[java-injection] Allow reassigning STR to language-specific constant (IDEA-333006)

GitOrigin-RevId: 29656ea1e3c85f350fe969c1b7025c1d18f0a2b9

plugins/IntelliLang/IntelliLang-tests/test/org/intellij/plugins/intelliLang/inject/java/validation/LanguageMismatchTest.java

@@ -16,7 +16,9 @@
 package org.intellij.plugins.intelliLang.inject.java.validation;
 
 import com.intellij.codeInsight.intention.IntentionAction;
+import com.intellij.testFramework.LightProjectDescriptor;
 import com.intellij.testFramework.fixtures.LightJavaCodeInsightFixtureTestCase;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author Bas Leijdekkers
@@ -30,6 +32,11 @@ public class LanguageMismatchTest extends LightJavaCodeInsightFixtureTestCase {
     myFixture.enableInspections(inspection);
   }
 
+  @Override
+  protected @NotNull LightProjectDescriptor getProjectDescriptor() {
+    return JAVA_21_ANNOTATED;
+  }
+
   public void testParenthesesHighlighting() {
     highlightTest("""
       import org.intellij.lang.annotations.Language;
@@ -66,6 +73,16 @@ public class LanguageMismatchTest extends LightJavaCodeInsightFixtureTestCase {
     }
     """, "Annotate field 'JS_CODE' as '@Language'");
   }
+  
+  public void testProcessorReassigned() {
+    highlightTest("""
+                      import org.intellij.lang.annotations.Language;
+                      
+                      class Hello {
+                          @Language("JAVA")
+                          public static final StringTemplate.Processor<String, RuntimeException> JAVA = STR;
+                      }""");
+  }
 
   public void testEmptyArrayConstant() {
     highlightTest("""

plugins/IntelliLang/java-support/org/intellij/plugins/intelliLang/inject/java/validation/LanguageMismatch.java

@@ -24,7 +24,9 @@ import com.intellij.codeInspection.options.OptPane;
 import com.intellij.openapi.util.Pair;
 import com.intellij.openapi.util.text.HtmlChunk;
 import com.intellij.psi.*;
+import com.intellij.psi.util.JavaPsiStringTemplateUtil;
 import com.intellij.psi.util.PsiTreeUtil;
+import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.ArrayUtil;
 import com.intellij.util.SmartList;
 import com.siyeh.ig.psiutils.CollectionUtils;
@@ -99,20 +101,24 @@ public class LanguageMismatch extends LocalInspectionTool {
               }
             }
             else if (CHECK_NON_ANNOTATED_REFERENCES) {
-              final PsiElement var =
+              final PsiElement decl =
                   PsiTreeUtil.getParentOfType(expression, PsiVariable.class, PsiExpressionList.class, PsiAssignmentExpression.class);
               // only nag about direct assignment or passing the reference as parameter
-              if (var instanceof PsiVariable) {
-                if (((PsiVariable)var).getInitializer() != expression) {
+              if (decl instanceof PsiVariable variable) {
+                if (variable.getInitializer() != expression) {
+                  return;
+                }
+                if (JavaPsiStringTemplateUtil.isStrTemplate(expression)) {
+                  // Allow reassigning STR processor to apply language for standard concatenation
                   return;
                 }
               }
-              else if (var instanceof PsiExpressionList list) {
+              else if (decl instanceof PsiExpressionList list) {
                 if (!ArrayUtil.contains(expression, list.getExpressions())) {
                   return;
                 }
               }
-              else if (var instanceof PsiAssignmentExpression a) {
+              else if (decl instanceof PsiAssignmentExpression a) {
                 if (a.getRExpression() != expression) {
                   return;
                 }