Author: Sam McCall
Date: 2019-11-29T15:21:13+01:00
New Revision: 19daa21f841ad45290c923689ee3d25198651a4c

URL: 
https://github.com/llvm/llvm-project/commit/19daa21f841ad45290c923689ee3d25198651a4c
DIFF: 
https://github.com/llvm/llvm-project/commit/19daa21f841ad45290c923689ee3d25198651a4c.diff

LOG: [clangd] Rethink how SelectionTree deals with macros and #includes.

Summary:
The exclusive-claim model is successful at resolving conflicts over tokens
between parent/child or siblings. However claims at the spelled-token
level do the wrong thing for macro expansions, where siblings can be
equally associated with the macro invocation.
Moreover, any model that only uses the endpoints in a range can fail when
a macro invocation occurs inside the node.

To address this, we use the existing TokenBuffer in more depth.
Claims are expressed in terms of expanded tokens, so there is no need to worry
about macros, includes etc.

Once we know which expanded tokens were claimed, they are mapped onto
spelled tokens for hit-testing.
This mapping is fairly flexible, currently the handling of macros is
pretty simple (map macro args onto spellings, other macro expansions onto the
macro name token).
This mapping is in principle token-by-token for correctness (though
there's some batching for performance).

The aggregation of the selection enum is now more principled as we need to be
able to aggregate several hit-test results together.

For simplicity i removed the ability to determine selectedness of TUDecl.
(That was originally implemented in 90a5bf92ff97b1, but doesn't seem to be very
important or worth the complexity any longer).

The expandedTokens(SourceLocation) helper could be added locally, but seems to
make sense on TokenBuffer.

Fixes https://github.com/clangd/clangd/issues/202
Fixes https://github.com/clangd/clangd/issues/126

Reviewers: hokein

Subscribers: MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits, 
ilya-biryukov

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70512

Added: 
    

Modified: 
    clang-tools-extra/clangd/Selection.cpp
    clang-tools-extra/clangd/Selection.h
    clang-tools-extra/clangd/unittests/SelectionTests.cpp
    clang-tools-extra/clangd/unittests/TweakTests.cpp
    clang/include/clang/Tooling/Syntax/Tokens.h
    clang/lib/Tooling/Syntax/Tokens.cpp
    clang/unittests/Tooling/Syntax/TokensTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clangd/Selection.cpp 
b/clang-tools-extra/clangd/Selection.cpp
index 5b29b916b33c..54b182b3c706 100644
--- a/clang-tools-extra/clangd/Selection.cpp
+++ b/clang-tools-extra/clangd/Selection.cpp
@@ -34,95 +34,283 @@ namespace {
 using Node = SelectionTree::Node;
 using ast_type_traits::DynTypedNode;
 
-// Identifies which tokens are selected, and evaluates claims of source ranges
-// by AST nodes. Tokens may be claimed only once: first-come, first-served.
-class SelectedTokens {
+// An IntervalSet maintains a set of disjoint subranges of an array.
+//
+// Initially, it contains the entire array.
+//           [-----------------------------------------------------------]
+//
+// When a range is erased(), it will typically split the array in two.
+//  Claim:                     [--------------------]
+//  after:   [----------------]                      [-------------------]
+//
+// erase() returns the segments actually erased. Given the state above:
+//  Claim:          [---------------------------------------]
+//  Out:            [---------]                      [------]
+//  After:   [-----]                                         [-----------]
+//
+// It is used to track (expanded) tokens not yet associated with an AST node.
+// On traversing an AST node, its token range is erased from the unclaimed set.
+// The tokens actually removed are associated with that node, and hit-tested
+// against the selection to determine whether the node is selected.
+template <typename T>
+class IntervalSet {
+public:
+  IntervalSet(llvm::ArrayRef<T> Range) : UnclaimedRanges(&rangeLess) {
+    UnclaimedRanges.insert(Range);
+  }
+
+  // Removes the elements of Claim from the set, modifying or removing ranges
+  // that overlap it.
+  // Returns the continuous subranges of Claim that were actually removed.
+  llvm::SmallVector<llvm::ArrayRef<T>, 4> erase(llvm::ArrayRef<T> Claim) {
+    llvm::SmallVector<llvm::ArrayRef<T>, 4> Out;
+    if (Claim.empty())
+      return Out;
+    // equal_range finds overlapping ranges, because of how we chose <.
+    auto Overlap = UnclaimedRanges.equal_range(Claim);
+    if (Overlap.first == Overlap.second)
+      return Out;
+
+    // General case:
+    // Claim:                   [-----------------]
+    // UnclaimedRanges: [-A-] [-B-] [-C-] [-D-] [-E-] [-F-] [-G-]
+    // Overlap:               ^first                  ^second
+    // Ranges C and D are fully included. Ranges B and E must be trimmed.
+
+    // First, copy all overlapping ranges into the output.
+    auto OutFirst = Out.insert(Out.end(), Overlap.first, Overlap.second);
+    // If any of the overlapping ranges were sliced by the claim, split them:
+    //  - restrict the returned range to the claimed part
+    //  - save the unclaimed part so it can be reinserted
+    llvm::ArrayRef<T> RemainingHead, RemainingTail;
+    if (Claim.begin() > OutFirst->begin()) {
+      RemainingHead = {OutFirst->begin(), Claim.begin()};
+      *OutFirst = {Claim.begin(), OutFirst->end()};
+    }
+    if (Claim.end() < Out.back().end()) {
+      RemainingTail = {Claim.end(), Out.back().end()};
+      Out.back() = {Out.back().begin(), Claim.end()};
+    }
+
+    // Erase all the overlapping ranges (invalidating all iterators).
+    UnclaimedRanges.erase(Overlap.first, Overlap.second);
+    // Reinsert ranges that were merely trimmed.
+    if (!RemainingHead.empty())
+      UnclaimedRanges.insert(RemainingHead);
+    if (!RemainingTail.empty())
+      UnclaimedRanges.insert(RemainingTail);
+
+    return Out;
+  }
+
+private:
+  using TokenRange = llvm::ArrayRef<T>;
+  // Given that the ranges we insert are disjoint, there are several ways to
+  // legally define range < range.
+  // We choose to define it so overlapping ranges compare equal.
+  static bool rangeLess(llvm::ArrayRef<T> L, llvm::ArrayRef<T> R) {
+    return L.end() <= R.begin();
+  }
+
+  // Disjoint sorted unclaimed ranges of expanded tokens.
+  std::set<llvm::ArrayRef<T>, decltype(&rangeLess)> UnclaimedRanges;
+};
+
+// Sentinel value for the selectedness of a node where we've seen no tokens 
yet.
+// This resolves to Unselected if no tokens are ever seen.
+// But Unselected + Complete -> Partial, while NoTokens + Complete --> 
Complete.
+// This value is never exposed publicly.
+constexpr SelectionTree::Selection NoTokens =
+    static_cast<SelectionTree::Selection>(
+        static_cast<unsigned char>(SelectionTree::Complete + 1));
+
+// Nodes start with NoTokens, and then use this function to aggregate the
+// selectedness as more tokens are found.
+void update(SelectionTree::Selection &Result, SelectionTree::Selection New) {
+  if (New == NoTokens)
+    return;
+  if (Result == NoTokens)
+    Result = New;
+  else if (Result != New)
+    // Can only be completely selected (or unselected) if all tokens are.
+    Result = SelectionTree::Partial;
+}
+
+
+// SelectionTester can determine whether a range of tokens from the PP-expanded
+// stream (corresponding to an AST node) is considered selected.
+//
+// When the tokens result from macro expansions, the appropriate tokens in the
+// main file are examined (macro invocation or args). Similarly for #includes.
+//
+// It tests each token in the range (not just the endpoints) as contiguous
+// expanded tokens may not have contiguous spellings (with macros).
+//
+// Non-token text, and tokens not modeled in the AST (comments, semicolons)
+// are ignored when determining selectedness.
+class SelectionTester {
 public:
-  SelectedTokens(llvm::ArrayRef<syntax::Token> Spelled, const SourceManager 
&SM,
-                 unsigned SelBegin, unsigned SelEnd)
-      : SelBegin(SelBegin), SelEnd(SelEnd) {
-    // Extract bounds and selected-ness for all tokens spelled in the file.
-    Tokens.reserve(Spelled.size());
-    for (const auto& Tok : Spelled) {
+  // The selection is offsets [SelBegin, SelEnd) in SelFile.
+  SelectionTester(const syntax::TokenBuffer &Buf, FileID SelFile,
+                  unsigned SelBegin, unsigned SelEnd, const SourceManager &SM)
+      : SelFile(SelFile), SM(SM) {
+    // Find all tokens (partially) selected in the file.
+    auto AllSpelledTokens = Buf.spelledTokens(SelFile);
+    const syntax::Token *SelFirst =
+        llvm::partition_point(AllSpelledTokens, [&](const syntax::Token &Tok) {
+          return SM.getFileOffset(Tok.endLocation()) <= SelBegin;
+        });
+    const syntax::Token *SelLimit = std::partition_point(
+        SelFirst, AllSpelledTokens.end(), [&](const syntax::Token &Tok) {
+          return SM.getFileOffset(Tok.location()) < SelEnd;
+        });
+    // Precompute selectedness and offset for selected spelled tokens.
+    for (const syntax::Token *T = SelFirst; T < SelLimit; ++T) {
       // As well as comments, don't count semicolons as real tokens.
       // They're not properly claimed as expr-statement is missing from the 
AST.
-      if (Tok.kind() == tok::comment || Tok.kind() == tok::semi)
+      if (T->kind() == tok::comment || T->kind() == tok::semi)
         continue;
-
-      Tokens.emplace_back();
-      TokInfo &S = Tokens.back();
-      S.StartOffset = SM.getFileOffset(Tok.location());
-      S.EndOffset = S.StartOffset + Tok.length();
-      if (S.StartOffset >= SelBegin && S.EndOffset <= SelEnd)
+      SpelledTokens.emplace_back();
+      Tok &S = SpelledTokens.back();
+      S.Offset = SM.getFileOffset(T->location());
+      if (S.Offset >= SelBegin && S.Offset + T->length() <= SelEnd)
         S.Selected = SelectionTree::Complete;
-      else if (S.EndOffset > SelBegin && S.StartOffset < SelEnd)
-        S.Selected = SelectionTree::Partial;
       else
-        S.Selected = SelectionTree::Unselected;
-      S.Claimed = false;
+        S.Selected = SelectionTree::Partial;
     }
   }
 
-  // Associates any tokens overlapping [Begin, End) with an AST node.
-  // Tokens that were already claimed by another AST node are not claimed 
again.
-  // Updates Result if the node is selected in the sense of SelectionTree.
-  void claim(unsigned Begin, unsigned End, SelectionTree::Selection &Result) {
-    assert(Begin <= End);
+  // Test whether a consecutive range of tokens is selected.
+  // The tokens are taken from the expanded token stream.
+  SelectionTree::Selection
+  test(llvm::ArrayRef<syntax::Token> ExpandedTokens) const {
+    if (SpelledTokens.empty())
+      return NoTokens;
+    SelectionTree::Selection Result = NoTokens;
+    while (!ExpandedTokens.empty()) {
+      // Take consecutive tokens from the same context together for efficiency.
+      FileID FID = SM.getFileID(ExpandedTokens.front().location());
+      auto Batch = ExpandedTokens.take_while([&](const syntax::Token &T) {
+        return SM.getFileID(T.location()) == FID;
+      });
+      assert(!Batch.empty());
+      ExpandedTokens = ExpandedTokens.drop_front(Batch.size());
+
+      update(Result, testChunk(FID, Batch));
+    }
+    return Result;
+  }
 
-    // Fast-path for missing the selection entirely.
-    if (Begin >= SelEnd || End <= SelBegin)
-      return;
-
-    // We will consider the range (at least partially) selected if it hit any
-    // selected and previously unclaimed token.
-    bool ClaimedAnyToken = false;
-    // The selection is (at most) partial if:
-    // - any claimed token is partially selected
-    // - any token in the range is unselected
-    bool PartialSelection = false;
-
-    // Find the first token that (maybe) overlaps the claimed range.
-    auto Start = llvm::partition_point(Tokens, [&](const TokInfo &Tok) {
-      return Tok.EndOffset <= Begin;
-    });
-    // Iterate over every token that overlaps the range.
-    // Claim selected tokens, and update the two result flags.
-    for (auto It = Start; It != Tokens.end() && It->StartOffset < End; ++It) {
-      if (It->Selected) {
-        if (!It->Claimed) {
-          // Token is selected, in the node's range, and unclaimed; claim it.
-          It->Claimed = true;
-          ClaimedAnyToken = true;
-          // If the token was only partially selected, so is the node.
-          PartialSelection |= (It->Selected == SelectionTree::Partial);
-        }
-      } else {
-        // If the node covers an unselected token, it's not completely 
selected.
-        PartialSelection = true;
+  // Cheap check whether any of the tokens in R might be selected.
+  // If it returns false, test() will return NoTokens or Unselected.
+  // If it returns true, test() may return any value.
+  bool mayHit(SourceRange R) const {
+    if (SpelledTokens.empty())
+      return false;
+    auto B = SM.getDecomposedLoc(R.getBegin());
+    auto E = SM.getDecomposedLoc(R.getEnd());
+    if (B.first == SelFile && E.first == SelFile)
+      if (E.second < SpelledTokens.front().Offset ||
+          B.second > SpelledTokens.back().Offset)
+        return false;
+    return true;
+  }
+
+private:
+  // Hit-test a consecutive range of tokens from a single file ID.
+  SelectionTree::Selection
+  testChunk(FileID FID, llvm::ArrayRef<syntax::Token> Batch) const {
+    assert(!Batch.empty());
+    SourceLocation StartLoc = Batch.front().location();
+    // There are several possible categories of FileID depending on how the
+    // preprocessor was used to generate these tokens:
+    //   main file, #included file, macro args, macro bodies.
+    // We need to identify the main-file tokens that represent Batch, and
+    // determine whether we want to exclusively claim them. Regular tokens
+    // represent one AST construct, but a macro invocation can represent many.
+
+    // Handle tokens written directly in the main file.
+    if (FID == SelFile) {
+      return testTokenRange(SM.getFileOffset(Batch.front().location()),
+                            SM.getFileOffset(Batch.back().location()));
+    }
+
+    // Handle tokens in another file #included into the main file.
+    // Check if the #include is selected, but don't claim it exclusively.
+    if (StartLoc.isFileID()) {
+      for (SourceLocation Loc = Batch.front().location(); Loc.isValid();
+           Loc = SM.getIncludeLoc(SM.getFileID(Loc))) {
+        if (SM.getFileID(Loc) == SelFile)
+          // FIXME: use whole #include directive, not just the filename string.
+          return testToken(SM.getFileOffset(Loc));
       }
+      return NoTokens;
     }
 
-    // If some tokens were previously claimed (Result != Unselected), we may
-    // upgrade from Partial->Complete, even if no new tokens were claimed.
-    // Important for [[int a]].
-    if (ClaimedAnyToken || Result) {
-      Result = std::max(Result, PartialSelection ? SelectionTree::Partial
-                                                 : SelectionTree::Complete);
+    assert(StartLoc.isMacroID());
+    // Handle tokens that were passed as a macro argument.
+    SourceLocation ArgStart = SM.getTopMacroCallerLoc(StartLoc);
+    if (SM.getFileID(ArgStart) == SelFile) {
+      SourceLocation ArgEnd = SM.getTopMacroCallerLoc(Batch.back().location());
+      return testTokenRange(SM.getFileOffset(ArgStart),
+                            SM.getFileOffset(ArgEnd));
     }
+
+    // Handle tokens produced by non-argument macro expansion.
+    // Check if the macro name is selected, don't claim it exclusively.
+    auto Expansion = SM.getDecomposedExpansionLoc(StartLoc);
+    if (Expansion.first == SelFile)
+      // FIXME: also check ( and ) for function-like macros?
+      return testToken(Expansion.second);
+    else
+      return NoTokens;
   }
 
-private:
-  struct TokInfo {
-    unsigned StartOffset;
-    unsigned EndOffset;
+  // Is the closed token range [Begin, End] selected?
+  SelectionTree::Selection testTokenRange(unsigned Begin, unsigned End) const {
+    assert(Begin <= End);
+    // Outside the selection entirely?
+    if (End < SpelledTokens.front().Offset ||
+        Begin > SpelledTokens.back().Offset)
+      return SelectionTree::Unselected;
+
+    // Compute range of tokens.
+    auto B = llvm::partition_point(
+        SpelledTokens, [&](const Tok &T) { return T.Offset < Begin; });
+    auto E = std::partition_point(
+        B, SpelledTokens.end(), [&](const Tok &T) { return T.Offset <= End; });
+
+    // Aggregate selectedness of tokens in range.
+    bool ExtendsOutsideSelection = Begin < SpelledTokens.front().Offset ||
+                                   End > SpelledTokens.back().Offset;
+    SelectionTree::Selection Result =
+        ExtendsOutsideSelection ? SelectionTree::Unselected : NoTokens;
+    for (auto It = B; It != E; ++It)
+      update(Result, It->Selected);
+    return Result;
+  }
+
+  // Is the token at `Offset` selected?
+  SelectionTree::Selection testToken(unsigned Offset) const {
+    // Outside the selection entirely?
+    if (Offset < SpelledTokens.front().Offset ||
+        Offset > SpelledTokens.back().Offset)
+      return SelectionTree::Unselected;
+    // Find the token, if it exists.
+    auto It = llvm::partition_point(
+        SpelledTokens, [&](const Tok &T) { return T.Offset < Offset; });
+    if (It != SpelledTokens.end() && It->Offset == Offset)
+      return It->Selected;
+    return NoTokens;
+  }
+
+  struct Tok {
+    unsigned Offset;
     SelectionTree::Selection Selected;
-    bool Claimed;
-    bool operator<(const TokInfo &Other) const {
-      return StartOffset < Other.StartOffset;
-    }
   };
-  std::vector<TokInfo> Tokens;
-  unsigned SelBegin, SelEnd;
+  std::vector<Tok> SpelledTokens;
+  FileID SelFile;
+  const SourceManager &SM;
 };
 
 // Show the type of a node for debugging.
@@ -195,16 +383,6 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
     V.TraverseAST(AST);
     assert(V.Stack.size() == 1 && "Unpaired push/pop?");
     assert(V.Stack.top() == &V.Nodes.front());
-    // We selected TUDecl if tokens were unclaimed (or the file is empty).
-    SelectionTree::Selection UnclaimedTokens = SelectionTree::Unselected;
-    V.Claimed.claim(Begin, End, UnclaimedTokens);
-    if (UnclaimedTokens || V.Nodes.size() == 1) {
-      StringRef FileContent = AST.getSourceManager().getBufferData(File);
-      // Don't require the trailing newlines to be selected.
-      bool SelectedAll = Begin == 0 && End >= FileContent.rtrim().size();
-      V.Stack.top()->Selected =
-          SelectedAll ? SelectionTree::Complete : SelectionTree::Partial;
-    }
     return std::move(V.Nodes);
   }
 
@@ -289,11 +467,8 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
 #ifndef NDEBUG
         PrintPolicy(PP),
 #endif
-        Claimed(Tokens.spelledTokens(SelFile), SM, SelBegin, SelEnd),
-        SelFile(SelFile),
-        SelBeginTokenStart(SM.getFileOffset(Lexer::GetBeginningOfToken(
-            SM.getComposedLoc(SelFile, SelBegin), SM, LangOpts))),
-        SelEnd(SelEnd) {
+        TokenBuf(Tokens), SelChecker(Tokens, SelFile, SelBegin, SelEnd, SM),
+        UnclaimedExpandedTokens(Tokens.expandedTokens()) {
     // Ensure we have a node for the TU decl, regardless of traversal scope.
     Nodes.emplace_back();
     Nodes.back().ASTNode = DynTypedNode::create(*AST.getTranslationUnitDecl());
@@ -346,18 +521,12 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
   // don't intersect the selection may be recursively skipped.
   bool canSafelySkipNode(const DynTypedNode &N) {
     SourceRange S = N.getSourceRange();
-    auto B = SM.getDecomposedLoc(S.getBegin());
-    auto E = SM.getDecomposedLoc(S.getEnd());
-    // Node lies in a macro expansion?
-    if (B.first != SelFile || E.first != SelFile)
-      return false;
-    // Node intersects selection tokens?
-    if (B.second < SelEnd && E.second >= SelBeginTokenStart)
-      return false;
-    // Otherwise, allow skipping over the node.
-    dlog("{1}skip: {0}", printNodeToString(N, PrintPolicy), indent());
-    dlog("{1}skipped range = {0}", S.printToString(SM), indent(1));
-    return true;
+    if (!SelChecker.mayHit(S)) {
+      dlog("{1}skip: {0}", printNodeToString(N, PrintPolicy), indent());
+      dlog("{1}skipped range = {0}", S.printToString(SM), indent(1));
+      return true;
+    }
+    return false;
   }
 
   // There are certain nodes we want to treat as leaves in the SelectionTree,
@@ -377,11 +546,9 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
     Nodes.emplace_back();
     Nodes.back().ASTNode = std::move(Node);
     Nodes.back().Parent = Stack.top();
+    Nodes.back().Selected = NoTokens;
     Stack.push(&Nodes.back());
     claimRange(Early, Nodes.back().Selected);
-    // Early hit detection never selects the whole node.
-    if (Nodes.back().Selected)
-      Nodes.back().Selected = SelectionTree::Partial;
   }
 
   // Pops a node off the ancestor stack, and finalizes it. Pairs with push().
@@ -390,6 +557,8 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
     Node &N = *Stack.top();
     dlog("{1}pop: {0}", printNodeToString(N.ASTNode, PrintPolicy), indent(-1));
     claimRange(N.ASTNode.getSourceRange(), N.Selected);
+    if (N.Selected == NoTokens)
+      N.Selected = SelectionTree::Unselected;
     if (N.Selected || !N.Children.empty()) {
       // Attach to the tree.
       N.Parent->Children.push_back(&N);
@@ -424,31 +593,12 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
   // This is usually called from pop(), so we can take children into account.
   // The existing state of Result is relevant (early/late claims can interact).
   void claimRange(SourceRange S, SelectionTree::Selection &Result) {
-    if (!S.isValid())
-      return;
-    // toHalfOpenFileRange() allows selection of constructs in macro args. e.g:
-    //   #define LOOP_FOREVER(Body) for(;;) { Body }
-    //   void IncrementLots(int &x) {
-    //     LOOP_FOREVER( ++x; )
-    //   }
-    // Selecting "++x" or "x" will do the right thing.
-    auto Range = toHalfOpenFileRange(SM, LangOpts, S);
-    assert(Range && "We should be able to get the File Range");
-    dlog("{1}claimRange: {0}", Range->printToString(SM), indent());
-    auto B = SM.getDecomposedLoc(Range->getBegin());
-    auto E = SM.getDecomposedLoc(Range->getEnd());
-    // Otherwise, nodes in macro expansions can't be selected.
-    if (B.first != SelFile || E.first != SelFile)
-      return;
-    // Attempt to claim the remaining range. If there's nothing to claim, only
-    // children were selected.
-    Claimed.claim(B.second, E.second, Result);
-    if (Result)
-      dlog("{1}hit selection: {0}",
-           SourceRange(SM.getComposedLoc(B.first, B.second),
-                       SM.getComposedLoc(E.first, E.second))
-               .printToString(SM),
-           indent());
+    for (const auto &ClaimedRange :
+         UnclaimedExpandedTokens.erase(TokenBuf.expandedTokens(S)))
+      update(Result, SelChecker.test(ClaimedRange));
+
+    if (Result && Result != NoTokens)
+      dlog("{1}hit selection: {0}", S.printToString(SM), indent());
   }
 
   std::string indent(int Offset = 0) {
@@ -463,17 +613,11 @@ class SelectionVisitor : public 
RecursiveASTVisitor<SelectionVisitor> {
 #ifndef NDEBUG
   const PrintingPolicy &PrintPolicy;
 #endif
+  const syntax::TokenBuffer &TokenBuf;
   std::stack<Node *> Stack;
-  SelectedTokens Claimed;
+  SelectionTester SelChecker;
+  IntervalSet<syntax::Token> UnclaimedExpandedTokens;
   std::deque<Node> Nodes; // Stable pointers as we add more nodes.
-  FileID SelFile;
-  // If the selection start slices a token in half, the beginning of that 
token.
-  // This is useful for checking whether the end of a token range overlaps
-  // the selection: range.end < SelBeginTokenStart is equivalent to
-  // range.end + measureToken(range.end) < SelBegin (assuming range.end points
-  // to a token), and it saves a lex every time.
-  unsigned SelBeginTokenStart;
-  unsigned SelEnd;
 };
 
 } // namespace

diff  --git a/clang-tools-extra/clangd/Selection.h 
b/clang-tools-extra/clangd/Selection.h
index 9bcb9d5fb01f..a7050c49be6b 100644
--- a/clang-tools-extra/clangd/Selection.h
+++ b/clang-tools-extra/clangd/Selection.h
@@ -76,7 +76,7 @@ class SelectionTree {
                 unsigned Start, unsigned End);
 
   // Describes to what extent an AST node is covered by the selection.
-  enum Selection {
+  enum Selection : unsigned char {
     // The AST node owns no characters covered by the selection.
     // Note that characters owned by children don't count:
     //   if (x == 0) scream();

diff  --git a/clang-tools-extra/clangd/unittests/SelectionTests.cpp 
b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
index 6f4ccd88b978..ec9fd4185d94 100644
--- a/clang-tools-extra/clangd/unittests/SelectionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
@@ -134,6 +134,15 @@ TEST(SelectionTest, CommonAncestor) {
           )cpp",
           "IfStmt",
       },
+      {
+          R"cpp(
+            int x(int);
+            #define M(foo) x(foo)
+            int a = 42;
+            int b = M([[^a]]);
+          )cpp",
+          "DeclRefExpr",
+      },
       {
           R"cpp(
             void foo();
@@ -378,6 +387,7 @@ TEST(SelectionTest, Selected) {
             $C[[return]];
           }]] else [[{^
           }]]]]
+          char z;
         }
       )cpp",
       R"cpp(
@@ -386,10 +396,10 @@ TEST(SelectionTest, Selected) {
           void foo(^$C[[unique_ptr<$C[[unique_ptr<$C[[int]]>]]>]]^ a) {}
       )cpp",
       R"cpp(int a = [[5 >^> 1]];)cpp",
-      R"cpp([[
+      R"cpp(
         #define ECHO(X) X
-        ECHO(EC^HO([[$C[[int]]) EC^HO(a]]));
-      ]])cpp",
+        ECHO(EC^HO($C[[int]]) EC^HO(a));
+      )cpp",
       R"cpp( $C[[^$C[[int]] a^]]; )cpp",
       R"cpp( $C[[^$C[[int]] a = $C[[5]]^]]; )cpp",
   };
@@ -428,6 +438,56 @@ TEST(SelectionTest, PathologicalPreprocessor) {
   EXPECT_EQ("WhileStmt", T.commonAncestor()->Parent->kind());
 }
 
+TEST(SelectionTest, IncludedFile) {
+  const char *Case = R"cpp(
+    void test() {
+#include "Exp^and.inc"
+        break;
+    }
+  )cpp";
+  Annotations Test(Case);
+  auto TU = TestTU::withCode(Test.code());
+  TU.AdditionalFiles["Expand.inc"] = "while(1)\n";
+  auto AST = TU.build();
+  auto T = makeSelectionTree(Case, AST);
+
+  EXPECT_EQ("WhileStmt", T.commonAncestor()->kind());
+}
+
+TEST(SelectionTest, MacroArgExpansion) {
+  // If a macro arg is expanded several times, we consider them all selected.
+  const char *Case = R"cpp(
+    int mul(int, int);
+    #define SQUARE(X) mul(X, X);
+    int nine = SQUARE(^3);
+  )cpp";
+  Annotations Test(Case);
+  auto AST = TestTU::withCode(Test.code()).build();
+  auto T = makeSelectionTree(Case, AST);
+  // Unfortunately, this makes the common ancestor the CallExpr...
+  // FIXME: hack around this by picking one?
+  EXPECT_EQ("CallExpr", T.commonAncestor()->kind());
+  EXPECT_FALSE(T.commonAncestor()->Selected);
+  EXPECT_EQ(2u, T.commonAncestor()->Children.size());
+  for (const auto* N : T.commonAncestor()->Children) {
+    EXPECT_EQ("IntegerLiteral", N->kind());
+    EXPECT_TRUE(N->Selected);
+  }
+
+  // Verify that the common assert() macro doesn't suffer from this.
+  // (This is because we don't associate the stringified token with the arg).
+  Case = R"cpp(
+    void die(const char*);
+    #define assert(x) (x ? (void)0 : die(#x)
+    void foo() { assert(^42); }
+  )cpp";
+  Test = Annotations(Case);
+  AST = TestTU::withCode(Test.code()).build();
+  T = makeSelectionTree(Case, AST);
+
+  EXPECT_EQ("IntegerLiteral", T.commonAncestor()->kind());
+}
+
 TEST(SelectionTest, Implicit) {
   const char* Test = R"cpp(
     struct S { S(const char*); };

diff  --git a/clang-tools-extra/clangd/unittests/TweakTests.cpp 
b/clang-tools-extra/clangd/unittests/TweakTests.cpp
index 4e481241acd8..dc7699904019 100644
--- a/clang-tools-extra/clangd/unittests/TweakTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TweakTests.cpp
@@ -269,7 +269,7 @@ TEST_F(ExtractVariableTest, Test) {
   EXPECT_UNAVAILABLE(UnavailableCases);
 
   // vector of pairs of input and output strings
-  const std::vector<std::pair<llvm::StringLiteral, llvm::StringLiteral>>
+  const std::vector<std::pair<std::string, std::string>>
       InputOutputs = {
           // extraction from variable declaration/assignment
           {R"cpp(void varDecl() {
@@ -321,17 +321,10 @@ TEST_F(ExtractVariableTest, Test) {
                    if(1)
                     LOOP(5 + [[3]])
                  })cpp",
-           /*FIXME: It should be extracted like this. SelectionTree needs to be
-             * fixed for macros.
             R"cpp(#define LOOP(x) while (1) {a = x;}
-                void f(int a) {
-                  auto dummy = 3; if(1)
-                   LOOP(5 + dummy)
-                })cpp"},*/
-           R"cpp(#define LOOP(x) while (1) {a = x;}
                  void f(int a) {
-                   auto dummy = LOOP(5 + 3); if(1)
-                    dummy
+                   auto dummy = 3; if(1)
+                    LOOP(5 + dummy)
                  })cpp"},
           {R"cpp(#define LOOP(x) do {x;} while(1);
                  void f(int a) {
@@ -644,13 +637,18 @@ void f(const int c) {
   )cpp";
   EXPECT_EQ(apply(TemplateFailInput), "unavailable");
 
-  // FIXME: This should be extractable after selectionTree works correctly for
-  // macros (currently it doesn't select anything for the following case)
-  std::string MacroFailInput = R"cpp(
+  std::string MacroInput = R"cpp(
     #define F(BODY) void f() { BODY }
     F ([[int x = 0;]])
   )cpp";
-  EXPECT_EQ(apply(MacroFailInput), "unavailable");
+  std::string MacroOutput = R"cpp(
+    #define F(BODY) void f() { BODY }
+    void extracted() {
+int x = 0;
+}
+F (extracted();)
+  )cpp";
+  EXPECT_EQ(apply(MacroInput), MacroOutput);
 
   // Shouldn't crash.
   EXPECT_EQ(apply("void f([[int a]]);"), "unavailable");

diff  --git a/clang/include/clang/Tooling/Syntax/Tokens.h 
b/clang/include/clang/Tooling/Syntax/Tokens.h
index 301432d3888b..6f4d0e0c050a 100644
--- a/clang/include/clang/Tooling/Syntax/Tokens.h
+++ b/clang/include/clang/Tooling/Syntax/Tokens.h
@@ -175,6 +175,7 @@ class TokenBuffer {
   /// All tokens produced by the preprocessor after all macro replacements,
   /// directives, etc. Source locations found in the clang AST will always
   /// point to one of these tokens.
+  /// Tokens are in TU order (per SourceManager::isBeforeInTranslationUnit()).
   /// FIXME: figure out how to handle token splitting, e.g. '>>' can be split
   ///        into two '>' tokens by the parser. However, TokenBuffer currently
   ///        keeps it as a single '>>' token.
@@ -182,6 +183,10 @@ class TokenBuffer {
     return ExpandedTokens;
   }
 
+  /// Returns the subrange of expandedTokens() corresponding to the closed
+  /// token range R.
+  llvm::ArrayRef<syntax::Token> expandedTokens(SourceRange R) const;
+
   /// Find the subrange of spelled tokens that produced the corresponding \p
   /// Expanded tokens.
   ///

diff  --git a/clang/lib/Tooling/Syntax/Tokens.cpp 
b/clang/lib/Tooling/Syntax/Tokens.cpp
index a2c3bc137d6b..5941507e086d 100644
--- a/clang/lib/Tooling/Syntax/Tokens.cpp
+++ b/clang/lib/Tooling/Syntax/Tokens.cpp
@@ -119,6 +119,22 @@ llvm::StringRef FileRange::text(const SourceManager &SM) 
const {
   return Text.substr(Begin, length());
 }
 
+llvm::ArrayRef<syntax::Token> TokenBuffer::expandedTokens(SourceRange R) const 
{
+  if (R.isInvalid())
+    return {};
+  const Token *Begin =
+      llvm::partition_point(expandedTokens(), [&](const syntax::Token &T) {
+        return SourceMgr->isBeforeInTranslationUnit(T.location(), 
R.getBegin());
+      });
+  const Token *End =
+      llvm::partition_point(expandedTokens(), [&](const syntax::Token &T) {
+        return !SourceMgr->isBeforeInTranslationUnit(R.getEnd(), T.location());
+      });
+  if (Begin > End)
+    return {};
+  return {Begin, End};
+}
+
 std::pair<const syntax::Token *, const TokenBuffer::Mapping *>
 TokenBuffer::spelledForExpandedToken(const syntax::Token *Expanded) const {
   assert(Expanded);

diff  --git a/clang/unittests/Tooling/Syntax/TokensTest.cpp 
b/clang/unittests/Tooling/Syntax/TokensTest.cpp
index 6ffe2c43dd0f..2c462d49ee41 100644
--- a/clang/unittests/Tooling/Syntax/TokensTest.cpp
+++ b/clang/unittests/Tooling/Syntax/TokensTest.cpp
@@ -40,6 +40,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Testing/Support/Annotations.h"
 #include "llvm/Testing/Support/SupportHelpers.h"
+#include "gmock/gmock.h"
 #include <cassert>
 #include <cstdlib>
 #include <gmock/gmock.h>
@@ -663,6 +664,20 @@ TEST_F(TokenBufferTest, SpelledByExpanded) {
               ValueIs(SameRange(findSpelled("not_mapped"))));
 }
 
+TEST_F(TokenBufferTest, ExpandedTokensForRange) {
+  recordTokens(R"cpp(
+    #define SIGN(X) X##_washere
+    A SIGN(B) C SIGN(D) E SIGN(F) G
+  )cpp");
+
+  SourceRange R(findExpanded("C").front().location(),
+                findExpanded("F_washere").front().location());
+  // Sanity check: expanded and spelled tokens are stored separately.
+  EXPECT_THAT(Buffer.expandedTokens(R),
+              SameRange(findExpanded("C D_washere E F_washere")));
+  EXPECT_THAT(Buffer.expandedTokens(SourceRange()), testing::IsEmpty());
+}
+
 TEST_F(TokenBufferTest, ExpansionStartingAt) {
   // Object-like macro expansions.
   recordTokens(R"cpp(


        
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