {
+        o < 0 ->
+            FlagData(true)
+        else ->
+            null
+    }
+    else ->
+        null
+}
+
+fun test2() =
+        <!TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT!>if<!> (true)
+            ListData(listOf())
+        else
+            FlagData(true)
+
+fun test2x(): Data =
+        if (true) ListData(listOf()) else FlagData(true)
+
+fun test2y(): Any =
+        if (true) ListData(listOf()) else FlagData(true)
+
+fun test2z(): Any =
+        run { if (true) ListData(listOf()) else FlagData(true) }
+
diff --git a/compiler/testData/diagnostics/tests/when/kt10809.txt b/compiler/testData/diagnostics/tests/when/kt10809.txt
new file mode 100644
index 00000000000..f1a2f161ff5
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/kt10809.txt
@@ -0,0 +1,37 @@
+package
+
+public fun </*0*/ T> listOf(/*0*/ vararg items: T /*kotlin.Array<out T>*/): kotlin.collections.List<T>
+public fun test1(/*0*/ o: kotlin.Any): ???
+public fun test1x(/*0*/ o: kotlin.Any): Data?
+public fun test2(): ???
+public fun test2x(): Data
+public fun test2y(): kotlin.Any
+public fun test2z(): kotlin.Any
+
+public interface Data {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class FlagData : Data {
+    public constructor FlagData(/*0*/ value: kotlin.Boolean)
+    public final val value: kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Item {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class ListData</*0*/ T : Item> : Data {
+    public constructor ListData</*0*/ T : Item>(/*0*/ list: kotlin.collections.List<T>)
+    public final val list: kotlin.collections.List<T>
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/when/kt10811.kt b/compiler/testData/diagnostics/tests/when/kt10811.kt
new file mode 100644
index 00000000000..e99415e09a4
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/kt10811.kt
@@ -0,0 +1,24 @@
+interface Maybe<T>
+class Some<T>(val value: T) : Maybe<T>
+class None<T> : Maybe<T>
+
+fun <T> none() : None<T> = TODO()
+
+fun test1() : Maybe<String?> = if (true) none() else Some("")
+
+fun test2() : Maybe<String?> = when {
+    true -> none()
+    else -> Some("")
+}
+
+fun test3() : Maybe<String?> = when {
+    true -> none()
+    else -> Some<String?>("")
+}
+
+fun test4() : Maybe<String?> {
+    when ("") {
+        "a" -> return none()
+        else -> return Some<String?>("")
+    }
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/when/kt10811.txt b/compiler/testData/diagnostics/tests/when/kt10811.txt
new file mode 100644
index 00000000000..1e85562d5c1
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/kt10811.txt
@@ -0,0 +1,28 @@
+package
+
+public fun </*0*/ T> none(): None<T>
+public fun test1(): Maybe<kotlin.String?>
+public fun test2(): Maybe<kotlin.String?>
+public fun test3(): Maybe<kotlin.String?>
+public fun test4(): Maybe<kotlin.String?>
+
+public interface Maybe</*0*/ T> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class None</*0*/ T> : Maybe<T> {
+    public constructor None</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Some</*0*/ T> : Maybe<T> {
+    public constructor Some</*0*/ T>(/*0*/ value: T)
+    public final val value: T
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt b/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt
new file mode 100644
index 00000000000..b899b3edb98
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt
@@ -0,0 +1,24 @@
+val test1: (String) -> Boolean =
+        when {
+            true -> {{ true }}
+            else -> {{ false }}
+        }
+
+val test2: (String) -> Boolean =
+        when {
+            true -> {{ true }}
+            else -> null!!
+        }
+
+val test3: (String) -> Boolean =
+        when {
+            true -> { s -> true }
+            else -> null!!
+        }
+
+val test4: (String) -> Boolean =
+        when {
+            true -> { <!EXPECTED_PARAMETERS_NUMBER_MISMATCH!>s1, <!CANNOT_INFER_PARAMETER_TYPE!>s2<!><!> -> true }
+            else -> null!!
+        }
+
diff --git a/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.txt b/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.txt
new file mode 100644
index 00000000000..9cba7226978
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.txt
@@ -0,0 +1,6 @@
+package
+
+public val test1: (kotlin.String) -> kotlin.Boolean
+public val test2: (kotlin.String) -> kotlin.Boolean
+public val test3: (kotlin.String) -> kotlin.Boolean
+public val test4: (kotlin.String) -> kotlin.Boolean
diff --git a/compiler/testData/diagnostics/testsWithStdLib/kt10192.kt b/compiler/testData/diagnostics/testsWithStdLib/when/kt10192.kt
similarity index 100%
rename from compiler/testData/diagnostics/testsWithStdLib/kt10192.kt
rename to compiler/testData/diagnostics/testsWithStdLib/when/kt10192.kt
diff --git a/compiler/testData/diagnostics/testsWithStdLib/kt10192.txt b/compiler/testData/diagnostics/testsWithStdLib/when/kt10192.txt
similarity index 100%
rename from compiler/testData/diagnostics/testsWithStdLib/kt10192.txt
rename to compiler/testData/diagnostics/testsWithStdLib/when/kt10192.txt
diff --git a/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt b/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt
new file mode 100644
index 00000000000..6d8c7badb00
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt
@@ -0,0 +1,17 @@
+import java.util.*
+import kotlin.comparisons.compareBy
+import kotlin.comparisons.nullsLast
+
+class Foo(val a: String, val b: Int)
+
+fun getComp(): Comparator<Foo?> =
+        when {
+            else -> nullsLast(compareBy({ it.a }, { it.b }))
+        }
+
+fun getCompInverted(): Comparator<Foo?> =
+        nullsLast(
+                when {
+                    else -> compareBy({ it.a }, { it.b })
+                }
+        )
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.txt b/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.txt
new file mode 100644
index 00000000000..b3a68964599
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/when/kt10807.txt
@@ -0,0 +1,13 @@
+package
+
+public fun getComp(): java.util.Comparator<Foo?>
+public fun getCompInverted(): java.util.Comparator<Foo?>
+
+public final class Foo {
+    public constructor Foo(/*0*/ a: kotlin.String, /*1*/ b: kotlin.Int)
+    public final val a: kotlin.String
+    public final val b: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.kt b/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.kt
new file mode 100644
index 00000000000..b61e8987e4a
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.kt
@@ -0,0 +1,41 @@
+import java.util.*
+
+fun <T> nullable(x: T): T? = x
+
+@Suppress("UNUSED_PARAMETER")
+fun <T> select(x1: T, x2: T): T = x1
+
+val test1 =
+        listOf(1, 2, 3).mapNotNullTo(ArrayList()) {
+            if (true) nullable(it) else null
+        }
+
+val test2: MutableList<Int?> =
+        listOf(1, 2, 3).mapNotNullTo(ArrayList()) {
+            if (true) nullable(it) else null
+        }
+
+val test3: MutableList<Int> =
+        listOf(1, 2, 3).mapNotNullTo(ArrayList()) {
+            if (true) nullable(it) else null
+        }
+
+val test4: Collection<Int> =
+        listOf(1, 2, 3).flatMapTo(LinkedHashSet()) {
+            listOf(it)
+        }
+
+val test5: Collection<Int> =
+        listOf(1, 2, 3).<!TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH!>flatMapTo(<!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>LinkedHashSet<!>()) { // TODO
+            if (true) listOf(it) else listOf(it)
+        }<!>
+
+val test6: Collection<Int> =
+        listOf(1, 2, 3).flatMapTo(LinkedHashSet<Int>()) {
+            if (true) listOf(it) else listOf(it)
+        }
+
+val test7: Collection<Int> =
+        listOf(1, 2, 3).flatMapTo(LinkedHashSet()) {
+            select(listOf(it), listOf(it))
+        }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.txt b/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.txt
new file mode 100644
index 00000000000..d3bb98a173d
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.txt
@@ -0,0 +1,11 @@
+package
+
+public val test1: java.util.ArrayList<kotlin.Int>
+public val test2: kotlin.collections.MutableList<kotlin.Int?>
+public val test3: kotlin.collections.MutableList<kotlin.Int>
+public val test4: kotlin.collections.Collection<kotlin.Int>
+public val test5: kotlin.collections.Collection<kotlin.Int>
+public val test6: kotlin.collections.Collection<kotlin.Int>
+public val test7: kotlin.collections.Collection<kotlin.Int>
+public fun </*0*/ T> nullable(/*0*/ x: T): T?
+@kotlin.Suppress(names = {"UNUSED_PARAMETER"}) public fun </*0*/ T> select(/*0*/ x1: T, /*1*/ x2: T): T
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
index 2b543abc095..d3253f39674 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
@@ -3438,6 +3438,18 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("specialConstructsAndPlatformTypes.kt")
+            public void testSpecialConstructsAndPlatformTypes() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/controlStructures/specialConstructsAndPlatformTypes.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("specialConstructsWithNullableExpectedType.kt")
+            public void testSpecialConstructsWithNullableExpectedType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/controlStructures/specialConstructsWithNullableExpectedType.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("tryReturnType.kt")
             public void testTryReturnType() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/controlStructures/tryReturnType.kt");
@@ -18714,6 +18726,18 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("kt10809.kt")
+            public void testKt10809() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/kt10809.kt");
+                doTest(fileName);
+            }
+
+            @TestMetadata("kt10811.kt")
+            public void testKt10811() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/kt10811.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("kt4434.kt")
             public void testKt4434() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/kt4434.kt");
@@ -18834,6 +18858,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("whenAndLambdaWithExpectedType.kt")
+            public void testWhenAndLambdaWithExpectedType() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/whenAndLambdaWithExpectedType.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("WhenTypeDisjunctions.kt")
             public void testWhenTypeDisjunctions() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/when/WhenTypeDisjunctions.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
index 53e901efb72..10868f7c5c1 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
@@ -95,12 +95,6 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
         doTest(fileName);
     }
 
-    @TestMetadata("kt10192.kt")
-    public void testKt10192() throws Exception {
-        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/kt10192.kt");
-        doTest(fileName);
-    }
-
     @TestMetadata("kt9078.kt")
     public void testKt9078() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/kt9078.kt");
@@ -1207,4 +1201,31 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
             doTest(fileName);
         }
     }
+
+    @TestMetadata("compiler/testData/diagnostics/testsWithStdLib/when")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class When extends AbstractDiagnosticsTestWithStdLib {
+        public void testAllFilesPresentInWhen() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/testsWithStdLib/when"), Pattern.compile("^(.+)\\.kt$"), true);
+        }
+
+        @TestMetadata("kt10192.kt")
+        public void testKt10192() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/when/kt10192.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("kt10807.kt")
+        public void testKt10807() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("noTypeArgumentsInConstructor.kt")
+        public void testNoTypeArgumentsInConstructor() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithStdLib/when/noTypeArgumentsInConstructor.kt");
+            doTest(fileName);
+        }
+    }
 }
diff --git a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
index 1b701cfc6eb..0e8afaa0642 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
+++ b/core/descriptors/src/org/jetbrains/kotlin/builtins/KotlinBuiltIns.java
@@ -1097,6 +1097,10 @@ public abstract class KotlinBuiltIns {
         return isNotNullConstructedFromGivenClass(type, FQ_NAMES.unit);
     }
 
+    public static boolean isUnitOrNullableUnit(@NotNull KotlinType type) {
+        return isConstructedFromGivenClass(type, FQ_NAMES.unit);
+    }
+
     public boolean isBooleanOrSubtype(@NotNull KotlinType type) {
         return KotlinTypeChecker.DEFAULT.isSubtypeOf(type, getBooleanType());
     }
diff --git a/idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt b/idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt
index dec74dd8e1d..5209f34de0b 100644
--- a/idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt
+++ b/idea/ide-common/src/org/jetbrains/kotlin/idea/codeInsight/ReferenceVariantsHelper.kt
@@ -197,7 +197,7 @@ class ReferenceVariantsHelper(
         }
 
         if (callType == CallType.SUPER_MEMBERS) { // we need to unwrap fake overrides in case of "super." because ShadowedDeclarationsFilter does not work correctly
-            return descriptors.flatMapTo(LinkedHashSet()) {
+            return descriptors.flatMapTo(LinkedHashSet<DeclarationDescriptor>()) {
                 if (it is CallableMemberDescriptor && it.kind == CallableMemberDescriptor.Kind.FAKE_OVERRIDE) it.overriddenDescriptors else listOf(it)
             }
         }