[clangd] Deduplicate scopes in IncludeFixer queries

[sammccall]

clang-tools-extra/clangd/IncludeFixer.cpp

316–317

nit: sort+erase-unique is probably cheaper than constructing a set and then copying it

(probably not a huge deal but we do this for each typo I think)

[kadircet]

• sort+unique+erase instead of using a set
• Inline visitor and directly collect scopes there.

[kadircet]

• add back the global scope.

clang-tools-extra/clangd/IncludeFixer.cpp

 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <algorithm>
+#include <set>
+#include <string>
 #include <vector>
 
 namespace clang {
 namespace clangd {
 
-namespace {
-
-// Collects contexts visited during a Sema name lookup.
-class VisitedContextCollector : public VisibleDeclConsumer {
-public:
-  void EnteredContext(DeclContext *Ctx) override { Visited.push_back(Ctx); }
-
-  void FoundDecl(NamedDecl *ND, NamedDecl *Hiding, DeclContext *Ctx,
-                 bool InBaseClass) override {}
-
-  std::vector<DeclContext *> takeVisitedContexts() {
-    return std::move(Visited);
-  }
-
-private:
-  std::vector<DeclContext *> Visited;
-};
-
-} // namespace
-
 std::vector<Fix> IncludeFixer::fix(DiagnosticsEngine::Level DiagLevel,
                                    const clang::Diagnostic &Info) const {
   switch (Info.getID()) {
   case diag::err_incomplete_nested_name_spec:
   case diag::err_incomplete_base_class:
   case diag::err_incomplete_member_access:
   case diag::err_incomplete_type:
   case diag::err_typecheck_decl_incomplete_type:
llvm::Optional<CheapUnresolvedName> extractUnresolvedNameCheaply(
   }
   return Result;
 }
 
 /// Returns all namespace scopes that the unqualified lookup would visit.
 std::vector<std::string>
 collectAccessibleScopes(Sema &Sem, const DeclarationNameInfo &Typo, Scope *S,
                         Sema::LookupNameKind LookupKind) {
+  // Collects contexts visited during a Sema name lookup.
+  struct VisitedContextCollector : public VisibleDeclConsumer {
+    VisitedContextCollector(std::vector<std::string> &Out) : Out(Out) {}
+    void EnteredContext(DeclContext *Ctx) override {
+      if (llvm::isa<NamespaceDecl>(Ctx))
+        Out.push_back(printNamespaceScope(*Ctx));
+    }
+    void FoundDecl(NamedDecl *ND, NamedDecl *Hiding, DeclContext *Ctx,
+                   bool InBaseClass) override {}
+    std::vector<std::string> &Out;
+  };
+
   std::vector<std::string> Scopes;
-  VisitedContextCollector Collector;
+  Scopes.push_back("");
+  VisitedContextCollector Collector(Scopes);
   Sem.LookupVisibleDecls(S, LookupKind, Collector,
                          /*IncludeGlobalScope=*/false,
                          /*LoadExternal=*/false);
-
-  Scopes.push_back("");
-  for (const auto *Ctx : Collector.takeVisitedContexts()) {
-    if (isa<NamespaceDecl>(Ctx))
-      Scopes.push_back(printNamespaceScope(*Ctx));
-  }
+  std::sort(Scopes.begin(), Scopes.end());
+  Scopes.erase(std::unique(Scopes.begin(), Scopes.end()), Scopes.end());
   return Scopes;
 }
 
 class IncludeFixer::UnresolvedNameRecorder : public ExternalSemaSource {
 public:
   UnresolvedNameRecorder(llvm::Optional<UnresolvedName> &LastUnresolvedName)
       : LastUnresolvedName(LastUnresolvedName) {}