1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
| //===--- Selection.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "Selection.h"
#include "Logger.h"
#include "SourceCode.h"
#include "clang/AST/ASTTypeTraits.h"
#include "clang/AST/PrettyPrinter.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TokenKinds.h"
#include "clang/Lex/Lexer.h"
#include "clang/Tooling/Syntax/Tokens.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <string>
namespace clang {
namespace clangd {
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 {
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) {
// 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)
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)
S.Selected = SelectionTree::Complete;
else if (S.EndOffset > SelBegin && S.StartOffset < SelEnd)
S.Selected = SelectionTree::Partial;
else
S.Selected = SelectionTree::Unselected;
S.Claimed = false;
}
}
// 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);
// 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;
}
}
// 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);
}
}
private:
struct TokInfo {
unsigned StartOffset;
unsigned EndOffset;
SelectionTree::Selection Selected;
bool Claimed;
bool operator<(const TokInfo &Other) const {
return StartOffset < Other.StartOffset;
}
};
std::vector<TokInfo> Tokens;
unsigned SelBegin, SelEnd;
};
// Show the type of a node for debugging.
void printNodeKind(llvm::raw_ostream &OS, const DynTypedNode &N) {
if (const TypeLoc *TL = N.get<TypeLoc>()) {
// TypeLoc is a hierarchy, but has only a single ASTNodeKind.
// Synthesize the name from the Type subclass (except for QualifiedTypeLoc).
if (TL->getTypeLocClass() == TypeLoc::Qualified)
OS << "QualifiedTypeLoc";
else
OS << TL->getType()->getTypeClassName() << "TypeLoc";
} else {
OS << N.getNodeKind().asStringRef();
}
}
#ifndef NDEBUG
std::string printNodeToString(const DynTypedNode &N, const PrintingPolicy &PP) {
std::string S;
llvm::raw_string_ostream OS(S);
printNodeKind(OS, N);
OS << " ";
return std::move(OS.str());
}
#endif
// We find the selection by visiting written nodes in the AST, looking for nodes
// that intersect with the selected character range.
//
// While traversing, we maintain a parent stack. As nodes pop off the stack,
// we decide whether to keep them or not. To be kept, they must either be
// selected or contain some nodes that are.
//
// For simple cases (not inside macros) we prune subtrees that don't intersect.
class SelectionVisitor : public RecursiveASTVisitor<SelectionVisitor> {
public:
// Runs the visitor to gather selected nodes and their ancestors.
// If there is any selection, the root (TUDecl) is the first node.
static std::deque<Node> collect(ASTContext &AST,
const syntax::TokenBuffer &Tokens,
const PrintingPolicy &PP, unsigned Begin,
unsigned End, FileID File) {
SelectionVisitor V(AST, Tokens, PP, Begin, End, File);
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);
}
// We traverse all "well-behaved" nodes the same way:
// - push the node onto the stack
// - traverse its children recursively
// - pop it from the stack
// - hit testing: is intersection(node, selection) - union(children) empty?
// - attach it to the tree if it or any children hit the selection
//
// Two categories of nodes are not "well-behaved":
// - those without source range information, we don't record those
// - those that can't be stored in DynTypedNode.
// We're missing some interesting things like Attr due to the latter.
bool TraverseDecl(Decl *X) {
if (X && isa<TranslationUnitDecl>(X))
return Base::TraverseDecl(X); // Already pushed by constructor.
// Base::TraverseDecl will suppress children, but not this node itself.
if (X && X->isImplicit())
return true;
return traverseNode(X, [&] { return Base::TraverseDecl(X); });
}
bool TraverseTypeLoc(TypeLoc X) {
return traverseNode(&X, [&] { return Base::TraverseTypeLoc(X); });
}
bool TraverseNestedNameSpecifierLoc(NestedNameSpecifierLoc X) {
return traverseNode(
&X, [&] { return Base::TraverseNestedNameSpecifierLoc(X); });
}
bool TraverseConstructorInitializer(CXXCtorInitializer *X) {
return traverseNode(
X, [&] { return Base::TraverseConstructorInitializer(X); });
}
// Stmt is the same, but this form allows the data recursion optimization.
bool dataTraverseStmtPre(Stmt *X) {
if (!X)
return false;
// Implicit this in a MemberExpr is not filtered out by RecursiveASTVisitor.
// It would be nice if RAV handled this (!shouldTRaverseImplicitCode()).
if (auto *CTI = llvm::dyn_cast<CXXThisExpr>(X))
if (CTI->isImplicit())
return false;
auto N = DynTypedNode::create(*X);
if (canSafelySkipNode(N))
return false;
push(std::move(N));
return true;
}
bool dataTraverseStmtPost(Stmt *X) {
pop();
return true;
}
// QualifiedTypeLoc is handled strangely in RecursiveASTVisitor: the derived
// TraverseTypeLoc is not called for the inner UnqualTypeLoc.
// This means we'd never see 'int' in 'const int'! Work around that here.
// (The reason for the behavior is to avoid traversing the nested Type twice,
// but we ignore TraverseType anyway).
bool TraverseQualifiedTypeLoc(QualifiedTypeLoc QX) {
return traverseNode<TypeLoc>(
&QX, [&] { return TraverseTypeLoc(QX.getUnqualifiedLoc()); });
}
// Uninteresting parts of the AST that don't have locations within them.
bool TraverseNestedNameSpecifier(NestedNameSpecifier *) { return true; }
bool TraverseType(QualType) { return true; }
// The DeclStmt for the loop variable claims to cover the whole range
// inside the parens, this causes the range-init expression to not be hit.
// Traverse the loop VarDecl instead, which has the right source range.
bool TraverseCXXForRangeStmt(CXXForRangeStmt *S) {
return traverseNode(S, [&] {
return TraverseStmt(S->getInit()) && TraverseDecl(S->getLoopVariable()) &&
TraverseStmt(S->getRangeInit()) && TraverseStmt(S->getBody());
});
}
private:
using Base = RecursiveASTVisitor<SelectionVisitor>;
SelectionVisitor(ASTContext &AST, const syntax::TokenBuffer &Tokens,
const PrintingPolicy &PP, unsigned SelBegin, unsigned SelEnd,
FileID SelFile)
: SM(AST.getSourceManager()), LangOpts(AST.getLangOpts()),
#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) {
// Ensure we have a node for the TU decl, regardless of traversal scope.
Nodes.emplace_back();
Nodes.back().ASTNode = DynTypedNode::create(*AST.getTranslationUnitDecl());
Nodes.back().Parent = nullptr;
Nodes.back().Selected = SelectionTree::Unselected;
Stack.push(&Nodes.back());
}
// Generic case of TraverseFoo. Func should be the call to Base::TraverseFoo.
// Node is always a pointer so the generic code can handle any null checks.
template <typename T, typename Func>
bool traverseNode(T *Node, const Func &Body) {
if (Node == nullptr)
return true;
auto N = DynTypedNode::create(*Node);
if (canSafelySkipNode(N))
return true;
push(DynTypedNode::create(*Node));
bool Ret = Body();
pop();
return Ret;
}
// HIT TESTING
//
// We do rough hit testing on the way down the tree to avoid traversing
// subtrees that don't touch the selection (canSafelySkipNode), but
// fine-grained hit-testing is mostly done on the way back up (in pop()).
// This means children get to claim parts of the selection first, and parents
// are only selected if they own tokens that no child owned.
//
// Nodes *usually* nest nicely: a child's getSourceRange() lies within the
// parent's, and a node (transitively) owns all tokens in its range.
//
// Exception 1: child range claims tokens that should be owned by the parent.
// e.g. in `void foo(int);`, the FunctionTypeLoc should own
// `void (int)` but the parent FunctionDecl should own `foo`.
// To handle this case, certain nodes claim small token ranges *before*
// their children are traversed. (see earlySourceRange).
//
// Exception 2: siblings both claim the same node.
// e.g. `int x, y;` produces two sibling VarDecls.
// ~~~~~ x
// ~~~~~~~~ y
// Here the first ("leftmost") sibling claims the tokens it wants, and the
// other sibling gets what's left. So selecting "int" only includes the left
// VarDecl in the selection tree.
// An optimization for a common case: nodes outside macro expansions that
// 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;
}
// Pushes a node onto the ancestor stack. Pairs with pop().
// Performs early hit detection for some nodes (on the earlySourceRange).
void push(DynTypedNode Node) {
SourceRange Early = earlySourceRange(Node);
dlog("{1}push: {0}", printNodeToString(Node, PrintPolicy), indent());
Nodes.emplace_back();
Nodes.back().ASTNode = std::move(Node);
Nodes.back().Parent = Stack.top();
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().
// Performs primary hit detection.
void pop() {
Node &N = *Stack.top();
dlog("{1}pop: {0}", printNodeToString(N.ASTNode, PrintPolicy), indent(-1));
claimRange(N.ASTNode.getSourceRange(), N.Selected);
if (N.Selected || !N.Children.empty()) {
// Attach to the tree.
N.Parent->Children.push_back(&N);
} else {
// Neither N any children are selected, it doesn't belong in the tree.
assert(&N == &Nodes.back());
Nodes.pop_back();
}
Stack.pop();
}
// Returns the range of tokens that this node will claim directly, and
// is not available to the node's children.
// Usually empty, but sometimes children cover tokens but shouldn't own them.
SourceRange earlySourceRange(const DynTypedNode &N) {
if (const Decl *D = N.get<Decl>()) {
// void [[foo]]();
if (auto *FD = llvm::dyn_cast<FunctionDecl>(D))
return FD->getNameInfo().getSourceRange();
// int (*[[s]])();
else if (auto *VD = llvm::dyn_cast<VarDecl>(D))
return VD->getLocation();
}
return SourceRange();
}
// Perform hit-testing of a complete Node against the selection.
// This runs for every node in the AST, and must be fast in common cases.
// 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());
}
std::string indent(int Offset = 0) {
// Cast for signed arithmetic.
int Amount = int(Stack.size()) + Offset;
assert(Amount >= 0);
return std::string(Amount, ' ');
}
SourceManager &SM;
const LangOptions &LangOpts;
#ifndef NDEBUG
const PrintingPolicy &PrintPolicy;
#endif
std::stack<Node *> Stack;
SelectedTokens Claimed;
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
void SelectionTree::print(llvm::raw_ostream &OS, const SelectionTree::Node &N,
int Indent) const {
if (N.Selected)
OS.indent(Indent - 1) << (N.Selected == SelectionTree::Complete ? '*'
: '.');
else
OS.indent(Indent);
printNodeKind(OS, N.ASTNode);
OS << ' ';
N.ASTNode.print(OS, PrintPolicy);
OS << "\n";
for (const Node *Child : N.Children)
print(OS, *Child, Indent + 2);
}
std::string SelectionTree::Node::kind() const {
std::string S;
llvm::raw_string_ostream OS(S);
printNodeKind(OS, ASTNode);
return std::move(OS.str());
}
// Decide which selection emulates a "point" query in between characters.
static std::pair<unsigned, unsigned> pointBounds(unsigned Offset, FileID FID,
ASTContext &AST) {
StringRef Buf = AST.getSourceManager().getBufferData(FID);
// Edge-cases where the choice is forced.
if (Buf.size() == 0)
return {0, 0};
if (Offset == 0)
return {0, 1};
if (Offset == Buf.size())
return {Offset - 1, Offset};
// We could choose either this byte or the previous. Usually we prefer the
// character on the right of the cursor (or under a block cursor).
// But if that's whitespace, we likely want the token on the left.
if (isWhitespace(Buf[Offset]) && !isWhitespace(Buf[Offset - 1]))
return {Offset - 1, Offset};
return {Offset, Offset + 1};
}
SelectionTree::SelectionTree(ASTContext &AST, const syntax::TokenBuffer &Tokens,
unsigned Begin, unsigned End)
: PrintPolicy(AST.getLangOpts()) {
// No fundamental reason the selection needs to be in the main file,
// but that's all clangd has needed so far.
const SourceManager &SM = AST.getSourceManager();
FileID FID = SM.getMainFileID();
if (Begin == End)
std::tie(Begin, End) = pointBounds(Begin, FID, AST);
PrintPolicy.TerseOutput = true;
PrintPolicy.IncludeNewlines = false;
dlog("Computing selection for {0}",
SourceRange(SM.getComposedLoc(FID, Begin), SM.getComposedLoc(FID, End))
.printToString(SM));
Nodes = SelectionVisitor::collect(AST, Tokens, PrintPolicy, Begin, End, FID);
Root = Nodes.empty() ? nullptr : &Nodes.front();
dlog("Built selection tree\n{0}", *this);
}
SelectionTree::SelectionTree(ASTContext &AST, const syntax::TokenBuffer &Tokens,
unsigned Offset)
: SelectionTree(AST, Tokens, Offset, Offset) {}
const Node *SelectionTree::commonAncestor() const {
const Node *Ancestor = Root;
while (Ancestor->Children.size() == 1 && !Ancestor->Selected)
Ancestor = Ancestor->Children.front();
// Returning nullptr here is a bit unprincipled, but it makes the API safer:
// the TranslationUnitDecl contains all of the preamble, so traversing it is a
// performance cliff. Callers can check for null and use root() if they want.
return Ancestor != Root ? Ancestor : nullptr;
}
const DeclContext& SelectionTree::Node::getDeclContext() const {
for (const Node* CurrentNode = this; CurrentNode != nullptr;
CurrentNode = CurrentNode->Parent) {
if (const Decl* Current = CurrentNode->ASTNode.get<Decl>()) {
if (CurrentNode != this)
if (auto *DC = dyn_cast<DeclContext>(Current))
return *DC;
return *Current->getDeclContext();
}
}
llvm_unreachable("A tree must always be rooted at TranslationUnitDecl.");
}
const SelectionTree::Node &SelectionTree::Node::ignoreImplicit() const {
if (Children.size() == 1 &&
Children.front()->ASTNode.getSourceRange() == ASTNode.getSourceRange())
return Children.front()->ignoreImplicit();
return *this;
}
const SelectionTree::Node &SelectionTree::Node::outerImplicit() const {
if (Parent && Parent->ASTNode.getSourceRange() == ASTNode.getSourceRange())
return Parent->outerImplicit();
return *this;
}
} // namespace clangd
} // namespace clang
|