From e82c86b00c49433ccc847f050e1be199194638bc Mon Sep 17 00:00:00 2001
From: Liam Miller-Cushon <cushon@google.com>
Date: Fri, 15 Sep 2023 11:14:33 -0700
Subject: [PATCH] Skip UnnecessaryLambda findings for usages in enhanced for
 loops

https://github.com/google/error-prone/issues/2518

PiperOrigin-RevId: 565728375
---
 .../bugpatterns/UnnecessaryLambda.java        | 14 +++++++++++-
 .../bugpatterns/UnnecessaryLambdaTest.java    | 22 +++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java b/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java
index be9332b94798..1cad68ba1216 100644
--- a/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java
@@ -43,6 +43,7 @@
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.BlockTree;
+import com.sun.source.tree.EnhancedForLoopTree;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.IdentifierTree;
 import com.sun.source.tree.LambdaExpressionTree;
@@ -101,15 +102,26 @@ public Description matchMethod(MethodTree tree, VisitorState state) {
     if (state.isAndroidCompatible()) {
       return NO_MATCH;
     }
+    boolean[] usedInEnhancedForLoop = {false};
     new TreePathScanner<Void, Void>() {
       @Override
       public Void visitMethodInvocation(MethodInvocationTree node, Void unused) {
+
         if (Objects.equals(getSymbol(node), sym)) {
-          replaceUseWithMethodReference(fix, node, name, state.withPath(getCurrentPath()));
+          Tree parent = getCurrentPath().getParentPath().getLeaf();
+          if (parent instanceof EnhancedForLoopTree
+              && ((EnhancedForLoopTree) parent).getExpression().equals(node)) {
+            usedInEnhancedForLoop[0] = true;
+          } else {
+            replaceUseWithMethodReference(fix, node, name, state.withPath(getCurrentPath()));
+          }
         }
         return super.visitMethodInvocation(node, null);
       }
     }.scan(state.getPath().getCompilationUnit(), null);
+    if (usedInEnhancedForLoop[0]) {
+      return NO_MATCH;
+    }
     lambdaToMethod(state, lambda, fix, name, type);
     return describeMatch(tree, fix.build());
   }
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java
index 69e16564851b..f80bb0eb527a 100644
--- a/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java
@@ -388,4 +388,26 @@ public void e() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void iterable() {
+    testHelper
+        .addInputLines(
+            "Test.java",
+            "import java.util.stream.IntStream;",
+            "import java.util.ArrayList;",
+            "import java.util.stream.IntStream;",
+            "class Example {",
+            "  void someLoopyCode() {",
+            "    for (int i : someIterable()) {",
+            "      // Do something.",
+            "    }",
+            "  }",
+            "  private Iterable<Integer> someIterable() {",
+            "    return () -> IntStream.range(0, 42).boxed().iterator();",
+            "  }",
+            "}")
+        .expectUnchanged()
+        .doTest();
+  }
 }