Java: Highlight unreachable assignment of array element (IDEA-199556)

java/java-psi-impl/src/com/intellij/psi/controlFlow/ControlFlowAnalyzer.java

@@ -1324,6 +1324,7 @@ class ControlFlowAnalyzer extends JavaElementVisitor {
     myStartStatementStack.pushStatement(rExpr == null ? expression : rExpr, false);
     myEndStatementStack.pushStatement(rExpr == null ? expression : rExpr, false);
 
+    boolean generatedWriteInstruction = false;
     PsiExpression lExpr = PsiUtil.skipParenthesizedExprDown(expression.getLExpression());
     if (lExpr instanceof PsiReferenceExpression) {
       PsiVariable variable = getUsedVariable((PsiReferenceExpression)lExpr);
@@ -1344,6 +1345,7 @@ class ControlFlowAnalyzer extends JavaElementVisitor {
           rExpr.accept(this);
         }
         generateWriteInstruction(variable);
+        generatedWriteInstruction = true;
 
         if (myAssignmentTargetsAreElements) finishElement(lExpr);
       }
@@ -1376,6 +1378,8 @@ class ControlFlowAnalyzer extends JavaElementVisitor {
         rExpr.accept(this);
       }
     }
+    //each statement should contain at least one instruction in order to getElement(offset) work
+    if (!generatedWriteInstruction) emitEmptyInstruction();
 
     myStartStatementStack.popStatement();
     myEndStatementStack.popStatement();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting/UnreachableArrayElementAssignment.java

@@ -0,0 +1,7 @@
+class C {
+  void foo(String arg) throws Exception {
+    Object[] objects;
+    throw new Exception("");
+    <error descr="Unreachable statement">objects[0] = arg;</error>
+  }
+}

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

@@ -418,6 +418,8 @@ public class LightAdvHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest(false);
   }
 
+  public void testUnreachableArrayElementAssignment() { doTest(false); }
+
   public void testInsane() {
     configureFromFileText("x.java", "class X { \nx_x_x_x\n }");
     List<HighlightInfo> infos = highlightErrors();