From b0632d031590e93a7f149b4ff2af26d3413e54c6 Mon Sep 17 00:00:00 2001
From: Stephan Schroevers <stephan.schroevers@teampicnic.com>
Date: Mon, 2 Jan 2023 21:53:53 +0100
Subject: [PATCH] StatementSwitchToExpressionSwitch: skip rule cases

The cases in a switch statement must all be of kind `STATEMENT` or
`RULE`. In the latter case `StatementSwitchToExpressionSwitch` does not
apply.
---
 .../StatementSwitchToExpressionSwitch.java    | 16 ++++++++++++--
 ...StatementSwitchToExpressionSwitchTest.java | 21 ++++++++++++++++++-
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java b/core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java
index b9181a5091f..cca422b8247 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java
@@ -86,7 +86,7 @@ public StatementSwitchToExpressionSwitch(ErrorProneFlags flags) {
 
   @Override
   public Description matchSwitch(SwitchTree switchTree, VisitorState state) {
-    if (!SourceVersion.supportsSwitchExpressions(state.context)) {
+    if (!SourceVersion.supportsSwitchExpressions(state.context) || isRuleSwitch(switchTree)) {
       return NO_MATCH;
     }
 
@@ -99,6 +99,18 @@ public Description matchSwitch(SwitchTree switchTree, VisitorState state) {
     return NO_MATCH;
   }
 
+  private static boolean isRuleSwitch(SwitchTree switchTree) {
+    return switchTree.getCases().stream().anyMatch(StatementSwitchToExpressionSwitch::isRuleCase);
+  }
+
+  private static boolean isRuleCase(CaseTree caseTree) {
+    try {
+      return "RULE".equals(CaseTree.class.getMethod("getCaseKind").invoke(caseTree).toString());
+    } catch (ReflectiveOperationException e) {
+      throw new LinkageError(e.getMessage(), e);
+    }
+  }
+
   /**
    * Analyzes a {@code SwitchTree}, and determines any possible findings and suggested fixes related
    * to expression switches that can be made. Does not report any findings or suggested fixes up to
@@ -122,7 +134,7 @@ private static AnalysisResult analyzeSwitchTree(SwitchTree switchTree) {
 
       List<? extends StatementTree> statements = caseTree.getStatements();
       CaseFallThru caseFallThru = CaseFallThru.MAYBE_FALLS_THRU;
-      if (statements == null || statements.isEmpty()) {
+      if (statements.isEmpty()) {
         // If the code for this case is just an empty block, then it must fall thru
         caseFallThru = CaseFallThru.DEFINITELY_DOES_FALL_THRU;
         // Can group with the next case (unless this is the last case)
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitchTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitchTest.java
index 623ee82f4b7..d7e15766beb 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitchTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitchTest.java
@@ -1017,7 +1017,7 @@ public void singleCaseConvertible_error() {
   }
 
   @Test
-  public void emptySwitchCases_noMatch() {
+  public void emptyRuleSwitchCases_noMatch() {
     assumeTrue(RuntimeVersion.isAtLeast14());
     helper
         .addSourceLines(
@@ -1030,6 +1030,25 @@ public void emptySwitchCases_noMatch() {
             "    }",
             "  }",
             "}")
+        .setArgs("-XepOpt:StatementSwitchToExpressionSwitch:EnableDirectConversion")
+        .doTest();
+  }
+
+  @Test
+  public void voidRuleSwitchCases_noMatch() {
+    assumeTrue(RuntimeVersion.isAtLeast14());
+    helper
+        .addSourceLines(
+            "Test.java",
+            "class Test {",
+            "  void foo(int value) { ",
+            "    switch (value) {",
+            "      case 0 -> { System.out.println(\"zero\");  }",
+            "      case 1 -> { System.out.println(\"one\"); }",
+            "    }",
+            "  }",
+            "}")
+        .setArgs("-XepOpt:StatementSwitchToExpressionSwitch:EnableDirectConversion")
         .doTest();
   }