[clang][ASTImporter] Add support for importing CXXFoldExpr.

Reviewed By: shafik, martong

Differential Revision: https://reviews.llvm.org/D94786

Author: balazske

clang/lib/AST/ASTImporter.cpp

@@ -644,6 +644,7 @@ namespace clang {
     ExpectedStmt VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E);
     ExpectedStmt VisitTypeTraitExpr(TypeTraitExpr *E);
     ExpectedStmt VisitCXXTypeidExpr(CXXTypeidExpr *E);
+    ExpectedStmt VisitCXXFoldExpr(CXXFoldExpr *E);
 
     template<typename IIter, typename OIter>
     Error ImportArrayChecked(IIter Ibegin, IIter Iend, OIter Obegin) {
@@ -8011,6 +8012,25 @@ ExpectedStmt ASTNodeImporter::VisitCXXTypeidExpr(CXXTypeidExpr *E) {
       *ToTypeOrErr, *ToExprOperandOrErr, *ToSourceRangeOrErr);
 }
 
+ExpectedStmt ASTNodeImporter::VisitCXXFoldExpr(CXXFoldExpr *E) {
+  Error Err = Error::success();
+
+  QualType ToType = importChecked(Err, E->getType());
+  UnresolvedLookupExpr *ToCallee = importChecked(Err, E->getCallee());
+  SourceLocation ToLParenLoc = importChecked(Err, E->getLParenLoc());
+  Expr *ToLHS = importChecked(Err, E->getLHS());
+  SourceLocation ToEllipsisLoc = importChecked(Err, E->getEllipsisLoc());
+  Expr *ToRHS = importChecked(Err, E->getRHS());
+  SourceLocation ToRParenLoc = importChecked(Err, E->getRParenLoc());
+
+  if (Err)
+    return std::move(Err);
+
+  return new (Importer.getToContext())
+      CXXFoldExpr(ToType, ToCallee, ToLParenLoc, ToLHS, E->getOperator(),
+                  ToEllipsisLoc, ToRHS, ToRParenLoc, E->getNumExpansions());
+}
+
 Error ASTNodeImporter::ImportOverriddenMethods(CXXMethodDecl *ToMethod,
                                                CXXMethodDecl *FromMethod) {
   Error ImportErrors = Error::success();

clang/unittests/AST/ASTImporterTest.cpp

@@ -639,6 +639,38 @@ TEST_P(ImportExpr, ImportSizeOfPackExpr) {
           hasUnqualifiedDesugaredType(constantArrayType(hasSize(7))))))))));
 }
 
+const internal::VariadicDynCastAllOfMatcher<Stmt, CXXFoldExpr> cxxFoldExpr;
+
+AST_MATCHER_P(CXXFoldExpr, hasOperator, BinaryOperatorKind, Op) {
+  return Node.getOperator() == Op;
+}
+AST_MATCHER(CXXFoldExpr, hasInit) { return Node.getInit(); }
+AST_MATCHER(CXXFoldExpr, isRightFold) { return Node.isRightFold(); }
+AST_MATCHER(CXXFoldExpr, isLeftFold) { return Node.isLeftFold(); }
+
+TEST_P(ImportExpr, ImportCXXFoldExpr) {
+  auto Match1 =
+      cxxFoldExpr(hasOperator(BO_Add), isLeftFold(), unless(hasInit()));
+  auto Match2 = cxxFoldExpr(hasOperator(BO_Sub), isLeftFold(), hasInit());
+  auto Match3 =
+      cxxFoldExpr(hasOperator(BO_Mul), isRightFold(), unless(hasInit()));
+  auto Match4 = cxxFoldExpr(hasOperator(BO_Div), isRightFold(), hasInit());
+
+  MatchVerifier<Decl> Verifier;
+  testImport("template <typename... Ts>"
+             "void declToImport(Ts... args) {"
+             "  const int i1 = (... + args);"
+             "  const int i2 = (1 - ... - args);"
+             "  const int i3 = (args * ...);"
+             "  const int i4 = (args / ... / 1);"
+             "};"
+             "void g() { declToImport(1, 2, 3, 4, 5); }",
+             Lang_CXX17, "", Lang_CXX17, Verifier,
+             functionTemplateDecl(hasDescendant(Match1), hasDescendant(Match2),
+                                  hasDescendant(Match3),
+                                  hasDescendant(Match4)));
+}
+
 /// \brief Matches __builtin_types_compatible_p:
 /// GNU extension to check equivalent types
 /// Given