[clang][ASTImporter] Fix for importing functions with EST_Unevaluated…

… prototype.

Fix for importing functions where the TypeSourceInfo is set and the
exception specification information contains reference to the function
declaration itself.

Reviewed By: martong, steakhal

Differential Revision: https://reviews.llvm.org/D112013

clang/lib/AST/ASTImporter.cpp

@@ -3422,11 +3422,14 @@ ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
     return std::move(Err);
 
   QualType FromTy = D->getType();
+  TypeSourceInfo *FromTSI = D->getTypeSourceInfo();
   // Set to true if we do not import the type of the function as is. There are
   // cases when the original type would result in an infinite recursion during
   // the import. To avoid an infinite recursion when importing, we create the
   // FunctionDecl with a simplified function type and update it only after the
   // relevant AST nodes are already imported.
+  // The type is related to TypeSourceInfo (it references the type), so we must
+  // do the same with TypeSourceInfo.
   bool UsedDifferentProtoType = false;
   if (const auto *FromFPT = FromTy->getAs<FunctionProtoType>()) {
     QualType FromReturnTy = FromFPT->getReturnType();
@@ -3453,11 +3456,13 @@ ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
     }
     FromTy = Importer.getFromContext().getFunctionType(
         FromReturnTy, FromFPT->getParamTypes(), FromEPI);
+    FromTSI = Importer.getFromContext().getTrivialTypeSourceInfo(
+        FromTy, D->getBeginLoc());
   }
 
   Error Err = Error::success();
   auto T = importChecked(Err, FromTy);
-  auto TInfo = importChecked(Err, D->getTypeSourceInfo());
+  auto TInfo = importChecked(Err, FromTSI);
   auto ToInnerLocStart = importChecked(Err, D->getInnerLocStart());
   auto ToEndLoc = importChecked(Err, D->getEndLoc());
   auto ToQualifierLoc = importChecked(Err, D->getQualifierLoc());
@@ -3635,6 +3640,10 @@ ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
       ToFunction->setType(*TyOrErr);
     else
       return TyOrErr.takeError();
+    if (Expected<TypeSourceInfo *> TSIOrErr = import(D->getTypeSourceInfo()))
+      ToFunction->setTypeSourceInfo(*TSIOrErr);
+    else
+      return TSIOrErr.takeError();
   }
 
   // FIXME: Other bits to merge?

clang/unittests/AST/ASTImporterTest.cpp

@@ -6145,6 +6145,50 @@ TEST_P(ASTImporterOptionSpecificTestBase, ImportDefaultConstructibleLambdas) {
             2u);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase,
+       ImportFunctionDeclWithTypeSourceInfoWithSourceDecl) {
+  // This code results in a lambda with implicit constructor.
+  // The constructor's TypeSourceInfo points out the function prototype.
+  // This prototype has an EST_Unevaluated in its exception information and a
+  // SourceDecl that is the function declaration itself.
+  // The test verifies that AST import of such AST does not crash.
+  // (Here the function's TypeSourceInfo references the function itself.)
+  Decl *FromTU = getTuDecl(
+      R"(
+        template<typename T> void f(T) { auto X = [](){}; }
+        void g() { f(10); }
+        )",
+      Lang_CXX11, "input0.cc");
+
+  // Use LastDeclMatcher to find the LambdaExpr in the template specialization.
+  CXXRecordDecl *FromL = LastDeclMatcher<LambdaExpr>()
+                             .match(FromTU, lambdaExpr())
+                             ->getLambdaClass();
+
+  CXXConstructorDecl *FromCtor = *FromL->ctor_begin();
+  ASSERT_TRUE(FromCtor->isCopyConstructor());
+  ASSERT_TRUE(FromCtor->getTypeSourceInfo());
+  const auto *FromFPT = FromCtor->getType()->getAs<FunctionProtoType>();
+  ASSERT_TRUE(FromFPT);
+  EXPECT_EQ(FromCtor->getTypeSourceInfo()->getType().getTypePtr(), FromFPT);
+  FunctionProtoType::ExtProtoInfo FromEPI = FromFPT->getExtProtoInfo();
+  // If type is EST_Unevaluated, SourceDecl should be set to the parent Decl.
+  EXPECT_EQ(FromEPI.ExceptionSpec.Type, EST_Unevaluated);
+  EXPECT_EQ(FromEPI.ExceptionSpec.SourceDecl, FromCtor);
+
+  auto ToL = Import(FromL, Lang_CXX11);
+
+  // Check if the import was correct.
+  CXXConstructorDecl *ToCtor = *ToL->ctor_begin();
+  EXPECT_TRUE(ToCtor->getTypeSourceInfo());
+  const auto *ToFPT = ToCtor->getType()->getAs<FunctionProtoType>();
+  ASSERT_TRUE(ToFPT);
+  EXPECT_EQ(ToCtor->getTypeSourceInfo()->getType().getTypePtr(), ToFPT);
+  FunctionProtoType::ExtProtoInfo ToEPI = ToFPT->getExtProtoInfo();
+  EXPECT_EQ(ToEPI.ExceptionSpec.Type, EST_Unevaluated);
+  EXPECT_EQ(ToEPI.ExceptionSpec.SourceDecl, ToCtor);
+}
+
 struct ImportAutoFunctions : ASTImporterOptionSpecificTestBase {};
 
 TEST_P(ImportAutoFunctions, ReturnWithTypedefDeclaredInside) {