From 5a7b8d9b41a19aaf6cc917bc295ab5201cc2f328 Mon Sep 17 00:00:00 2001
From: ghm <ghm@google.com>
Date: Mon, 15 Apr 2024 05:11:01 -0700
Subject: [PATCH] NearbyCallers: scan the body of expression lambdas.

PiperOrigin-RevId: 624922054
---
 .../bugpatterns/time/NearbyCallers.java        |  5 ++---
 .../JavaDurationGetSecondsGetNanoTest.java     | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/time/NearbyCallers.java b/core/src/main/java/com/google/errorprone/bugpatterns/time/NearbyCallers.java
index 4f485341543..98a3646f9d9 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/time/NearbyCallers.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/time/NearbyCallers.java
@@ -167,8 +167,7 @@ private static ImmutableList<Tree> getNearbyTreesToScan(VisitorState state) {
           return ImmutableList.of(parent);
 
         case LAMBDA_EXPRESSION:
-          // if we reach a lambda tree, then don't scan anything since we don't know where/when that
-          // lambda will actually be executed.
+          // if we reach a lambda tree, just scan the lambda body itself
           // TODO(glorioso): for simple expression lambdas, consider looking for use sites and scan
           // *those* sites, but binding the lambda variable to its use site might be rough :(
 
@@ -179,7 +178,7 @@ private static ImmutableList<Tree> getNearbyTreesToScan(VisitorState state) {
           //   long nanos = NANOS.apply(myDuration) + SECONDS.apply(myDuration) * 1_000_000L;
           //
           // how do we track myDuration through both layers?
-          return ImmutableList.of();
+          return ImmutableList.of(((LambdaExpressionTree) parent).getBody());
 
         case CLASS:
           // if we get all the way up to the class tree, then _only_ scan the other class-level
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/time/JavaDurationGetSecondsGetNanoTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/time/JavaDurationGetSecondsGetNanoTest.java
index e8d2bf2ca10..a84f9034b65 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/time/JavaDurationGetSecondsGetNanoTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/time/JavaDurationGetSecondsGetNanoTest.java
@@ -324,4 +324,22 @@ public void getNanoInLambda() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void bothUsedWithinALambda() {
+    compilationHelper
+        .addSourceLines(
+            "test/TestCase.java",
+            "package test;",
+            "import com.google.common.collect.ImmutableMap;",
+            "import java.time.Duration;",
+            "import java.util.function.Supplier;",
+            "public class TestCase {",
+            "  public static Supplier<ImmutableMap<String, Object>> foo(Duration duration) {",
+            "    return () -> ImmutableMap.of(",
+            "        \"seconds\", duration.getSeconds(), \"nanos\", duration.getNano());",
+            "  }",
+            "}")
+        .doTest();
+  }
 }