From 3d0a2d92576cd24a72774f4e39c0c6317e8e1686 Mon Sep 17 00:00:00 2001
From: Justin Buchanan <justinbuchanan@google.com>
Date: Thu, 12 Oct 2023 11:09:25 -0700
Subject: [PATCH] fix(cxx): use correct definition anchor spans for lambdas
 (#5890)

---
 kythe/cxx/indexer/cxx/IndexerASTHooks.cc       | 17 ++++++++++++++---
 kythe/cxx/indexer/cxx/testdata/BUILD           |  1 +
 kythe/cxx/indexer/cxx/testdata/basic/lambda.cc | 16 +++++++++++++---
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/kythe/cxx/indexer/cxx/IndexerASTHooks.cc b/kythe/cxx/indexer/cxx/IndexerASTHooks.cc
index 7859cd8b88..d1b4ff5634 100644
--- a/kythe/cxx/indexer/cxx/IndexerASTHooks.cc
+++ b/kythe/cxx/indexer/cxx/IndexerASTHooks.cc
@@ -3469,10 +3469,21 @@ bool IndexerASTVisitor::VisitFunctionDecl(clang::FunctionDecl* Decl) {
 
   if (IsFunctionDefinition && !Decl->isImplicit() &&
       Decl->getBody() != nullptr) {
+    // For lambdas, Decl does not contain the correct SourceRange directly.
+    // Instead, we look at the "synthesized" lambda class and use it's beginning
+    // location as the start of the source range.
+    clang::SourceRange Range = Decl->getSourceRange();
+    if (clang::CXXMethodDecl* MethodDecl =
+            llvm::dyn_cast<clang::CXXMethodDecl>(Decl)) {
+      const clang::CXXRecordDecl* Parent = MethodDecl->getParent();
+      if (Parent->isLambda()) {
+        Range.setBegin(Parent->getSourceRange().getBegin());
+      }
+    }
+
     SourceRange DefinitionRange = NormalizeRange(
-        {TemplateKeywordLoc.isValid() ? TemplateKeywordLoc
-                                      : Decl->getSourceRange().getBegin(),
-         Decl->getSourceRange().getEnd()});
+        {TemplateKeywordLoc.isValid() ? TemplateKeywordLoc : Range.getBegin(),
+         Range.getEnd()});
     auto DefinitionRangeInContext =
         RangeInCurrentContext(Decl->isImplicit(), DeclNode, DefinitionRange);
     MaybeRecordFullDefinitionRange(DefinitionRangeInContext, DeclNode,
diff --git a/kythe/cxx/indexer/cxx/testdata/BUILD b/kythe/cxx/indexer/cxx/testdata/BUILD
index 416e9e210d..bfd80aade6 100644
--- a/kythe/cxx/indexer/cxx/testdata/BUILD
+++ b/kythe/cxx/indexer/cxx/testdata/BUILD
@@ -962,6 +962,7 @@ cc_indexer_test(
 cc_indexer_test(
     name = "lambda_test",
     srcs = ["basic/lambda.cc"],
+    ignore_dups = True,
     tags = ["basic"],
 )
 
diff --git a/kythe/cxx/indexer/cxx/testdata/basic/lambda.cc b/kythe/cxx/indexer/cxx/testdata/basic/lambda.cc
index 13b9874bcc..8b298417c8 100644
--- a/kythe/cxx/indexer/cxx/testdata/basic/lambda.cc
+++ b/kythe/cxx/indexer/cxx/testdata/basic/lambda.cc
@@ -1,4 +1,14 @@
-// TODO(justinbuchanan): fix indexer to include leading '[](' in lambda anchor
-//- @") {}" defines Lambda
-//- Lambda.node/kind function
+//- @"[]() {}" defines LambdaFn
+//- LambdaFn.node/kind function
 auto fn = []() {};
+
+//- @"[]() -> int { return 0; }" defines LambdaFn2
+//- LambdaFn2.node/kind function
+auto fn2 = []() -> int { return 0; };
+
+void outer() {
+  int i = 0;
+  //- @"[&i]() {}" defines LambdaFn3
+  //- LambdaFn3.node/kind function
+  auto fn3 = [&i]() {};
+}