[clang] [clang][ASTImporter] delay import funtion return type (PR #74991)

[Qizhi Hu via cfe-commits]

https://github.com/jcsxky updated https://github.com/llvm/llvm-project/pull/74991

>From 8dc4955fad0147db16bddfe8fc7d227ae69b89a1 Mon Sep 17 00:00:00 2001
From: huqizhi <huqizhi at feysh.com>
Date: Sun, 10 Dec 2023 21:01:49 +0800
Subject: [PATCH] [clang][ASTImporter] add processing of
 SubstNonTypeTemplateParmExpr in isAncestorDeclContextOf

---
 clang/lib/AST/ASTImporter.cpp           | 15 ++++++++++-----
 clang/unittests/AST/ASTImporterTest.cpp | 20 ++++++++++++++++++++
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index f1f335118f37a4..8f360e9443011f 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -3418,10 +3418,15 @@ static bool isAncestorDeclContextOf(const DeclContext *DC, const Stmt *S) {
   while (!ToProcess.empty()) {
     const Stmt *CurrentS = ToProcess.pop_back_val();
     ToProcess.append(CurrentS->child_begin(), CurrentS->child_end());
-    if (const auto *DeclRef = dyn_cast<DeclRefExpr>(CurrentS))
+    if (const auto *DeclRef = dyn_cast<DeclRefExpr>(CurrentS)) {
       if (const Decl *D = DeclRef->getDecl())
         if (isAncestorDeclContextOf(DC, D))
           return true;
+    } else if (const auto *E =
+                   dyn_cast_or_null<SubstNonTypeTemplateParmExpr>(CurrentS)) {
+      if (isAncestorDeclContextOf(DC, E->getAssociatedDecl()))
+        return true;
+    }
   }
   return false;
 }
@@ -3745,15 +3750,15 @@ 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)) {
-      FromReturnTy = Importer.getFromContext().VoidTy;
-      UsedDifferentProtoType = true;
-    }
     FunctionProtoType::ExtProtoInfo FromEPI = FromFPT->getExtProtoInfo();
     // FunctionProtoType::ExtProtoInfo's ExceptionSpecDecl can point to the
     // FunctionDecl that we are importing the FunctionProtoType for.
     // To avoid an infinite recursion when importing, create the FunctionDecl
     // with a simplified function type.
+    if (hasAutoReturnTypeDeclaredInside(D)) {
+      FromReturnTy = Importer.getFromContext().VoidTy;
+      UsedDifferentProtoType = true;
+    }
     if (FromEPI.ExceptionSpec.SourceDecl ||
         FromEPI.ExceptionSpec.SourceTemplate ||
         FromEPI.ExceptionSpec.NoexceptExpr) {
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
index 4dd7510bf8ddf8..7ab9db4251e80b 100644
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -9284,6 +9284,26 @@ TEST_P(ASTImporterOptionSpecificTestBase,
   // EXPECT_EQ(ToF1Imported->getPreviousDecl(), ToF1);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase, ImportFunctionAutoType) {
+  const char *Code =
+      R"(
+      template<int>
+      struct array {};
+
+      template <int N>
+      auto foo() { return array<N>(); }
+
+      void bar() { foo<0>(); }
+      )";
+  Decl *FromTU = getTuDecl(Code, Lang_CXX17);
+
+  auto *FromBar = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("bar")));
+
+  auto *ToBar = Import(FromBar, Lang_CXX17);
+  EXPECT_TRUE(ToBar);
+}
+
 INSTANTIATE_TEST_SUITE_P(ParameterizedTests, ASTImporterLookupTableTest,
                          DefaultTestValuesForRunOptions);