From ab585108daf036effd2e806680b05f8eed0bd132 Mon Sep 17 00:00:00 2001
From: gtoison <guillaume.toison@gmail.com>
Date: Tue, 11 Nov 2025 14:04:52 +0100
Subject: [PATCH] Extend SelfComparison to support time types

---
 .../bugpatterns/SelfComparison.java           |  8 +-
 .../bugpatterns/SelfComparisonTest.java       | 99 +++++++++++++++++++
 2 files changed, 106 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/SelfComparison.java b/core/src/main/java/com/google/errorprone/bugpatterns/SelfComparison.java
index 2a0102911a5..02d3c1be68b 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/SelfComparison.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/SelfComparison.java
@@ -18,6 +18,7 @@
 
 import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
 import static com.google.errorprone.matchers.Matchers.allOf;
+import static com.google.errorprone.matchers.Matchers.anyOf;
 import static com.google.errorprone.matchers.Matchers.instanceMethod;
 import static com.google.errorprone.matchers.Matchers.receiverSameAsArgument;
 
@@ -44,7 +45,12 @@ public class SelfComparison extends BugChecker implements MethodInvocationTreeMa
    */
   private static final Matcher<MethodInvocationTree> COMPARE_TO_MATCHER =
       allOf(
-          instanceMethod().onDescendantOf("java.lang.Comparable").named("compareTo"),
+          anyOf(
+              instanceMethod().onDescendantOf("java.lang.Comparable").named("compareTo"),
+              instanceMethod().onDescendantOf("java.util.Date").namedAnyOf("after", "before"),
+              instanceMethod().onDescendantOf("java.time.Instant").namedAnyOf("isAfter", "isBefore"),
+              instanceMethod().onDescendantOf("java.time.chrono.ChronoLocalDate").namedAnyOf("isAfter", "isBefore"),
+              instanceMethod().onDescendantOf("java.time.chrono.ChronoLocalDateTime").namedAnyOf("isAfter", "isBefore")),
           receiverSameAsArgument(0));
 
   @Override
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/SelfComparisonTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/SelfComparisonTest.java
index 5cff2449df4..e77f0c804fd 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/SelfComparisonTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/SelfComparisonTest.java
@@ -167,4 +167,103 @@ public int compareTo(CopmarisonTest obj) {
             """)
         .doTest();
   }
+
+  @Test
+  public void localDatePositiveCase() {
+    compilationHelper
+        .addSourceLines(
+            "LocalDateSelfComparisonPositiveCase.java",
+            """
+            package com.google.errorprone.bugpatterns.testdata;
+            
+            import java.time.LocalDate;
+
+            public class LocalDateSelfComparisonPositiveCase {
+
+              public boolean test1() {
+                LocalDate date = LocalDate.of(2025, 11, 10);
+                // BUG: Diagnostic contains: An object is compared to itself
+                return date.isAfter(date);
+              }
+
+              private LocalDate date = LocalDate.of(2025, 11, 10);
+
+              public boolean test2() {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return date.isAfter(this.date);
+              }
+
+              public boolean test3() {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return this.date.isBefore(date);
+              }
+
+              public boolean test4() {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return this.date.isBefore(this.date);
+              }
+            }\
+            """)
+        .doTest();
+  }
+
+  @Test
+  public void timeTypesPositiveCase() {
+    compilationHelper
+        .addSourceLines(
+            "TimeTypesSelfComparisonPositiveCase.java",
+            """
+            package com.google.errorprone.bugpatterns.testdata;
+            
+            import java.time.Instant;
+            import java.time.LocalDate;
+            import java.time.LocalDateTime;
+            import java.time.LocalDate;
+            import java.util.Date;
+
+            public class TimeTypesSelfComparisonPositiveCase {
+
+              public boolean testInstantAfter(Instant x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isAfter(x);
+              }
+
+              public boolean testInstantBefore(Instant x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isBefore(x);
+              }
+
+              public boolean testLocalDateAfter(LocalDate x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isAfter(x);
+              }
+
+              public boolean testLocalDateBefore(LocalDate x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isBefore(x);
+              }
+
+              public boolean testLocalDateTimeAfter(LocalDateTime x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isAfter(x);
+              }
+
+              public boolean testLocalDateTimeBefore(LocalDateTime x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.isBefore(x);
+              }
+
+              public boolean testDateAfter(Date x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.after(x);
+              }
+
+              public boolean testDateBefore(Date x) {
+                // BUG: Diagnostic contains: An object is compared to itself
+                return x.before(x);
+              }
+            }\
+            """)
+        .doTest();
+  }
 }