[lldb] Add DebugDescription test (NFC)

lldb/test/API/lang/swift/debugdescriptionmacro/Makefile

@@ -0,0 +1,3 @@
+SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS := -enable-experimental-feature SymbolLinkageMarkers
+include Makefile.rules

lldb/test/API/lang/swift/debugdescriptionmacro/TestDebugDescriptionMacro.py

@@ -0,0 +1,17 @@
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestCase(TestBase):
+    @swiftTest
+    def test(self):
+        "docstring"
+        self.build()
+        _, _, thread, _ = lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.swift")
+        )
+        frame = thread.frames[0]
+        unit = frame.FindVariable("unit")
+        self.assertEqual(unit.summary, '"fulfilled"')

lldb/test/API/lang/swift/debugdescriptionmacro/main.swift

@@ -0,0 +1,11 @@
+@_DebugDescription
+struct Unit {
+  var description: String { "fulfilled" }
+}
+
+func main() {
+  let unit = Unit()
+  print("break here", unit)
+}
+
+main()