while -> foreach: expand var when no appropriate initializer is found IDEA-193830

platform/testFramework/src/com/intellij/testFramework/PsiTestUtil.java

@@ -42,6 +42,7 @@ import com.intellij.openapi.vfs.*;
 import com.intellij.psi.PsiDocumentManager;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.impl.DebugUtil;
+import com.intellij.psi.impl.source.PsiFileImpl;
 import com.intellij.psi.stubs.StubTextInconsistencyException;
 import com.intellij.util.Function;
 import com.intellij.util.containers.ContainerUtil;
@@ -247,7 +248,11 @@ public class PsiTestUtil {
   private static PsiFile createDummyCopy(PsiFile file) {
     LightVirtualFile copy = new LightVirtualFile(file.getName(), file.getText());
     copy.setOriginalFile(file.getViewProvider().getVirtualFile());
-    return Objects.requireNonNull(file.getManager().findFile(copy));
+    PsiFile dummyCopy = Objects.requireNonNull(file.getManager().findFile(copy));
+    if (dummyCopy instanceof PsiFileImpl) {
+      ((PsiFileImpl)dummyCopy).setOriginalFile(file);
+    }
+    return dummyCopy;
   }
 
   public static void checkPsiMatchesTextIgnoringNonCode(PsiFile file) {

plugins/InspectionGadgets/src/com/siyeh/ig/migration/WhileCanBeForeachInspection.java

@@ -21,6 +21,7 @@ import com.intellij.psi.*;
 import com.intellij.psi.codeStyle.JavaCodeStyleSettings;
 import com.intellij.psi.search.searches.ReferencesSearch;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.psi.util.PsiTypesUtil;
 import com.intellij.psi.util.TypeConversionUtil;
 import com.intellij.util.Query;
 import com.siyeh.InspectionGadgetsBundle;
@@ -136,7 +137,16 @@ public class WhileCanBeForeachInspection extends WhileCanBeForeachInspectionBase
           break;
         }
         final PsiExpression expression = assignment.getRExpression();
-        initializer.delete();
+        PsiTypeElement typeElement = iterator.getTypeElement();
+        if (typeElement.isInferredType() &&
+            (expression == null || 
+             PsiType.NULL.equals(expression.getType()) || 
+             expression instanceof PsiArrayInitializerExpression || 
+             expression instanceof PsiFunctionalExpression) &&     
+            PsiTypesUtil.replaceWithExplicitType(typeElement) == null) {
+          deleteIterator = false;
+          break;
+        }
         iterator.setInitializer(expression);
         final PsiElement statement = assignment.getParent();
         final PsiElement lastChild = statement.getLastChild();

plugins/InspectionGadgets/test/com/siyeh/igfixes/migration/while_can_be_foreach/VarWithValidInitializer.after.java

@@ -0,0 +1,10 @@
+import java.util.List;
+
+class MyTest {
+    void test(List<? extends String> list) {
+        fo<caret>r (String aList: list) {
+            System.out.println(aList);
+        }
+        var it = list.iterator();
+    }
+}

plugins/InspectionGadgets/test/com/siyeh/igfixes/migration/while_can_be_foreach/VarWithValidInitializer.java

@@ -0,0 +1,11 @@
+import java.util.List;
+
+class MyTest {
+    void test(List<? extends String> list) {
+        var it = list.iterator();
+        wh<caret>ile(it.hasNext()) {
+            System.out.println(it.next());
+        }
+        it = list.iterator();
+    }
+}

plugins/InspectionGadgets/test/com/siyeh/igfixes/migration/while_can_be_foreach/VarWithoutValidInitializer.after.java

@@ -0,0 +1,11 @@
+import java.util.Iterator;
+import java.util.List;
+
+class MyTest {
+    void test(List<? extends String> list) {
+        fo<caret>r (String aList: list) {
+            System.out.println(aList);
+        }
+        Iterator<? extends String> it = null;
+    }
+}

plugins/InspectionGadgets/test/com/siyeh/igfixes/migration/while_can_be_foreach/VarWithoutValidInitializer.java

@@ -0,0 +1,11 @@
+import java.util.List;
+
+class MyTest {
+    void test(List<? extends String> list) {
+        var it = list.iterator();
+        wh<caret>ile(it.hasNext()) {
+            System.out.println(it.next());
+        }
+        it = null;
+    }
+}

plugins/InspectionGadgets/testsrc/com/siyeh/ig/fixes/migration/WhileCanBeForeachFixTest.java

@@ -15,6 +15,8 @@
  */
 package com.siyeh.ig.fixes.migration;
 
+import com.intellij.pom.java.LanguageLevel;
+import com.intellij.testFramework.builders.JavaModuleFixtureBuilder;
 import com.siyeh.InspectionGadgetsBundle;
 import com.siyeh.ig.IGQuickFixesTestCase;
 import com.siyeh.ig.migration.WhileCanBeForeachInspection;
@@ -31,6 +33,13 @@ public class WhileCanBeForeachFixTest extends IGQuickFixesTestCase {
   public void testCast() { doTest(); }
   public void testNakedNext() { doTest(); }
   public void testUnboundWildcard() { doTest(); }
+  public void testVarWithoutValidInitializer() { doTest(); }
+  public void testVarWithValidInitializer() { doTest(); }
+
+  @Override
+  protected void tuneFixture(JavaModuleFixtureBuilder builder) {
+    builder.setLanguageLevel(LanguageLevel.HIGHEST);
+  }
 
   @Override
   protected String getRelativePath() {