Don't try to convert recursive lambdas to methods

In principle this is possible to get right, but it's a lot of work for a very rare code pattern. Instead, just give up on it. PiperOrigin-RevId: 449810510
google · May 19, 2022 · 9ff2d42 · 9ff2d42
1 parent 85f55f2
commit 9ff2d42
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diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java b/core/src/main/java/com/google/errorprone/bugpatterns/UnnecessaryLambda.java
@@ -190,13 +190,34 @@ private boolean canFix(Tree type, Symbol sym, VisitorState state) {
     class Scanner extends TreePathScanner<Void, Void> {
 
       boolean fixable = true;
+      boolean inInitializer = false;
 
       @Override
       public Void visitMethodInvocation(MethodInvocationTree node, Void unused) {
         check(node);
         return super.visitMethodInvocation(node, null);
       }
 
+      @Override
+      public Void visitVariable(VariableTree node, Void unused) {
+        boolean wasInInitializer = inInitializer;
+        if (sym.equals(getSymbol(node))) {
+          inInitializer = true;
+        }
+        super.visitVariable(node, null);
+        inInitializer = wasInInitializer;
+        return null;
+      }
+
+      @Override
+      public Void visitMemberSelect(MemberSelectTree node, Void unused) {
+        if (inInitializer && sym.equals(getSymbol(node))) {
+          // We're not smart enough to rewrite a recursive lambda.
+          fixable = false;
+        }
+        return super.visitMemberSelect(node, unused);
+      }
+
       private void check(MethodInvocationTree node) {
         ExpressionTree lhs = node.getMethodSelect();
         if (!(lhs instanceof MemberSelectTree)) {

diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/UnnecessaryLambdaTest.java
@@ -316,4 +316,17 @@ public void variable_notAFunctionalInterface() {
         .expectUnchanged()
         .doTest();
   }
+
+  @Test
+  public void recursiveLambda_ignored() {
+    testHelper
+        .addInputLines(
+            "Test.java",
+            "import java.util.function.Predicate;",
+            "class Test {",
+            "  private static final Predicate<String> F = x -> Test.F.test(x);",
+            "}")
+        .expectUnchanged()
+        .doTest();
+  }
 }