[java-intentions] Add fix to replace an unresolved type with initializer type

Fixes IDEA-225526 Replace var with inferred type in Java 9 or below

GitOrigin-RevId: 465b0163a2a8b3e8f0346b350a5e373d9b958817

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

@@ -656,6 +656,7 @@ public final class DefaultJavaErrorFixProvider extends AbstractJavaErrorFixProvi
     fixes(EXPRESSION_SUPER_UNQUALIFIED_DEFAULT_METHOD, (error, sink) ->
       QualifySuperArgumentFix.registerQuickFixAction(error.context(), sink));
     fix(REFERENCE_UNRESOLVED, error -> HighlightFixUtil.createUnresolvedReferenceFix(error.psi()));
+    fix(REFERENCE_UNRESOLVED, error -> HighlightFixUtil.createVariableTypeFix(error.psi()));
     fix(REFERENCE_QUALIFIER_PRIMITIVE,
         error -> error.psi() instanceof PsiReferenceExpression ref ? myFactory.createRenameWrongRefFix(ref) : null);
     fix(CAST_INTERSECTION_NOT_INTERFACE, error -> {

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

@@ -25,6 +25,7 @@ import com.intellij.pom.java.JavaFeature;
 import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.*;
 import com.intellij.psi.controlFlow.*;
+import com.intellij.psi.impl.IncompleteModelUtil;
 import com.intellij.psi.infos.CandidateInfo;
 import com.intellij.psi.infos.MethodCandidateInfo;
 import com.intellij.psi.search.GlobalSearchScope;
@@ -1116,6 +1117,19 @@ public final class HighlightFixUtil {
       .toList();
   }
 
+  static @Nullable CommonIntentionAction createVariableTypeFix(PsiJavaCodeReferenceElement ref) {
+    if (!(ref.getParent() instanceof PsiTypeElement typeElement)) return null;
+    if (!(typeElement.getParent() instanceof PsiLocalVariable localVariable)) return null;
+    PsiExpression initializer = localVariable.getInitializer();
+    if (initializer == null) return null;
+    PsiType type = initializer.getType();
+    if (type == null || !PsiTypesUtil.isDenotableType(type, localVariable)) return null;
+    if (PsiTypes.voidType().equals(type) || PsiTypes.nullType().equals(type)) return null;
+    if (IncompleteModelUtil.hasUnresolvedComponent(type)) return null;
+    return PriorityIntentionActionWrapper.highPriority(
+      QuickFixFactory.getInstance().createSetVariableTypeFix(localVariable, type));
+  }
+
   private static final class ReturnModel {
     final PsiReturnStatement myStatement;
     final PsiType myType;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/setVariableType/afterUnresolvedType.java

@@ -0,0 +1,6 @@
+// "Set variable type to 'int'" "true-preview"
+public class Demo {
+  void test() {
+    int s = 123;
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/setVariableType/beforeUnresolvedType.java

@@ -0,0 +1,6 @@
+// "Set variable type to 'int'" "true-preview"
+public class Demo {
+  void test() {
+    in<caret>tt s = 123;
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/setVariableType/beforeUnresolvedTypeBothSide.java

@@ -0,0 +1,6 @@
+// "Set variable type to 'intt'" "false"
+public class Demo {
+  void test(intt s1) {
+    in<caret>tt s = s1;
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/setVariableType/beforeUnresolvedTypeNoInitializer.java

@@ -0,0 +1,7 @@
+// "Set variable type to 'int'" "false"
+public class Demo {
+  void test() {
+    in<caret>tt s;
+    s = 123;
+  }
+}