[lldb][test] Add tests for clang::PreferredNameAttr formatting

[Michael137]

Summary

Add some tests to make sure we're formatting structures
with preferred names correctly.

[Michael137]

• Update testcase

lldb/test/API/lang/cpp/preferred_name/Makefile

+CXX_SOURCES := main.cpp
+CXXFLAGS_EXTRAS := -std=c++20 -glldb
+include Makefile.rules

lldb/test/API/lang/cpp/preferred_name/TestPreferredName.py

+"""
+Test formatting of types annotated with
+[[clang::preferred_name]] attributes.
+"""
+
+import lldb
+import lldbsuite.test.lldbutil as lldbutil
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import decorators
+
+
+class TestPreferredName(TestBase):
+
+    def test_frame_var(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "return", lldb.SBFileSpec("main.cpp"))
+
+        self.expect("frame variable barInt", substrs=["BarInt"])
+        self.expect("frame variable barDouble", substrs=["BarDouble"])
+        self.expect("frame variable barShort", substrs=["Bar<short>"])
+        self.expect("frame variable barChar", substrs=["Bar<char>"])
+
+        self.expect("frame variable varInt", substrs=["BarInt"])
+        self.expect("frame variable varDouble", substrs=["BarDouble"])
+        self.expect("frame variable varShort", substrs=["Bar<short>"])
+        self.expect("frame variable varChar", substrs=["Bar<char>"])
+
+    def test_expr(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "return", lldb.SBFileSpec("main.cpp"))
+
+        self.expect_expr("barInt", result_type="BarInt")
+        self.expect_expr("barDouble", result_type="BarDouble")
+        self.expect_expr("barShort", result_type="Bar<short>")
+        self.expect_expr("barChar", result_type="Bar<char>")
+
+        self.expect_expr("varInt", result_type="BarInt")
+        self.expect_expr("varDouble", result_type="BarDouble")
+        self.expect_expr("varShort", result_type="Bar<short>")
+        self.expect_expr("varChar", result_type="Bar<char>")

lldb/test/API/lang/cpp/preferred_name/main.cpp

+template <typename T> struct Foo;
+
+typedef Foo<int> BarInt;
+typedef Foo<double> BarDouble;
+
+template <typename T> using Bar = Foo<T>;
+
+template <typename T>
+struct [[clang::preferred_name(BarInt), clang::preferred_name(BarDouble),
+         clang::preferred_name(Bar<short>), clang::preferred_name(Bar<short>),
+         clang::preferred_name(Bar<double>),
+         clang::preferred_name(Bar<char>)]] Foo{};
+
+int main() {
+  BarInt barInt;
+  BarDouble barDouble;
+  Bar<short> barShort;
+  Bar<char> barChar;
+
+  Foo<int> varInt;
+  Foo<double> varDouble;
+  Foo<short> varShort;
+  Foo<char> varChar;
+  return 0;
+}