1//===--- Quality.cpp ---------------------------------------------*- C++-*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "Quality.h"
10#include "AST.h"
11#include "ASTSignals.h"
12#include "FileDistance.h"
13#include "SourceCode.h"
14#include "index/Symbol.h"
15#include "clang/AST/ASTContext.h"
16#include "clang/AST/Decl.h"
17#include "clang/AST/DeclCXX.h"
18#include "clang/AST/DeclTemplate.h"
19#include "clang/AST/DeclVisitor.h"
20#include "clang/Basic/SourceManager.h"
21#include "clang/Sema/CodeCompleteConsumer.h"
22#include "llvm/ADT/StringRef.h"
23#include "llvm/Support/Casting.h"
24#include "llvm/Support/FormatVariadic.h"
25#include "llvm/Support/MathExtras.h"
26#include "llvm/Support/raw_ostream.h"
27#include <algorithm>
28#include <cmath>
29#include <optional>
30
31namespace clang {
32namespace clangd {
33
34static bool hasDeclInMainFile(const Decl &D) {
35 auto &SourceMgr = D.getASTContext().getSourceManager();
36 for (auto *Redecl : D.redecls()) {
37 if (isInsideMainFile(Redecl->getLocation(), SourceMgr))
38 return true;
39 }
40 return false;
41}
42
43static bool hasUsingDeclInMainFile(const CodeCompletionResult &R) {
44 const auto &Context = R.Declaration->getASTContext();
45 const auto &SourceMgr = Context.getSourceManager();
46 if (R.ShadowDecl) {
47 if (isInsideMainFile(R.ShadowDecl->getLocation(), SourceMgr))
48 return true;
49 }
50 return false;
51}
52
53static SymbolQualitySignals::SymbolCategory categorize(const NamedDecl &ND) {
54 if (const auto *FD = dyn_cast<FunctionDecl>(&ND)) {
55 if (FD->isOverloadedOperator())
56 return SymbolQualitySignals::Operator;
57 }
58 class Switch
59 : public ConstDeclVisitor<Switch, SymbolQualitySignals::SymbolCategory> {
60 public:
61#define MAP(DeclType, Category) \
62 SymbolQualitySignals::SymbolCategory Visit##DeclType(const DeclType *) { \
63 return SymbolQualitySignals::Category; \
64 }
65 MAP(NamespaceDecl, Namespace);
66 MAP(NamespaceAliasDecl, Namespace);
67 MAP(TypeDecl, Type);
68 MAP(TypeAliasTemplateDecl, Type);
69 MAP(ClassTemplateDecl, Type);
70 MAP(CXXConstructorDecl, Constructor);
71 MAP(CXXDestructorDecl, Destructor);
72 MAP(ValueDecl, Variable);
73 MAP(VarTemplateDecl, Variable);
74 MAP(FunctionDecl, Function);
75 MAP(FunctionTemplateDecl, Function);
76 MAP(Decl, Unknown);
77#undef MAP
78 };
79 return Switch().Visit(&ND);
80}
81
82static SymbolQualitySignals::SymbolCategory
83categorize(const CodeCompletionResult &R) {
84 if (R.Declaration)
85 return categorize(*R.Declaration);
86 if (R.Kind == CodeCompletionResult::RK_Macro)
87 return SymbolQualitySignals::Macro;
88 // Everything else is a keyword or a pattern. Patterns are mostly keywords
89 // too, except a few which we recognize by cursor kind.
90 switch (R.CursorKind) {
91 case CXCursor_CXXMethod:
92 return SymbolQualitySignals::Function;
93 case CXCursor_ModuleImportDecl:
94 return SymbolQualitySignals::Namespace;
95 case CXCursor_MacroDefinition:
96 return SymbolQualitySignals::Macro;
97 case CXCursor_TypeRef:
98 return SymbolQualitySignals::Type;
99 case CXCursor_MemberRef:
100 return SymbolQualitySignals::Variable;
101 case CXCursor_Constructor:
102 return SymbolQualitySignals::Constructor;
103 default:
104 return SymbolQualitySignals::Keyword;
105 }
106}
107
108static SymbolQualitySignals::SymbolCategory
109categorize(const index::SymbolInfo &D) {
110 switch (D.Kind) {
111 case index::SymbolKind::Namespace:
112 case index::SymbolKind::NamespaceAlias:
113 return SymbolQualitySignals::Namespace;
114 case index::SymbolKind::Macro:
115 return SymbolQualitySignals::Macro;
116 case index::SymbolKind::Enum:
117 case index::SymbolKind::Struct:
118 case index::SymbolKind::Class:
119 case index::SymbolKind::Protocol:
120 case index::SymbolKind::Extension:
121 case index::SymbolKind::Union:
122 case index::SymbolKind::TypeAlias:
123 case index::SymbolKind::TemplateTypeParm:
124 case index::SymbolKind::TemplateTemplateParm:
125 case index::SymbolKind::Concept:
126 return SymbolQualitySignals::Type;
127 case index::SymbolKind::Function:
128 case index::SymbolKind::ClassMethod:
129 case index::SymbolKind::InstanceMethod:
130 case index::SymbolKind::StaticMethod:
131 case index::SymbolKind::InstanceProperty:
132 case index::SymbolKind::ClassProperty:
133 case index::SymbolKind::StaticProperty:
134 case index::SymbolKind::ConversionFunction:
135 return SymbolQualitySignals::Function;
136 case index::SymbolKind::Destructor:
137 return SymbolQualitySignals::Destructor;
138 case index::SymbolKind::Constructor:
139 return SymbolQualitySignals::Constructor;
140 case index::SymbolKind::Variable:
141 case index::SymbolKind::Field:
142 case index::SymbolKind::EnumConstant:
143 case index::SymbolKind::Parameter:
144 case index::SymbolKind::NonTypeTemplateParm:
145 return SymbolQualitySignals::Variable;
146 case index::SymbolKind::Using:
147 case index::SymbolKind::Module:
148 case index::SymbolKind::Unknown:
149 return SymbolQualitySignals::Unknown;
150 }
151 llvm_unreachable("Unknown index::SymbolKind");
152}
153
154static bool isInstanceMember(const NamedDecl *ND) {
155 if (!ND)
156 return false;
157 if (const auto *TP = dyn_cast<FunctionTemplateDecl>(ND))
158 ND = TP->TemplateDecl::getTemplatedDecl();
159 if (const auto *CM = dyn_cast<CXXMethodDecl>(ND))
160 return !CM->isStatic();
161 return isa<FieldDecl>(ND); // Note that static fields are VarDecl.
162}
163
164static bool isInstanceMember(const index::SymbolInfo &D) {
165 switch (D.Kind) {
166 case index::SymbolKind::InstanceMethod:
167 case index::SymbolKind::InstanceProperty:
168 case index::SymbolKind::Field:
169 return true;
170 default:
171 return false;
172 }
173}
174
175void SymbolQualitySignals::merge(const CodeCompletionResult &SemaCCResult) {
176 Deprecated |= (SemaCCResult.Availability == CXAvailability_Deprecated);
177 Category = categorize(SemaCCResult);
178
179 if (SemaCCResult.Declaration) {
180 ImplementationDetail |= isImplementationDetail(SemaCCResult.Declaration);
181 if (auto *ID = SemaCCResult.Declaration->getIdentifier())
182 ReservedName = ReservedName || isReservedName(ID->getName());
183 } else if (SemaCCResult.Kind == CodeCompletionResult::RK_Macro)
184 ReservedName =
185 ReservedName || isReservedName(SemaCCResult.Macro->getName());
186}
187
188void SymbolQualitySignals::merge(const Symbol &IndexResult) {
189 Deprecated |= (IndexResult.Flags & Symbol::Deprecated);
190 ImplementationDetail |= (IndexResult.Flags & Symbol::ImplementationDetail);
191 References = std::max(IndexResult.References, References);
192 Category = categorize(IndexResult.SymInfo);
193 ReservedName = ReservedName || isReservedName(IndexResult.Name);
194}
195
196float SymbolQualitySignals::evaluateHeuristics() const {
197 float Score = 1;
198
199 // This avoids a sharp gradient for tail symbols, and also neatly avoids the
200 // question of whether 0 references means a bad symbol or missing data.
201 if (References >= 10) {
202 // Use a sigmoid style boosting function, which flats out nicely for large
203 // numbers (e.g. 2.58 for 1M references).
204 // The following boosting function is equivalent to:
205 // m = 0.06
206 // f = 12.0
207 // boost = f * sigmoid(m * std::log(References)) - 0.5 * f + 0.59
208 // Sample data points: (10, 1.00), (100, 1.41), (1000, 1.82),
209 // (10K, 2.21), (100K, 2.58), (1M, 2.94)
210 float S = std::pow(References, -0.06);
211 Score *= 6.0 * (1 - S) / (1 + S) + 0.59;
212 }
213
214 if (Deprecated)
215 Score *= 0.1f;
216 if (ReservedName)
217 Score *= 0.1f;
218 if (ImplementationDetail)
219 Score *= 0.2f;
220
221 switch (Category) {
222 case Keyword: // Often relevant, but misses most signals.
223 Score *= 4; // FIXME: important keywords should have specific boosts.
224 break;
225 case Type:
226 case Function:
227 case Variable:
228 Score *= 1.1f;
229 break;
230 case Namespace:
231 Score *= 0.8f;
232 break;
233 case Macro:
234 case Destructor:
235 case Operator:
236 Score *= 0.5f;
237 break;
238 case Constructor: // No boost constructors so they are after class types.
239 case Unknown:
240 break;
241 }
242
243 return Score;
244}
245
246llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
247 const SymbolQualitySignals &S) {
248 OS << llvm::formatv("=== Symbol quality: {0}\n", S.evaluateHeuristics());
249 OS << llvm::formatv("\tReferences: {0}\n", S.References);
250 OS << llvm::formatv("\tDeprecated: {0}\n", S.Deprecated);
251 OS << llvm::formatv("\tReserved name: {0}\n", S.ReservedName);
252 OS << llvm::formatv("\tImplementation detail: {0}\n", S.ImplementationDetail);
253 OS << llvm::formatv("\tCategory: {0}\n", static_cast<int>(S.Category));
254 return OS;
255}
256
257static SymbolRelevanceSignals::AccessibleScope
258computeScope(const NamedDecl *D) {
259 // Injected "Foo" within the class "Foo" has file scope, not class scope.
260 const DeclContext *DC = D->getDeclContext();
261 if (auto *R = dyn_cast_or_null<RecordDecl>(D))
262 if (R->isInjectedClassName())
263 DC = DC->getParent();
264 // Class constructor should have the same scope as the class.
265 if (isa<CXXConstructorDecl>(D))
266 DC = DC->getParent();
267 bool InClass = false;
268 for (; !DC->isFileContext(); DC = DC->getParent()) {
269 if (DC->isFunctionOrMethod())
270 return SymbolRelevanceSignals::FunctionScope;
271 InClass = InClass || DC->isRecord();
272 }
273 if (InClass)
274 return SymbolRelevanceSignals::ClassScope;
275 // ExternalLinkage threshold could be tweaked, e.g. module-visible as global.
276 // Avoid caching linkage if it may change after enclosing code completion.
277 if (hasUnstableLinkage(D) || D->getLinkageInternal() < ExternalLinkage)
278 return SymbolRelevanceSignals::FileScope;
279 return SymbolRelevanceSignals::GlobalScope;
280}
281
282void SymbolRelevanceSignals::merge(const Symbol &IndexResult) {
283 SymbolURI = IndexResult.CanonicalDeclaration.FileURI;
284 SymbolScope = IndexResult.Scope;
285 IsInstanceMember |= isInstanceMember(IndexResult.SymInfo);
286 if (!(IndexResult.Flags & Symbol::VisibleOutsideFile)) {
287 Scope = AccessibleScope::FileScope;
288 }
289 if (MainFileSignals) {
290 MainFileRefs =
291 std::max(MainFileRefs,
292 MainFileSignals->ReferencedSymbols.lookup(IndexResult.ID));
293 ScopeRefsInFile =
294 std::max(ScopeRefsInFile,
295 MainFileSignals->RelatedNamespaces.lookup(IndexResult.Scope));
296 }
297}
298
299void SymbolRelevanceSignals::computeASTSignals(
300 const CodeCompletionResult &SemaResult) {
301 if (!MainFileSignals)
302 return;
303 if ((SemaResult.Kind != CodeCompletionResult::RK_Declaration) &&
304 (SemaResult.Kind != CodeCompletionResult::RK_Pattern))
305 return;
306 if (const NamedDecl *ND = SemaResult.getDeclaration()) {
307 if (hasUnstableLinkage(ND))
308 return;
309 auto ID = getSymbolID(ND);
310 if (!ID)
311 return;
312 MainFileRefs =
313 std::max(MainFileRefs, MainFileSignals->ReferencedSymbols.lookup(ID));
314 if (const auto *NSD = dyn_cast<NamespaceDecl>(ND->getDeclContext())) {
315 if (NSD->isAnonymousNamespace())
316 return;
317 std::string Scope = printNamespaceScope(*NSD);
318 if (!Scope.empty())
319 ScopeRefsInFile = std::max(
320 ScopeRefsInFile, MainFileSignals->RelatedNamespaces.lookup(Scope));
321 }
322 }
323}
324
325void SymbolRelevanceSignals::merge(const CodeCompletionResult &SemaCCResult) {
326 if (SemaCCResult.Availability == CXAvailability_NotAvailable ||
327 SemaCCResult.Availability == CXAvailability_NotAccessible)
328 Forbidden = true;
329
330 if (SemaCCResult.Declaration) {
331 SemaSaysInScope = true;
332 // We boost things that have decls in the main file. We give a fixed score
333 // for all other declarations in sema as they are already included in the
334 // translation unit.
335 float DeclProximity = (hasDeclInMainFile(*SemaCCResult.Declaration) ||
336 hasUsingDeclInMainFile(SemaCCResult))
337 ? 1.0
338 : 0.6;
339 SemaFileProximityScore = std::max(DeclProximity, SemaFileProximityScore);
340 IsInstanceMember |= isInstanceMember(SemaCCResult.Declaration);
341 InBaseClass |= SemaCCResult.InBaseClass;
342 }
343
344 computeASTSignals(SemaCCResult);
345 // Declarations are scoped, others (like macros) are assumed global.
346 if (SemaCCResult.Declaration)
347 Scope = std::min(Scope, computeScope(SemaCCResult.Declaration));
348
349 NeedsFixIts = !SemaCCResult.FixIts.empty();
350}
351
352static float fileProximityScore(unsigned FileDistance) {
353 // Range: [0, 1]
354 // FileDistance = [0, 1, 2, 3, 4, .., FileDistance::Unreachable]
355 // Score = [1, 0.82, 0.67, 0.55, 0.45, .., 0]
356 if (FileDistance == FileDistance::Unreachable)
357 return 0;
358 // Assume approximately default options are used for sensible scoring.
359 return std::exp(FileDistance * -0.4f / FileDistanceOptions().UpCost);
360}
361
362static float scopeProximityScore(unsigned ScopeDistance) {
363 // Range: [0.6, 2].
364 // ScopeDistance = [0, 1, 2, 3, 4, 5, 6, 7, .., FileDistance::Unreachable]
365 // Score = [2.0, 1.55, 1.2, 0.93, 0.72, 0.65, 0.65, 0.65, .., 0.6]
366 if (ScopeDistance == FileDistance::Unreachable)
367 return 0.6f;
368 return std::max(0.65, 2.0 * std::pow(0.6, ScopeDistance / 2.0));
369}
370
371static std::optional<llvm::StringRef>
372wordMatching(llvm::StringRef Name, const llvm::StringSet<> *ContextWords) {
373 if (ContextWords)
374 for (const auto &Word : ContextWords->keys())
375 if (Name.contains_insensitive(Word))
376 return Word;
377 return std::nullopt;
378}
379
380SymbolRelevanceSignals::DerivedSignals
381SymbolRelevanceSignals::calculateDerivedSignals() const {
382 DerivedSignals Derived;
383 Derived.NameMatchesContext = wordMatching(Name, ContextWords).has_value();
384 Derived.FileProximityDistance = !FileProximityMatch || SymbolURI.empty()
385 ? FileDistance::Unreachable
386 : FileProximityMatch->distance(SymbolURI);
387 if (ScopeProximityMatch) {
388 // For global symbol, the distance is 0.
389 Derived.ScopeProximityDistance =
390 SymbolScope ? ScopeProximityMatch->distance(*SymbolScope) : 0;
391 }
392 return Derived;
393}
394
395float SymbolRelevanceSignals::evaluateHeuristics() const {
396 DerivedSignals Derived = calculateDerivedSignals();
397 float Score = 1;
398
399 if (Forbidden)
400 return 0;
401
402 Score *= NameMatch;
403
404 // File proximity scores are [0,1] and we translate them into a multiplier in
405 // the range from 1 to 3.
406 Score *= 1 + 2 * std::max(fileProximityScore(Derived.FileProximityDistance),
407 SemaFileProximityScore);
408
409 if (ScopeProximityMatch)
410 // Use a constant scope boost for sema results, as scopes of sema results
411 // can be tricky (e.g. class/function scope). Set to the max boost as we
412 // don't load top-level symbols from the preamble and sema results are
413 // always in the accessible scope.
414 Score *= SemaSaysInScope
415 ? 2.0
416 : scopeProximityScore(Derived.ScopeProximityDistance);
417
418 if (Derived.NameMatchesContext)
419 Score *= 1.5;
420
421 // Symbols like local variables may only be referenced within their scope.
422 // Conversely if we're in that scope, it's likely we'll reference them.
423 if (Query == CodeComplete) {
424 // The narrower the scope where a symbol is visible, the more likely it is
425 // to be relevant when it is available.
426 switch (Scope) {
427 case GlobalScope:
428 break;
429 case FileScope:
430 Score *= 1.5f;
431 break;
432 case ClassScope:
433 Score *= 2;
434 break;
435 case FunctionScope:
436 Score *= 4;
437 break;
438 }
439 } else {
440 // For non-completion queries, the wider the scope where a symbol is
441 // visible, the more likely it is to be relevant.
442 switch (Scope) {
443 case GlobalScope:
444 break;
445 case FileScope:
446 Score *= 0.5f;
447 break;
448 default:
449 // TODO: Handle other scopes as we start to use them for index results.
450 break;
451 }
452 }
453
454 if (TypeMatchesPreferred)
455 Score *= 5.0;
456
457 // Penalize non-instance members when they are accessed via a class instance.
458 if (!IsInstanceMember &&
459 (Context == CodeCompletionContext::CCC_DotMemberAccess ||
460 Context == CodeCompletionContext::CCC_ArrowMemberAccess)) {
461 Score *= 0.2f;
462 }
463
464 if (InBaseClass)
465 Score *= 0.5f;
466
467 // Penalize for FixIts.
468 if (NeedsFixIts)
469 Score *= 0.5f;
470
471 // Use a sigmoid style boosting function similar to `References`, which flats
472 // out nicely for large values. This avoids a sharp gradient for heavily
473 // referenced symbols. Use smaller gradient for ScopeRefsInFile since ideally
474 // MainFileRefs <= ScopeRefsInFile.
475 if (MainFileRefs >= 2) {
476 // E.g.: (2, 1.12), (9, 2.0), (48, 3.0).
477 float S = std::pow(MainFileRefs, -0.11);
478 Score *= 11.0 * (1 - S) / (1 + S) + 0.7;
479 }
480 if (ScopeRefsInFile >= 2) {
481 // E.g.: (2, 1.04), (14, 2.0), (109, 3.0), (400, 3.6).
482 float S = std::pow(ScopeRefsInFile, -0.10);
483 Score *= 10.0 * (1 - S) / (1 + S) + 0.7;
484 }
485
486 return Score;
487}
488
489llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
490 const SymbolRelevanceSignals &S) {
491 OS << llvm::formatv("=== Symbol relevance: {0}\n", S.evaluateHeuristics());
492 OS << llvm::formatv("\tName: {0}\n", S.Name);
493 OS << llvm::formatv("\tName match: {0}\n", S.NameMatch);
494 if (S.ContextWords)
495 OS << llvm::formatv(
496 "\tMatching context word: {0}\n",
497 wordMatching(S.Name, S.ContextWords).value_or("<none>"));
498 OS << llvm::formatv("\tForbidden: {0}\n", S.Forbidden);
499 OS << llvm::formatv("\tNeedsFixIts: {0}\n", S.NeedsFixIts);
500 OS << llvm::formatv("\tIsInstanceMember: {0}\n", S.IsInstanceMember);
501 OS << llvm::formatv("\tInBaseClass: {0}\n", S.InBaseClass);
502 OS << llvm::formatv("\tContext: {0}\n", getCompletionKindString(S.Context));
503 OS << llvm::formatv("\tQuery type: {0}\n", static_cast<int>(S.Query));
504 OS << llvm::formatv("\tScope: {0}\n", static_cast<int>(S.Scope));
505
506 OS << llvm::formatv("\tSymbol URI: {0}\n", S.SymbolURI);
507 OS << llvm::formatv("\tSymbol scope: {0}\n",
508 S.SymbolScope ? *S.SymbolScope : "<None>");
509
510 SymbolRelevanceSignals::DerivedSignals Derived = S.calculateDerivedSignals();
511 if (S.FileProximityMatch) {
512 unsigned Score = fileProximityScore(Derived.FileProximityDistance);
513 OS << llvm::formatv("\tIndex URI proximity: {0} (distance={1})\n", Score,
514 Derived.FileProximityDistance);
515 }
516 OS << llvm::formatv("\tSema file proximity: {0}\n", S.SemaFileProximityScore);
517
518 OS << llvm::formatv("\tSema says in scope: {0}\n", S.SemaSaysInScope);
519 if (S.ScopeProximityMatch)
520 OS << llvm::formatv("\tIndex scope boost: {0}\n",
521 scopeProximityScore(Derived.ScopeProximityDistance));
522
523 OS << llvm::formatv(
524 "\tType matched preferred: {0} (Context type: {1}, Symbol type: {2}\n",
525 S.TypeMatchesPreferred, S.HadContextType, S.HadSymbolType);
526
527 return OS;
528}
529
530float evaluateSymbolAndRelevance(float SymbolQuality, float SymbolRelevance) {
531 return SymbolQuality * SymbolRelevance;
532}
533
534// Produces an integer that sorts in the same order as F.
535// That is: a < b <==> encodeFloat(a) < encodeFloat(b).
536static uint32_t encodeFloat(float F) {
537 static_assert(std::numeric_limits<float>::is_iec559);
538 constexpr uint32_t TopBit = ~(~uint32_t{0} >> 1);
539
540 // Get the bits of the float. Endianness is the same as for integers.
541 uint32_t U = llvm::bit_cast<uint32_t>(F);
542 // IEEE 754 floats compare like sign-magnitude integers.
543 if (U & TopBit) // Negative float.
544 return 0 - U; // Map onto the low half of integers, order reversed.
545 return U + TopBit; // Positive floats map onto the high half of integers.
546}
547
548std::string sortText(float Score, llvm::StringRef Name) {
549 // We convert -Score to an integer, and hex-encode for readability.
550 // Example: [0.5, "foo"] -> "41000000foo"
551 std::string S;
552 llvm::raw_string_ostream OS(S);
553 llvm::write_hex(OS, encodeFloat(-Score), llvm::HexPrintStyle::Lower,
554 /*Width=*/2 * sizeof(Score));
555 OS << Name;
556 OS.flush();
557 return S;
558}
559
560llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
561 const SignatureQualitySignals &S) {
562 OS << llvm::formatv("=== Signature Quality:\n");
563 OS << llvm::formatv("\tNumber of parameters: {0}\n", S.NumberOfParameters);
564 OS << llvm::formatv("\tNumber of optional parameters: {0}\n",
565 S.NumberOfOptionalParameters);
566 OS << llvm::formatv("\tKind: {0}\n", S.Kind);
567 return OS;
568}
569
570} // namespace clangd
571} // namespace clang
572