From bbcc8ca24d02012d137207ab5bf1eafd20ca2ba8 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Mon, 1 Oct 2018 16:06:01 +0700
Subject: [PATCH] IDEA-199693 Unreachable switch statements are not highlighted
 after always reachable branch

---
 .../dataFlow/DataFlowInspectionBase.java      | 13 +++++-
 .../fixture/AlwaysTrueSwitchLabel.java        | 43 +++++++++++++++++++
 .../DataFlowInspectionTest.java               |  1 +
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 java/java-tests/testData/inspection/dataFlow/fixture/AlwaysTrueSwitchLabel.java

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DataFlowInspectionBase.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DataFlowInspectionBase.java
index 54421e1bbd31..9d988642ec6b 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DataFlowInspectionBase.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/DataFlowInspectionBase.java
@@ -43,7 +43,6 @@ import java.util.*;
 
 import static com.intellij.util.ObjectUtils.tryCast;
 
-@SuppressWarnings("ConditionalExpressionWithIdenticalBranches")
 public class DataFlowInspectionBase extends AbstractBaseJavaLocalInspectionTool {
   static final Logger LOG = Logger.getInstance("#com.intellij.codeInspection.dataFlow.DataFlowInspection");
   @NonNls private static final String SHORT_NAME = "ConstantConditions";
@@ -692,6 +691,18 @@ public class DataFlowInspectionBase extends AbstractBaseJavaLocalInspectionTool
         holder.registerProblem(psiAnchor,
                                InspectionsBundle.message("dataflow.message.unreachable.switch.label"),
                                new DeleteSwitchLabelFix((PsiSwitchLabelStatement)psiAnchor));
+      } else if (trueSet.contains(instruction)) {
+        // If switch branch is always reachable, then all the subsequent branches are unreachable (thus weren't analyzed)
+        PsiSwitchLabelStatement current = (PsiSwitchLabelStatement)psiAnchor;
+        while(true) {
+          current = PsiTreeUtil.getNextSiblingOfType(current, PsiSwitchLabelStatement.class);
+          if (current == null) break;
+          if (!current.isDefaultCase()) {
+            holder.registerProblem(current,
+                                   InspectionsBundle.message("dataflow.message.unreachable.switch.label"),
+                                   new DeleteSwitchLabelFix((PsiSwitchLabelStatement)psiAnchor));
+          }
+        }
       }
     }
     else if (psiAnchor != null && !isFlagCheck(psiAnchor)) {
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/AlwaysTrueSwitchLabel.java b/java/java-tests/testData/inspection/dataFlow/fixture/AlwaysTrueSwitchLabel.java
new file mode 100644
index 000000000000..3f69d76d5e53
--- /dev/null
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/AlwaysTrueSwitchLabel.java
@@ -0,0 +1,43 @@
+class Scratch {
+  public static void main(String[] args) {
+    switch("ping") {
+      case "ping":
+        System.out.println("ping");
+        break;
+      <warning descr="Switch label 'case \"pong\":' is unreachable">case "pong":</warning>
+        System.out.println("pong");
+        break;
+      <warning descr="Switch label 'case \"simple\":' is unreachable">case "simple":</warning>
+        System.out.println("simple");
+        break;
+      default:
+        break;
+    }
+    switch("ping") {
+      <warning descr="Switch label 'case \"pong\":' is unreachable">case "pong":</warning>
+        System.out.println("pong");
+        break;
+      case "ping":
+        System.out.println("ping");
+        break;
+      <warning descr="Switch label 'case \"simple\":' is unreachable">case "simple":</warning>
+        System.out.println("simple");
+        break;
+      default:
+        break;
+    }
+    switch("ping") {
+      <warning descr="Switch label 'case \"pong\":' is unreachable">case "pong":</warning>
+        System.out.println("pong");
+        break;
+      <warning descr="Switch label 'case \"simple\":' is unreachable">case "simple":</warning>
+        System.out.println("simple");
+        break;
+      case "ping":
+        System.out.println("ping");
+        break;
+      default:
+        break;
+    }
+  }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspectionTest.java b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspectionTest.java
index 2751d3bc1424..8326120979a1 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspectionTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInspection/DataFlowInspectionTest.java
@@ -657,4 +657,5 @@ public class DataFlowInspectionTest extends DataFlowInspectionTestCase {
     assertEquals(1, intentions.stream().filter(i -> i.getText().equals("Remove 'if' statement")).count());
     assertEquals(0, intentions.stream().filter(i -> i.getText().equals("Simplify 'expirationDay != other.expirationDay' to false")).count());
   }
+  public void testAlwaysTrueSwitchLabel() { doTest(); }
 }