Add type aliases into UnusedSymbolInspection / safe delete

So #KT-16046 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedSymbolInspection.kt

@@ -145,6 +145,7 @@ class UnusedSymbolInspection : AbstractKotlinInspection() {
                     is KtSecondaryConstructor -> "Constructor is never used"
                     is KtProperty, is KtParameter -> "Property ''$name'' is never used"
                     is KtTypeParameter -> "Type parameter ''$name'' is never used"
+                    is KtTypeAlias -> "Type alias ''$name'' is never used"
                     else -> return
                 }
 

idea/src/org/jetbrains/kotlin/idea/refactoring/safeDelete/utils.kt

@@ -49,6 +49,7 @@ fun PsiElement.canDeleteElement(): Boolean {
         || this is PsiClass
         || this is KtProperty
         || this is KtTypeParameter
+        || this is KtTypeAlias
 }
 
 fun PsiElement.removeOverrideModifier() {

idea/testData/inspections/unusedSymbol/typeAlias/inspectionData/expected.xml

@@ -0,0 +1,18 @@
+<problems>
+    <problem>
+        <file>test.kt</file>
+        <line>4</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
+        <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused symbol</problem_class>
+        <description>Type alias ''YourString'' is never used</description>
+    </problem>
+    <problem>
+        <file>test.kt</file>
+        <line>6</line>
+        <module>light_idea_test_case</module>
+        <entry_point TYPE="file" FQNAME="temp:///src/test.kt" />
+        <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused symbol</problem_class>
+        <description>Property ''ms'' is never used</description>
+    </problem>
+</problems>

idea/testData/inspections/unusedSymbol/typeAlias/inspectionData/inspections.test

@@ -0,0 +1 @@
+// INSPECTION_CLASS: org.jetbrains.kotlin.idea.inspections.UnusedSymbolInspection

idea/testData/inspections/unusedSymbol/typeAlias/test.kt

@@ -0,0 +1,6 @@
+typealias MyString = String
+
+// unused
+typealias YourString = String
+
+val ms: MyString = ""

idea/tests/org/jetbrains/kotlin/idea/codeInsight/InspectionTestGenerated.java

@@ -413,6 +413,12 @@ public class InspectionTestGenerated extends AbstractInspectionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("unusedSymbol/typeAlias/inspectionData/inspections.test")
+        public void testUnusedSymbol_typeAlias_inspectionData_Inspections_test() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspections/unusedSymbol/typeAlias/inspectionData/inspections.test");
+            doTest(fileName);
+        }
+
         @TestMetadata("unusedSymbol/typeParameter/inspectionData/inspections.test")
         public void testUnusedSymbol_typeParameter_inspectionData_Inspections_test() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspections/unusedSymbol/typeParameter/inspectionData/inspections.test");