[clangd] Handle destructors in DefineOutline tweak

Fix destructors being incorrectly defined in the DefineOutline tweak
Currently it doesn't prepend the class name to the destructor
```lang=c++
class A { ~A() {} };
// Destructor definition after outline
~A() {}
// After this fix
A::~A() {}
```

Reviewed By: kadircet

Differential Revision: https://reviews.llvm.org/D147802

Author: njames93

clang-tools-extra/clangd/refactor/tweaks/DefineOutline.cpp

@@ -183,6 +183,20 @@ getFunctionSourceCode(const FunctionDecl *FD, llvm::StringRef TargetNamespace,
       },
       Resolver);
 
+  // findExplicitReferences doesn't provide references to
+  // constructor/destructors, it only provides references to type names inside
+  // them.
+  // this works for constructors, but doesn't work for destructor as type name
+  // doesn't cover leading `~`, so handle it specially.
+  if (const auto *Destructor = llvm::dyn_cast<CXXDestructorDecl>(FD)) {
+    if (auto Err = DeclarationCleanups.add(tooling::Replacement(
+            SM, Destructor->getLocation(), 0,
+            getQualification(AST, *TargetContext,
+                             SM.getLocForStartOfFile(SM.getMainFileID()),
+                             Destructor))))
+      Errors = llvm::joinErrors(std::move(Errors), std::move(Err));
+  }
+
   // Get rid of default arguments, since they should not be specified in
   // out-of-line definition.
   for (const auto *PVD : FD->parameters()) {

clang-tools-extra/clangd/unittests/tweaks/DefineOutlineTests.cpp

@@ -319,6 +319,12 @@ TEST_F(DefineOutlineTest, ApplyTest) {
             };)cpp",
           "  Foo::Foo(int) {}\n",
       },
+      // Destrctors
+      {
+          "class A { ~A^(){} };",
+          "class A { ~A(); };",
+          "A::~A(){} ",
+      },
   };
   for (const auto &Case : Cases) {
     SCOPED_TRACE(Case.Test);
@@ -532,6 +538,18 @@ TEST_F(DefineOutlineTest, QualifyFunctionName) {
           // account. This can be spelled as b::foo instead.
           "using namespace a;void a::b::foo() {} ",
       },
+      {
+          "namespace a { class A { ~A^(){} }; }",
+          "",
+          "namespace a { class A { ~A(); }; }",
+          "a::A::~A(){} ",
+      },
+      {
+          "namespace a { class A { ~A^(){} }; }",
+          "namespace a{}",
+          "namespace a { class A { ~A(); }; }",
+          "namespace a{A::~A(){} }",
+      },
   };
   llvm::StringMap<std::string> EditedFiles;
   for (auto &Case : Cases) {