KT-1875 Safe call should be binded with receiver or this object (but not with both by default)

#KT-1875 fixed

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/CallResolver.java

@@ -224,6 +224,7 @@ public class CallResolver {
                 FunctionDescriptorUtil.initializeFromFunctionType(functionDescriptor, calleeType, NO_RECEIVER);
                 ResolutionCandidate<CallableDescriptor> resolutionCandidate = ResolutionCandidate.<CallableDescriptor>create(functionDescriptor);
                 resolutionCandidate.setReceiverArgument(context.call.getExplicitReceiver());
+                resolutionCandidate.setExplicitReceiverKind(ExplicitReceiverKind.RECEIVER_ARGUMENT);
 
                 // strictly speaking, this is a hack:
                 // we need to pass a reference, but there's no reference in the PSI,
@@ -327,7 +328,7 @@ public class CallResolver {
             // Now, we try to remove this argument and see if it helps
             Collection<ResolutionCandidate<D>> newCandidates = Lists.newArrayList();
             for (ResolutionCandidate<D> candidate : task.getCandidates()) {
-                newCandidates.add(ResolutionCandidate.create(candidate.getDescriptor()));
+                newCandidates.add(ResolutionCandidate.create(candidate.getDescriptor(), candidate.getExplicitReceiverKind()));
             }
             ResolutionTask<D, F> newContext = new ResolutionTask<D, F>(newCandidates, task.reference, TemporaryBindingTrace.create(task.trace), task.scope, new DelegatingCall(task.call) {
                             @NotNull
@@ -628,20 +629,35 @@ public class CallResolver {
     private <D extends CallableDescriptor, F extends D> ResolutionStatus checkAllValueArguments(CallResolutionContext<D, F> context) {
         ResolutionStatus result = checkValueArgumentTypes(context);
         ResolvedCall candidateCall = context.candidateCall;
-        result = result.combine(checkReceiver(context, candidateCall.getResultingDescriptor().getReceiverParameter(), candidateCall.getReceiverArgument()));
-        result = result.combine(checkReceiver(context, candidateCall.getResultingDescriptor().getExpectedThisObject(), candidateCall.getThisObject()));
+
+        // Comment about a very special case.
+        // Call 'b.foo(1)' where class 'Foo' has an extension member 'fun B.invoke(Int)' should be checked two times for safe call (in 'checkReceiver'), because
+        // both 'b' (receiver) and 'foo' (this object) might be nullable. In the first case we mark dot, in the second 'foo'.
+        // Class 'CallForImplicitInvoke' helps up to recognise this case, and parameter 'implicitInvokeCheck' helps us to distinguish whether we check receiver or this object.
+
+        result = result.combine(checkReceiver(context, candidateCall.getResultingDescriptor().getReceiverParameter(), candidateCall.getReceiverArgument(),
+                                              candidateCall.getExplicitReceiverKind().isReceiver(), false));
+
+        result = result.combine(checkReceiver(context, candidateCall.getResultingDescriptor().getExpectedThisObject(), candidateCall.getThisObject(),
+                                              candidateCall.getExplicitReceiverKind().isThisObject(),
+                                              // for the invocation 'foo(1)' where foo is a variable of function type we should mark 'foo' as callOperationNode if necessary
+                                              context.call instanceof CallTransformer.CallForImplicitInvoke));
         return result;
     }
 
-    private <D extends CallableDescriptor, F extends D> ResolutionStatus checkReceiver(CallResolutionContext<D, F> context, ReceiverDescriptor receiverParameter, ReceiverDescriptor receiverArgument) {
+    private <D extends CallableDescriptor, F extends D> ResolutionStatus checkReceiver(CallResolutionContext<D, F> context, ReceiverDescriptor receiverParameter, ReceiverDescriptor receiverArgument,
+            boolean isExplicitReceiver, boolean implicitInvokeCheck) {
+
         ResolutionStatus result = SUCCESS;
         if (receiverParameter.exists() && receiverArgument.exists()) {
             ASTNode callOperationNode = context.call.getCallOperationNode();
-            boolean safeAccess = callOperationNode != null && callOperationNode.getElementType() == JetTokens.SAFE_ACCESS;
+
+            boolean safeAccess = !implicitInvokeCheck && isExplicitReceiver && callOperationNode != null && callOperationNode.getElementType() == JetTokens.SAFE_ACCESS;
             JetType receiverArgumentType = receiverArgument.getType();
             AutoCastServiceImpl autoCastService = new AutoCastServiceImpl(context.dataFlowInfo, context.candidateCall.getTrace().getBindingContext());
             if (!safeAccess && !receiverParameter.getType().isNullable() && !autoCastService.isNotNull(receiverArgument)) {
-                context.tracing.unsafeCall(context.candidateCall.getTrace(), receiverArgumentType);
+
+                context.tracing.unsafeCall(context.candidateCall.getTrace(), receiverArgumentType, implicitInvokeCheck);
                 result = UNSAFE_CALL_ERROR;
             }
             else {
@@ -653,7 +669,6 @@ public class CallResolver {
                     result = OTHER_ERROR;
                 }
             }
-
             if (safeAccess && (receiverParameter.getType().isNullable() || !receiverArgumentType.isNullable())) {
                 context.tracing.unnecessarySafeCall(context.candidateCall.getTrace(), receiverArgumentType);
             }
@@ -840,9 +855,6 @@ public class CallResolver {
             TemporaryBindingTrace temporaryTrace = result.getTrace();
             temporaryTrace.commit();
 
-            if (result instanceof VariableAsFunctionResolvedCall) {
-                ((VariableAsFunctionResolvedCall)result).getVariableCall().getTrace().commit();
-            }
             return OverloadResolutionResultsImpl.success(result);
         }
     }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/CallTransformer.java

@@ -101,7 +101,7 @@ public class CallTransformer<D extends CallableDescriptor, F extends D> {
                     candidate, variableCall, temporaryTrace, task);
 
             ResolutionCandidate<CallableDescriptor> candidateWithoutReceiver = ResolutionCandidate.create(
-                    candidate.getDescriptor(), candidate.getThisObject(), ReceiverDescriptor.NO_RECEIVER);
+                    candidate.getDescriptor(), candidate.getThisObject(), ReceiverDescriptor.NO_RECEIVER, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER);
 
             CallResolutionContext<CallableDescriptor, FunctionDescriptor> contextWithoutReceiver = createContextWithChainedTrace(
                     candidateWithoutReceiver, variableCallWithoutReceiver, temporaryTrace, task);
@@ -203,7 +203,7 @@ public class CallTransformer<D extends CallableDescriptor, F extends D> {
             final JetSimpleNameExpression invokeExpression = (JetSimpleNameExpression) JetPsiFactory.createExpression(
                     task.call.getCallElement().getProject(), "invoke");
 
-            return new DelegatingCall(task.call) {
+            return new CallForImplicitInvoke(task.call) {
                 @NotNull
                 @Override
                 public ReceiverDescriptor getExplicitReceiver() {
@@ -236,4 +236,10 @@ public class CallTransformer<D extends CallableDescriptor, F extends D> {
             };
         }
     };
+
+    public static class CallForImplicitInvoke extends DelegatingCall {
+        public CallForImplicitInvoke(@NotNull Call delegate) {
+            super(delegate);
+        }
+    }
 }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/ExplicitReceiverKind.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2010-2012 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.resolve.calls;
+
+/**
+ * @author svtk
+ */
+public enum ExplicitReceiverKind {
+    RECEIVER_ARGUMENT,
+    THIS_OBJECT,
+    NO_EXPLICIT_RECEIVER,
+
+    // A very special case.
+    // In a call 'b.foo(1)' where class 'Foo' has an extension member 'fun B.invoke(Int)' function 'invoke' has two explicit receivers:
+    // 'b' (as receiver argument) and 'foo' (as this object).
+    BOTH_RECEIVERS;
+
+    public boolean isReceiver() {
+        return this == RECEIVER_ARGUMENT || this == BOTH_RECEIVERS;
+    }
+
+    public boolean isThisObject() {
+        return this == THIS_OBJECT || this == BOTH_RECEIVERS;
+    }
+}

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/ResolutionCandidate.java

@@ -33,6 +33,7 @@ public class ResolutionCandidate<D extends CallableDescriptor> {
     private final D candidateDescriptor;
     private ReceiverDescriptor thisObject; // receiver object of a method
     private ReceiverDescriptor receiverArgument; // receiver of an extension function
+    private ExplicitReceiverKind explicitReceiverKind;
 
     private ResolutionCandidate(@NotNull D descriptor, @NotNull ReceiverDescriptor thisObject, @NotNull ReceiverDescriptor receiverArgument) {
         this.candidateDescriptor = descriptor;
@@ -44,8 +45,16 @@ public class ResolutionCandidate<D extends CallableDescriptor> {
         return new ResolutionCandidate<D>(descriptor, NO_RECEIVER, NO_RECEIVER);
     }
 
-    public static <D extends CallableDescriptor> ResolutionCandidate<D> create(@NotNull D descriptor, @NotNull ReceiverDescriptor thisObject, @NotNull ReceiverDescriptor receiverArgument) {
-        return new ResolutionCandidate<D>(descriptor, thisObject, receiverArgument);
+    public static <D extends CallableDescriptor> ResolutionCandidate<D> create(@NotNull D descriptor, @NotNull ExplicitReceiverKind explicitReceiverKind) {
+        ResolutionCandidate<D> candidate = new ResolutionCandidate<D>(descriptor, NO_RECEIVER, NO_RECEIVER);
+        candidate.setExplicitReceiverKind(explicitReceiverKind);
+        return candidate;
+    }
+
+    public static <D extends CallableDescriptor> ResolutionCandidate<D> create(@NotNull D descriptor, @NotNull ReceiverDescriptor thisObject, @NotNull ReceiverDescriptor receiverArgument, @NotNull ExplicitReceiverKind explicitReceiverKind) {
+        ResolutionCandidate<D> resolutionCandidate = new ResolutionCandidate<D>(descriptor, thisObject, receiverArgument);
+        resolutionCandidate.setExplicitReceiverKind(explicitReceiverKind);
+        return resolutionCandidate;
     }
 
     public void setThisObject(@NotNull ReceiverDescriptor thisObject) {
@@ -56,6 +65,10 @@ public class ResolutionCandidate<D extends CallableDescriptor> {
         this.receiverArgument = receiverArgument;
     }
 
+    public void setExplicitReceiverKind(@NotNull ExplicitReceiverKind explicitReceiverKind) {
+        this.explicitReceiverKind = explicitReceiverKind;
+    }
+
     @NotNull
     public D getDescriptor() {
         return candidateDescriptor;
@@ -70,12 +83,19 @@ public class ResolutionCandidate<D extends CallableDescriptor> {
     public ReceiverDescriptor getReceiverArgument() {
         return receiverArgument;
     }
-    
+
+    @NotNull
+    public ExplicitReceiverKind getExplicitReceiverKind() {
+        return explicitReceiverKind;
+    }
+
     @NotNull
     public static <D extends CallableDescriptor> List<ResolutionCandidate<D>> convertCollection(@NotNull Collection<? extends D> descriptors) {
         List<ResolutionCandidate<D>> result = Lists.newArrayList();
         for (D descriptor : descriptors) {
-            result.add(create(descriptor));
+            ResolutionCandidate<D> candidate = create(descriptor);
+            candidate.setExplicitReceiverKind(ExplicitReceiverKind.NO_EXPLICIT_RECEIVER);
+            result.add(candidate);
         }
         return result;
     }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/ResolutionTask.java

@@ -16,7 +16,6 @@
 
 package org.jetbrains.jet.lang.resolve.calls;
 
-import com.google.common.collect.Multimap;
 import com.google.common.collect.Sets;
 import com.intellij.lang.ASTNode;
 import com.intellij.psi.PsiElement;
@@ -195,9 +194,9 @@ public class ResolutionTask<D extends CallableDescriptor, F extends D> extends R
         }
 
         @Override
-        public void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type) {
+        public void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type, boolean isCallForImplicitInvoke) {
             ASTNode callOperationNode = call.getCallOperationNode();
-            if (callOperationNode != null) {
+            if (callOperationNode != null && !isCallForImplicitInvoke) {
                 trace.report(UNSAFE_CALL.on(callOperationNode.getPsi(), type));
             }
             else {

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/ResolvedCall.java

@@ -46,6 +46,10 @@ public interface ResolvedCall<D extends CallableDescriptor> {
     @NotNull
     ReceiverDescriptor getThisObject();
 
+    /** Determines whether receiver argument or this object is substituted for explicit receiver */
+    @NotNull
+    ExplicitReceiverKind getExplicitReceiverKind();
+
     /** Values (arguments) for value parameters */
     @NotNull
     Map<ValueParameterDescriptor, ResolvedValueArgument> getValueArguments();

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/ResolvedCallImpl.java

@@ -53,18 +53,14 @@ public class ResolvedCallImpl<D extends CallableDescriptor> implements ResolvedC
 
     @NotNull
     public static <D extends CallableDescriptor> ResolvedCallImpl<D> create(@NotNull ResolutionCandidate<D> candidate, @NotNull TemporaryBindingTrace trace) {
-        return create(candidate.getDescriptor(), candidate.getThisObject(), candidate.getReceiverArgument(), trace);
-    }
-
-    @NotNull
-    public static <D extends CallableDescriptor> ResolvedCallImpl<D> create(@NotNull D descriptor, @NotNull ReceiverDescriptor thisObject, @NotNull ReceiverDescriptor receiverArgument, @NotNull TemporaryBindingTrace trace) {
-        return new ResolvedCallImpl<D>(descriptor, thisObject, receiverArgument, trace);
+        return new ResolvedCallImpl<D>(candidate, trace);
     }
 
     private final D candidateDescriptor;
     private D resultingDescriptor; // Probably substituted
     private final ReceiverDescriptor thisObject; // receiver object of a method
     private final ReceiverDescriptor receiverArgument; // receiver of an extension function
+    private final ExplicitReceiverKind explicitReceiverKind;
 
     private final Map<TypeParameterDescriptor, JetType> typeArguments = Maps.newLinkedHashMap();
     private final Map<ValueParameterDescriptor, JetType> autoCasts = Maps.newHashMap();
@@ -73,13 +69,15 @@ public class ResolvedCallImpl<D extends CallableDescriptor> implements ResolvedC
     private TemporaryBindingTrace trace;
     private ResolutionStatus status = UNKNOWN_STATUS;
 
-    private ResolvedCallImpl(@NotNull D candidateDescriptor, @NotNull ReceiverDescriptor thisObject, @NotNull ReceiverDescriptor receiverArgument, @NotNull TemporaryBindingTrace trace) {
-        this.candidateDescriptor = candidateDescriptor;
-        this.thisObject = thisObject;
-        this.receiverArgument = receiverArgument;
+    private ResolvedCallImpl(@NotNull ResolutionCandidate<D> candidate, @NotNull TemporaryBindingTrace trace) {
+        this.candidateDescriptor = candidate.getDescriptor();
+        this.thisObject = candidate.getThisObject();
+        this.receiverArgument = candidate.getReceiverArgument();
+        this.explicitReceiverKind = candidate.getExplicitReceiverKind();
         this.trace = trace;
     }
 
+    @Override
     @NotNull
     public ResolutionStatus getStatus() {
         return status;
@@ -89,6 +87,7 @@ public class ResolvedCallImpl<D extends CallableDescriptor> implements ResolvedC
         this.status = this.status.combine(status);
     }
 
+    @Override
     @NotNull
     public TemporaryBindingTrace getTrace() {
         return trace;
@@ -138,6 +137,12 @@ public class ResolvedCallImpl<D extends CallableDescriptor> implements ResolvedC
         return thisObject;
     }
 
+    @Override
+    @NotNull
+    public ExplicitReceiverKind getExplicitReceiverKind() {
+        return explicitReceiverKind;
+    }
+
     @Override
     @NotNull
     public Map<ValueParameterDescriptor, ResolvedValueArgument> getValueArguments() {
@@ -171,6 +176,7 @@ public class ResolvedCallImpl<D extends CallableDescriptor> implements ResolvedC
         this.someArgumentHasNoType = true;
     }
 
+    @Override
     public boolean isDirty() {
         return someArgumentHasNoType;
     }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/TaskPrioritizer.java

@@ -109,7 +109,8 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
         AutoCastServiceImpl autoCastService = new AutoCastServiceImpl(context.dataFlowInfo, context.trace.getBindingContext());
         List<ReceiverDescriptor> implicitReceivers = Lists.newArrayList();
         scope.getImplicitReceiversHierarchy(implicitReceivers);
-        if (context.call.getThisObject().exists()) {
+        boolean hasExplicitThisObject = context.call.getThisObject().exists();
+        if (hasExplicitThisObject) {
             implicitReceivers.add(context.call.getThisObject());
         }
         if (receiver.exists()) {
@@ -124,7 +125,7 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
             Collection<ResolutionCandidate<D>> members = Lists.newArrayList();
             for (ReceiverDescriptor variant : variantsForExplicitReceiver) {
                 Collection<? extends D> membersForThisVariant = callableDescriptorCollector.getMembersByName(variant.getType(), name);
-                convertWithReceivers(membersForThisVariant, Collections.singletonList(variant), Collections.singletonList(NO_RECEIVER), members);
+                convertWithReceivers(membersForThisVariant, Collections.singletonList(variant), Collections.singletonList(NO_RECEIVER), members, hasExplicitThisObject);
             }
 
             result.addLocalExtensions(locals);
@@ -134,7 +135,7 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
                 Collection<? extends D> memberExtensions = callableDescriptorCollector.getNonMembersByName(
                         implicitReceiver.getType().getMemberScope(), name);
                 List<ReceiverDescriptor> variantsForImplicitReceiver = autoCastService.getVariantsForReceiver(implicitReceiver);
-                result.addNonLocalExtensions(convertWithReceivers(memberExtensions, variantsForImplicitReceiver, variantsForExplicitReceiver));
+                result.addNonLocalExtensions(convertWithReceivers(memberExtensions, variantsForImplicitReceiver, variantsForExplicitReceiver, hasExplicitThisObject));
             }
 
             result.addNonLocalExtensions(nonlocals);
@@ -157,20 +158,26 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
         }
     }
 
-    private static <D extends CallableDescriptor> Collection<ResolutionCandidate<D>> convertWithReceivers(Collection<? extends D> descriptors, Iterable<ReceiverDescriptor> thisObjects, Iterable<ReceiverDescriptor> receiverParameters) {
+    private static <D extends CallableDescriptor> Collection<ResolutionCandidate<D>> convertWithReceivers(Collection<? extends D> descriptors, Iterable<ReceiverDescriptor> thisObjects,
+            Iterable<ReceiverDescriptor> receiverParameters, boolean hasExplicitThisObject) {
+
         Collection<ResolutionCandidate<D>> result = Lists.newArrayList();
-        convertWithReceivers(descriptors, thisObjects, receiverParameters, result);
+        convertWithReceivers(descriptors, thisObjects, receiverParameters, result, hasExplicitThisObject);
         return result;
     }
 
-    private static <D extends CallableDescriptor> void convertWithReceivers(Collection<? extends D> descriptors, Iterable<ReceiverDescriptor> thisObjects, Iterable<ReceiverDescriptor> receiverParameters, Collection<ResolutionCandidate<D>> result) {
+    private static <D extends CallableDescriptor> void convertWithReceivers(Collection<? extends D> descriptors, Iterable<ReceiverDescriptor> thisObjects, Iterable<ReceiverDescriptor> receiverParameters,
+            Collection<ResolutionCandidate<D>> result, boolean hasExplicitThisObject) {
+
         for (ReceiverDescriptor thisObject : thisObjects) {
             for (ReceiverDescriptor receiverParameter : receiverParameters) {
                 for (D extension : descriptors) {
-                    ResolutionCandidate<D> resolvedCall = ResolutionCandidate.create(extension);
-                    resolvedCall.setThisObject(thisObject);
-                    resolvedCall.setReceiverArgument(receiverParameter);
-                    result.add(resolvedCall);
+                    ResolutionCandidate<D> candidate = ResolutionCandidate.create(extension);
+                    candidate.setThisObject(thisObject);
+                    candidate.setReceiverArgument(receiverParameter);
+                    candidate.setExplicitReceiverKind(
+                            hasExplicitThisObject ? ExplicitReceiverKind.BOTH_RECEIVERS : ExplicitReceiverKind.THIS_OBJECT);
+                    result.add(candidate);
                 }
             }
         }
@@ -180,10 +187,12 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
         Collection<ResolutionCandidate<D>> result = Lists.newArrayList();
         for (ReceiverDescriptor receiverParameter : receiverParameters) {
             for (D descriptor : descriptors) {
-                ResolutionCandidate<D> resolvedCall = ResolutionCandidate.create(descriptor);
-                resolvedCall.setReceiverArgument(receiverParameter);
-                if (setImpliedThis(scope, resolvedCall)) {
-                    result.add(resolvedCall);
+                ResolutionCandidate<D> candidate = ResolutionCandidate.create(descriptor);
+                candidate.setReceiverArgument(receiverParameter);
+                candidate.setExplicitReceiverKind(
+                        receiverParameter.exists() ? ExplicitReceiverKind.RECEIVER_ARGUMENT : ExplicitReceiverKind.NO_EXPLICIT_RECEIVER);
+                if (setImpliedThis(scope, candidate)) {
+                    result.add(candidate);
                 }
             }
         }
@@ -195,24 +204,25 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
                     containingDeclaration = containingDeclaration.getContainingDeclaration();
                 }
                 if (containingDeclaration instanceof ClassDescriptor && ((ClassDescriptor) containingDeclaration).getKind() == ClassKind.OBJECT) {
-                    ResolutionCandidate<D> resolvedCall = ResolutionCandidate.create(descriptor);
-                    resolvedCall.setThisObject(new ClassReceiver((ClassDescriptor) containingDeclaration));
-                    result.add(resolvedCall);
+                    ResolutionCandidate<D> candidate = ResolutionCandidate.create(descriptor);
+                    candidate.setThisObject(new ClassReceiver((ClassDescriptor) containingDeclaration));
+                    candidate.setExplicitReceiverKind(ExplicitReceiverKind.NO_EXPLICIT_RECEIVER);
+                    result.add(candidate);
                 }
             }
         }
         return result;
     }
 
-    private static <D extends CallableDescriptor> boolean setImpliedThis(@NotNull JetScope scope, ResolutionCandidate<D> resolvedCall) {
-        ReceiverDescriptor expectedThisObject = resolvedCall.getDescriptor().getExpectedThisObject();
+    private static <D extends CallableDescriptor> boolean setImpliedThis(@NotNull JetScope scope, ResolutionCandidate<D> candidate) {
+        ReceiverDescriptor expectedThisObject = candidate.getDescriptor().getExpectedThisObject();
         if (!expectedThisObject.exists()) return true;
         List<ReceiverDescriptor> receivers = Lists.newArrayList();
         scope.getImplicitReceiversHierarchy(receivers);
         for (ReceiverDescriptor receiver : receivers) {
             if (JetTypeChecker.INSTANCE.isSubtypeOf(receiver.getType(), expectedThisObject.getType())) {
                 // TODO : Autocasts & nullability
-                resolvedCall.setThisObject(expectedThisObject);
+                candidate.setThisObject(expectedThisObject);
                 return true;
             }
         }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/TracingStrategy.java

@@ -72,7 +72,7 @@ import java.util.List;
         public void typeInferenceFailed(@NotNull BindingTrace trace, SolutionStatus status) {}
 
         @Override
-        public void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type) {}
+        public void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type, boolean isCallForImplicitInvoke) {}
 
         @Override
         public void unnecessarySafeCall(@NotNull BindingTrace trace, @NotNull JetType type) {}
@@ -108,7 +108,7 @@ import java.util.List;
 
     void typeInferenceFailed(@NotNull BindingTrace trace, SolutionStatus status);
 
-    void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type);
+    void unsafeCall(@NotNull BindingTrace trace, @NotNull JetType type, boolean isCallForImplicitInvoke);
 
     void unnecessarySafeCall(@NotNull BindingTrace trace, @NotNull JetType type);
 

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/VariableAsFunctionResolvedCall.java

@@ -73,6 +73,12 @@ public class VariableAsFunctionResolvedCall implements ResolvedCallWithTrace<Fun
         return variableCall.getThisObject();
     }
 
+    @NotNull
+    @Override
+    public ExplicitReceiverKind getExplicitReceiverKind() {
+        return variableCall.getExplicitReceiverKind();
+    }
+
     @NotNull
     @Override
     public Map<ValueParameterDescriptor, ResolvedValueArgument> getValueArguments() {

compiler/testData/diagnostics/tests/extensions/kt1875.jet

@@ -0,0 +1,21 @@
+//KT-1875 Safe call should be binded with receiver or this object (but not with both by default)
+
+package kt1875
+
+fun f(a : Int?, b : Int.(Int)->Int) = a?.b(1) //unnecessary safe call warning
+
+trait T {
+    val f : ((i: Int) -> Unit)?
+}
+
+fun test(t: T) {
+    t.<!UNSAFE_CALL!>f<!>(1) //unsafe call error
+    t.f?.invoke(1)
+}
+
+fun test1(t: T?) {
+    t<!UNSAFE_CALL!>.<!><!UNSAFE_CALL!>f<!>(1)
+    t?.<!UNSAFE_CALL!>f<!>(1)
+    t<!UNSAFE_CALL!>.<!>f?.invoke(1)
+    t?.f?.invoke(1)
+}

js/js.translator/src/org/jetbrains/k2js/translate/reference/CallBuilder.java

@@ -23,6 +23,7 @@ import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.descriptors.CallableDescriptor;
 import org.jetbrains.jet.lang.resolve.BindingTraceContext;
 import org.jetbrains.jet.lang.resolve.TemporaryBindingTrace;
+import org.jetbrains.jet.lang.resolve.calls.ExplicitReceiverKind;
 import org.jetbrains.jet.lang.resolve.calls.ResolutionCandidate;
 import org.jetbrains.jet.lang.resolve.calls.ResolvedCall;
 import org.jetbrains.jet.lang.resolve.calls.ResolvedCallImpl;
@@ -106,7 +107,7 @@ public final class CallBuilder {
     private CallTranslator finish() {
         if (resolvedCall == null) {
             assert descriptor != null;
-            resolvedCall = ResolvedCallImpl.create(ResolutionCandidate.create(descriptor),
+            resolvedCall = ResolvedCallImpl.create(ResolutionCandidate.create(descriptor, ExplicitReceiverKind.NO_EXPLICIT_RECEIVER),
                                                    TemporaryBindingTrace.create(new BindingTraceContext())); //todo
         }
         if (descriptor == null) {