KT-3174 Call resolver doesn't understand type is not-nullable after ?. safe call

#KT-3174 fixed

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

@@ -276,8 +276,11 @@ public class CandidateResolver {
         ReceiverValue receiverArgument = candidateCall.getReceiverArgument();
         ReceiverParameterDescriptor receiverParameter = candidateWithFreshVariables.getReceiverParameter();
         if (receiverArgument.exists() && receiverParameter != null) {
-            constraintsSystem.addSubtypeConstraint(receiverParameter.getType(), receiverArgument.getType(),
-                                                   ConstraintPosition.RECEIVER_POSITION);
+            JetType receiverType =
+                    context.candidateCall.isSafeCall()
+                    ? TypeUtils.makeNotNullable(receiverArgument.getType())
+                    : receiverArgument.getType();
+            constraintsSystem.addSubtypeConstraint(receiverParameter.getType(), receiverType, ConstraintPosition.RECEIVER_POSITION);
         }
 
         ConstraintSystem

compiler/testData/diagnostics/tests/inference/regressions/kt3174.kt

@@ -0,0 +1,12 @@
+//KT-3174 Call resolver doesn't understand type is not-nullable after ?. safe call
+package a
+
+fun <T: Any> T.test(): T = this
+fun foo(a: Any?) = a?.test() // Error
+
+fun <T> T.fff(l: MutableList<T>) = l.add(this)
+
+fun test(s: String?, l: MutableList<String>) {
+    s?.fff(l)
+
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -2247,6 +2247,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                     doTest("compiler/testData/diagnostics/tests/inference/regressions/kt3150.kt");
                 }
                 
+                @TestMetadata("kt3174.kt")
+                public void testKt3174() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/inference/regressions/kt3174.kt");
+                }
+                
                 @TestMetadata("kt702.kt")
                 public void testKt702() throws Exception {
                     doTest("compiler/testData/diagnostics/tests/inference/regressions/kt702.kt");