Fixed KT-5158 Smart completion for when selector: do not include subject variable

#KT-5158 Fixed

idea/src/org/jetbrains/jet/plugin/completion/smart/SmartCompletion.kt

@@ -151,10 +151,19 @@ class SmartCompletion(val expression: JetSimpleNameExpression,
                 val entry = parent.getParent() as JetWhenEntry
                 val whenExpression = entry.getParent() as JetWhenExpression
                 val subject = whenExpression.getSubjectExpression() ?: return setOf()
+
+                val itemsToSkip = HashSet<DeclarationDescriptor>()
+
+                if (subject is JetSimpleNameExpression) {
+                    val variable = bindingContext[BindingContext.REFERENCE_TARGET, subject] as? VariableDescriptor
+                    if (variable != null) {
+                        itemsToSkip.add(variable)
+                    }
+                }
+
                 val subjectType = bindingContext[BindingContext.EXPRESSION_TYPE, subject] ?: return setOf()
                 val classDescriptor = TypeUtils.getClassDescriptor(subjectType)
                 if (classDescriptor != null && DescriptorUtils.isEnumClass(classDescriptor)) {
-                    val usedEnumEntries = HashSet<ClassDescriptor>()
                     val conditions = whenExpression.getEntries()
                             .flatMap { it.getConditions().toList() }
                             .filterIsInstance(javaClass<JetWhenConditionWithExpression>())
@@ -163,11 +172,12 @@ class SmartCompletion(val expression: JetSimpleNameExpression,
                                 ?.getSelectorExpression() as? JetReferenceExpression ?: continue
                         val target = bindingContext[BindingContext.REFERENCE_TARGET, selectorExpr] as? ClassDescriptor ?: continue
                         if (DescriptorUtils.isEnumEntry(target)) {
-                            usedEnumEntries.add(target)
+                            itemsToSkip.add(target)
                         }
                     }
-                    return usedEnumEntries
                 }
+
+                return itemsToSkip
             }
         }
         return setOf()

idea/testData/completion/smart/WhenEntryValue8.kt

@@ -9,3 +9,4 @@ fun foo(e: ElementType) {
 
 // ABSENT: ElementType.FIELD
 // EXIST: ElementType.TYPE
+// ABSENT: e

idea/testData/completion/smart/WhenEntryValue9.kt

@@ -0,0 +1,8 @@
+fun foo(p1: String, p2: String) {
+    when (p1) {
+        <caret>
+    }
+}
+
+// ABSENT: p1
+// EXIST: p2

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

@@ -516,6 +516,11 @@ public class JvmSmartCompletionTestGenerated extends AbstractJvmSmartCompletionT
         doTest("idea/testData/completion/smart/WhenEntryValue8.kt");
     }
     
+    @TestMetadata("WhenEntryValue9.kt")
+    public void testWhenEntryValue9() throws Exception {
+        doTest("idea/testData/completion/smart/WhenEntryValue9.kt");
+    }
+    
     @TestMetadata("WhenWithNoSubjectEntryValue1.kt")
     public void testWhenWithNoSubjectEntryValue1() throws Exception {
         doTest("idea/testData/completion/smart/WhenWithNoSubjectEntryValue1.kt");