[java-inspections] Do not treat import as unused if it's a potentinally class-import

Fixes IDEA-372121 Optimize imports does nothing on unresolved reference

GitOrigin-RevId: e70ceab4f23092e2b7f7a84edbc0c4159c504084

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/LocalRefUseInfo.java

@@ -388,6 +388,12 @@ public final class LocalRefUseInfo {
           }
         }
       }
+      else if (ref instanceof PsiJavaCodeReferenceElement javaRef && refElement instanceof PsiVariable &&
+               IncompleteModelUtil.canBeClassReference(javaRef)) {
+        for (PsiImportStatementBase potentialImport : IncompleteModelUtil.getPotentialImports(javaRef)) {
+          registerImportStatement(potentialImport);
+        }
+      }
     }
 
     @Override

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/unusedImports/UnresolvedReferenceAsVariableAndClass.java

@@ -0,0 +1,10 @@
+import com.<error descr="Cannot resolve symbol 'intellij'">intellij</error>.lang.javascript.JavaScriptFileType;
+import com.<error descr="Cannot resolve symbol 'intellij'">intellij</error>.template.lang.core.templateLanguages.TemplatesService;
+
+public class UnresolvedReferenceAsVariableAndClass {
+  public void setUp() {
+    Object <warning descr="Variable 'TemplatesService' is never assigned">TemplatesService</warning>;
+    final <error descr="Unknown class: 'TemplatesService'">TemplatesService</error> <warning descr="Variable 'service' is never used">service</warning> = <error descr="Variable 'TemplatesService' might not have been initialized">TemplatesService</error>.getInstance();
+    System.out.println(<error descr="Cannot resolve symbol 'JavaScriptFileType'">JavaScriptFileType</error>.INSTANCE);
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/daemon/UnusedImportsTest.java

@@ -92,6 +92,10 @@ public class UnusedImportsTest extends LightJavaCodeInsightFixtureTestCase {
     doTest();
   }
 
+  public void testUnresolvedReferenceAsVariableAndClass() {
+    doTest();
+  }
+
   public void testImportsForUsesAndProvidesInModuleInfo() {
     myFixture.addClass("""
                          package pkg.main.api;