[clang] [ASTImporter] Fix infinite recurse on return type declared inside body (#68775) (PR #89096)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Ding Fei (danix800)

<details>
<summary>Changes</summary>

Lambda without trailing auto could has return type declared inside the body too.

---
Full diff: https://github.com/llvm/llvm-project/pull/89096.diff


2 Files Affected:

- (modified) clang/lib/AST/ASTImporter.cpp (+6-10) 
- (modified) clang/unittests/AST/ASTImporterTest.cpp (+16) 


``````````diff
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 6aaa34c55ce307..88883bbd6ebaf1 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -695,7 +695,7 @@ namespace clang {
     // Returns true if the given function has a placeholder return type and
     // that type is declared inside the body of the function.
     // E.g. auto f() { struct X{}; return X(); }
-    bool hasAutoReturnTypeDeclaredInside(FunctionDecl *D);
+    bool hasReturnTypeDeclaredInside(FunctionDecl *D);
   };
 
 template <typename InContainerTy>
@@ -3649,19 +3649,15 @@ class IsTypeDeclaredInsideVisitor
 
 /// This function checks if the function has 'auto' return type that contains
 /// a reference (in any way) to a declaration inside the same function.
-bool ASTNodeImporter::hasAutoReturnTypeDeclaredInside(FunctionDecl *D) {
+bool ASTNodeImporter::hasReturnTypeDeclaredInside(FunctionDecl *D) {
   QualType FromTy = D->getType();
   const auto *FromFPT = FromTy->getAs<FunctionProtoType>();
   assert(FromFPT && "Must be called on FunctionProtoType");
 
   QualType RetT = FromFPT->getReturnType();
-  if (isa<AutoType>(RetT.getTypePtr())) {
-    FunctionDecl *Def = D->getDefinition();
-    IsTypeDeclaredInsideVisitor Visitor(Def ? Def : D);
-    return Visitor.CheckType(RetT);
-  }
-
-  return false;
+  FunctionDecl *Def = D->getDefinition();
+  IsTypeDeclaredInsideVisitor Visitor(Def ? Def : D);
+  return Visitor.CheckType(RetT);
 }
 
 ExplicitSpecifier
@@ -3811,7 +3807,7 @@ ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
     // E.g.: auto foo() { struct X{}; return X(); }
     // To avoid an infinite recursion when importing, create the FunctionDecl
     // with a simplified return type.
-    if (hasAutoReturnTypeDeclaredInside(D)) {
+    if (hasReturnTypeDeclaredInside(D)) {
       FromReturnTy = Importer.getFromContext().VoidTy;
       UsedDifferentProtoType = true;
     }
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
index acc596fef87b76..3fac5514319c24 100644
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -6721,6 +6721,22 @@ TEST_P(ASTImporterOptionSpecificTestBase, LambdaInFunctionBody) {
   EXPECT_FALSE(FromL->isDependentLambda());
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, LambdaReturnTypeDeclaredInside) {
+  Decl *From, *To;
+  std::tie(From, To) = getImportedDecl(
+      R"(
+      void foo() {
+        (void) []() {
+          struct X {};
+          return X();
+        };
+      }
+      )",
+      Lang_CXX11, "", Lang_CXX11, "foo");
+  auto *ToLambda = FirstDeclMatcher<LambdaExpr>().match(To, lambdaExpr());
+  EXPECT_TRUE(ToLambda);
+}
+
 TEST_P(ASTImporterOptionSpecificTestBase, LambdaInFunctionParam) {
   Decl *FromTU = getTuDecl(
       R"(

``````````

</details>


https://github.com/llvm/llvm-project/pull/89096