[clang] [clang][ASTImporter][test] Add test for importing explicit object parameter (PR #124305)

[Balázs Kéri via cfe-commits]

================
@@ -3441,13 +3441,33 @@ TEST_P(ASTImporterOptionSpecificTestBase, ImportParmVarDecl) {
   ASSERT_TRUE(FromVar);
   ASSERT_TRUE(FromVar->hasUninstantiatedDefaultArg());
   ASSERT_TRUE(FromVar->getUninstantiatedDefaultArg());
+  ASSERT_FALSE(FromVar->isExplicitObjectParameter());
 
   const auto *ToVar = Import(FromVar, Lang_CXX11);
   EXPECT_TRUE(ToVar);
   EXPECT_TRUE(ToVar->hasUninstantiatedDefaultArg());
   EXPECT_TRUE(ToVar->getUninstantiatedDefaultArg());
   EXPECT_NE(FromVar->getUninstantiatedDefaultArg(),
             ToVar->getUninstantiatedDefaultArg());
+  EXPECT_FALSE(ToVar->isExplicitObjectParameter());
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportParmVarDecl_Explicit) {
+  const auto *Code = R"(
+    struct Wrapper {
+      void func(this Wrapper) {}
+    };
+    )";
+  Decl *FromTU = getTuDecl(Code, Lang_CXX23);
+  auto *FromVar = FirstDeclMatcher<ParmVarDecl>().match(FromTU, parmVarDecl());
+  ASSERT_TRUE(FromVar);
+  ASSERT_TRUE(FromVar->isExplicitObjectParameter());
+
+  const auto *ToVar = Import(FromVar, Lang_CXX23);
+  EXPECT_TRUE(ToVar);
+  EXPECT_TRUE(ToVar->isExplicitObjectParameter());
+  EXPECT_EQ(ToVar->getExplicitObjectParamThisLoc(),
+            FromVar->getExplicitObjectParamThisLoc());
----------------
balazske wrote:

It looks not correct to copy a `SourceLocation` from the "from" into the "to" context. They have a different source manager instance. Function [ASTNodeImporter::ImportDefaultArgOfParmVarDecl](https://clang.llvm.org/doxygen/classclang_1_1ASTNodeImporter.html#af363fc3da4121fce19f9a96e9e0b64fa) is the place where this is done. Copy of `getExplicitObjectParamThisLoc` should be replaced with normal import.

https://github.com/llvm/llvm-project/pull/124305