[lldb] Allow evaluating expressions in C++20 mode

This patch allows users to evaluate expressions using
`expr -l c++20`. Currently DWARF keeps the CU's at
`DW_AT_language` at `DW_LANG_C_plus_plus_14` even
when compiling with `-std=c++20`. So even in "C++20
programs" expression evaluation will by default be
performed in `C++11` mode for now.

Enabling `C++14` has been previously attempted at
https://reviews.llvm.org/D80308

There are some remaining issues around evaluating C++20
expressions. Mainly, lack of support for C++20 AST nodes in
`clang::ASTImporter`. But these can be addressed in follow-up
patches.

1 files changed, 7 insertions, 5 deletions

diff --git a/lldb/unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp b/lldb/unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp
index 6c85ed159df5..cfdc3163f6a3 100644
--- a/lldb/unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp
+++ b/lldb/unittests/Language/CPlusPlus/CPlusPlusLanguageTest.cpp
@@ -205,7 +205,11 @@ TEST(CPlusPlusLanguage, MethodNameParsing) {
 
       {"auto Foo[abi:abc]<int>::operator<<<Foo[abi:abc]<int>>(int) &", "auto",
        "Foo[abi:abc]<int>", "operator<<<Foo[abi:abc]<int>>", "(int)", "&",
-       "Foo[abi:abc]<int>::operator<<<Foo[abi:abc]<int>>"}};
+       "Foo[abi:abc]<int>::operator<<<Foo[abi:abc]<int>>"},
+
+      {"auto A::operator<=>[abi:tag]<A::B>()", "auto", "A",
+       "operator<=>[abi:tag]<A::B>", "()", "",
+       "A::operator<=>[abi:tag]<A::B>"}};
 
   for (const auto &test : test_cases) {
     CPlusPlusLanguage::MethodName method(ConstString(test.input));
@@ -227,7 +231,6 @@ TEST(CPlusPlusLanguage, InvalidMethodNameParsing) {
   std::string test_cases[] = {
       "int Foo::operator[]<[10>()",
       "Foo::operator bool[10]()",
-      "auto A::operator<=>[abi:tag]<A::B>()",
       "auto A::operator<<<(int)",
       "auto A::operator>>>(int)",
       "auto A::operator<<<Type[abi:tag]<>(int)",
@@ -356,10 +359,9 @@ TEST(CPlusPlusLanguage, ExtractContextAndIdentifier) {
   EXPECT_FALSE(CPlusPlusLanguage::ExtractContextAndIdentifier(
       "f<A<B><C>>", context, basename));
 
-  // We expect these cases to fail until we turn on C++2a
-  EXPECT_FALSE(CPlusPlusLanguage::ExtractContextAndIdentifier(
+  EXPECT_TRUE(CPlusPlusLanguage::ExtractContextAndIdentifier(
       "A::operator<=><A::B>", context, basename));
-  EXPECT_FALSE(CPlusPlusLanguage::ExtractContextAndIdentifier(
+  EXPECT_TRUE(CPlusPlusLanguage::ExtractContextAndIdentifier(
       "operator<=><A::B>", context, basename));
 }