Smart completion after ?: works incorrectly

#KT-4926 Fixed

idea/src/org/jetbrains/jet/plugin/completion/ExpectedInfos.kt

@@ -50,7 +50,6 @@ import org.jetbrains.jet.lang.resolve.calls.util.DelegatingCall
 import org.jetbrains.jet.lang.resolve.calls.util.noErrorsInValueArguments
 import org.jetbrains.jet.lang.resolve.calls.util.hasUnmappedParameters
 import org.jetbrains.jet.lang.descriptors.Visibilities
-import org.jetbrains.jet.lang.descriptors.DeclarationDescriptorWithVisibility
 
 enum class Tail {
     COMMA
@@ -66,6 +65,7 @@ class ExpectedInfos(val bindingContext: BindingContext, val moduleDescriptor: Mo
             ?: calculateForFunctionLiteralArgument(expressionWithType)
             ?: calculateForEq(expressionWithType)
             ?: calculateForIf(expressionWithType)
+            ?: calculateForElvis(expressionWithType)
             ?: getFromBindingContext(expressionWithType)
     }
 
@@ -186,6 +186,28 @@ class ExpectedInfos(val bindingContext: BindingContext, val moduleDescriptor: Mo
         }
     }
 
+    private fun calculateForElvis(expressionWithType: JetExpression): Collection<ExpectedInfo>? {
+        val binaryExpression = expressionWithType.getParent() as? JetBinaryExpression
+        if (binaryExpression != null) {
+            val operationToken = binaryExpression.getOperationToken()
+            if (operationToken == JetTokens.ELVIS && expressionWithType == binaryExpression.getRight()) {
+                val otherOperand = binaryExpression.getLeft() ?: return null
+                val otherOperandType = bindingContext[BindingContext.EXPRESSION_TYPE, otherOperand]
+                val expectedInfos = calculate(binaryExpression)
+                if (expectedInfos != null) {
+                    return if (otherOperandType != null)
+                        expectedInfos.filter { it.`type`.isSubtypeOf(otherOperandType) }
+                    else
+                        expectedInfos
+                }
+                else if (otherOperandType != null) {
+                    return listOf(ExpectedInfo(TypeUtils.makeNotNullable(otherOperandType), null))
+                }
+            }
+        }
+        return null
+    }
+
     private fun getFromBindingContext(expressionWithType: JetExpression): Collection<ExpectedInfo>? {
         val expectedType = bindingContext[BindingContext.EXPECTED_EXPRESSION_TYPE, expressionWithType] ?: return null
         return listOf(ExpectedInfo(expectedType, null))

idea/testData/completion/handlers/smart/InElvisOperator.kt

@@ -0,0 +1,7 @@
+fun foo(s: String, c: Char){}
+
+fun bar(p1: String?, p2: String) {
+    foo(p1 ?: <caret>
+}
+
+// ELEMENT: p2

idea/testData/completion/handlers/smart/InElvisOperator.kt.after

@@ -0,0 +1,7 @@
+fun foo(s: String, c: Char){}
+
+fun bar(p1: String?, p2: String) {
+    foo(p1 ?: p2, <caret>
+}
+
+// ELEMENT: p2

idea/testData/completion/smart/InElvisOperator1.kt

@@ -0,0 +1,9 @@
+fun foo(p: String?){}
+fun foo(p: Char){}
+
+fun bar(p1: String?, p2: String?, p3: Char) {
+    foo(p1 ?: <caret>
+}
+
+// EXIST: { itemText:"p2" }
+// ABSENT: p3

idea/testData/completion/smart/InElvisOperator2.kt

@@ -0,0 +1,12 @@
+fun foo1(): String? = null
+fun foo2(): String? = null
+fun foo3(): String = ""
+
+fun bar() {
+    foo1() ?: <caret>
+}
+
+// EXIST: { itemText:"foo3()" }
+// ABSENT: { itemText:"foo2()" }
+// EXIST: { itemText:"!! foo2()" }
+// EXIST: { itemText:"?: foo2()" }

idea/tests/org/jetbrains/jet/completion/JvmSmartCompletionTestGenerated.java

@@ -216,6 +216,16 @@ public class JvmSmartCompletionTestGenerated extends AbstractJvmSmartCompletionT
         doTest("idea/testData/completion/smart/IfValue3.kt");
     }
     
+    @TestMetadata("InElvisOperator1.kt")
+    public void testInElvisOperator1() throws Exception {
+        doTest("idea/testData/completion/smart/InElvisOperator1.kt");
+    }
+    
+    @TestMetadata("InElvisOperator2.kt")
+    public void testInElvisOperator2() throws Exception {
+        doTest("idea/testData/completion/smart/InElvisOperator2.kt");
+    }
+    
     @TestMetadata("InaccessibleConstructor.kt")
     public void testInaccessibleConstructor() throws Exception {
         doTest("idea/testData/completion/smart/InaccessibleConstructor.kt");

idea/tests/org/jetbrains/jet/completion/handlers/SmartCompletionHandlerTestGenerated.java

@@ -226,6 +226,11 @@ public class SmartCompletionHandlerTestGenerated extends AbstractSmartCompletion
         doTest("idea/testData/completion/handlers/smart/IfValue3.kt");
     }
     
+    @TestMetadata("InElvisOperator.kt")
+    public void testInElvisOperator() throws Exception {
+        doTest("idea/testData/completion/handlers/smart/InElvisOperator.kt");
+    }
+    
     @TestMetadata("JavaEnumMemberInsertsImport.kt")
     public void testJavaEnumMemberInsertsImport() throws Exception {
         doTest("idea/testData/completion/handlers/smart/JavaEnumMemberInsertsImport.kt");