1 //===- TemplateDeduction.h - C++ template argument deduction ----*- C++ -*-===/
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //===----------------------------------------------------------------------===/
8 //
9 //  This file provides types used with Sema's template argument deduction
10 // routines.
11 //
12 //===----------------------------------------------------------------------===/
13 #ifndef LLVM_CLANG_SEMA_TEMPLATEDEDUCTION_H
14 #define LLVM_CLANG_SEMA_TEMPLATEDEDUCTION_H
15 
16 #include "clang/AST/DeclTemplate.h"
17 #include "clang/Basic/PartialDiagnostic.h"
18 #include "llvm/ADT/SmallVector.h"
19 
20 namespace clang {
21 
22 struct DeducedPack;
23 class TemplateArgumentList;
24 class Sema;
25 
26 namespace sema {
27 
28 /// \brief Provides information about an attempted template argument
29 /// deduction, whose success or failure was described by a
30 /// TemplateDeductionResult value.
31 class TemplateDeductionInfo {
32   /// \brief The deduced template argument list.
33   ///
34   TemplateArgumentList *Deduced;
35 
36   /// \brief The source location at which template argument
37   /// deduction is occurring.
38   SourceLocation Loc;
39 
40   /// \brief Have we suppressed an error during deduction?
41   bool HasSFINAEDiagnostic;
42 
43   /// \brief Warnings (and follow-on notes) that were suppressed due to
44   /// SFINAE while performing template argument deduction.
45   SmallVector<PartialDiagnosticAt, 4> SuppressedDiagnostics;
46 
47   TemplateDeductionInfo(const TemplateDeductionInfo &) = delete;
48   void operator=(const TemplateDeductionInfo &) = delete;
49 
50 public:
TemplateDeductionInfo(SourceLocation Loc)51   TemplateDeductionInfo(SourceLocation Loc)
52     : Deduced(nullptr), Loc(Loc), HasSFINAEDiagnostic(false),
53       Expression(nullptr) {}
54 
55   /// \brief Returns the location at which template argument is
56   /// occurring.
getLocation()57   SourceLocation getLocation() const {
58     return Loc;
59   }
60 
61   /// \brief Take ownership of the deduced template argument list.
take()62   TemplateArgumentList *take() {
63     TemplateArgumentList *Result = Deduced;
64     Deduced = nullptr;
65     return Result;
66   }
67 
68   /// \brief Take ownership of the SFINAE diagnostic.
takeSFINAEDiagnostic(PartialDiagnosticAt & PD)69   void takeSFINAEDiagnostic(PartialDiagnosticAt &PD) {
70     assert(HasSFINAEDiagnostic);
71     PD.first = SuppressedDiagnostics.front().first;
72     PD.second.swap(SuppressedDiagnostics.front().second);
73     SuppressedDiagnostics.clear();
74     HasSFINAEDiagnostic = false;
75   }
76 
77   /// \brief Provide a new template argument list that contains the
78   /// results of template argument deduction.
reset(TemplateArgumentList * NewDeduced)79   void reset(TemplateArgumentList *NewDeduced) {
80     Deduced = NewDeduced;
81   }
82 
83   /// \brief Is a SFINAE diagnostic available?
hasSFINAEDiagnostic()84   bool hasSFINAEDiagnostic() const {
85     return HasSFINAEDiagnostic;
86   }
87 
88   /// \brief Set the diagnostic which caused the SFINAE failure.
addSFINAEDiagnostic(SourceLocation Loc,PartialDiagnostic PD)89   void addSFINAEDiagnostic(SourceLocation Loc, PartialDiagnostic PD) {
90     // Only collect the first diagnostic.
91     if (HasSFINAEDiagnostic)
92       return;
93     SuppressedDiagnostics.clear();
94     SuppressedDiagnostics.emplace_back(Loc, std::move(PD));
95     HasSFINAEDiagnostic = true;
96   }
97 
98   /// \brief Add a new diagnostic to the set of diagnostics
addSuppressedDiagnostic(SourceLocation Loc,PartialDiagnostic PD)99   void addSuppressedDiagnostic(SourceLocation Loc,
100                                PartialDiagnostic PD) {
101     if (HasSFINAEDiagnostic)
102       return;
103     SuppressedDiagnostics.emplace_back(Loc, std::move(PD));
104   }
105 
106   /// \brief Iterator over the set of suppressed diagnostics.
107   typedef SmallVectorImpl<PartialDiagnosticAt>::const_iterator
108     diag_iterator;
109 
110   /// \brief Returns an iterator at the beginning of the sequence of suppressed
111   /// diagnostics.
diag_begin()112   diag_iterator diag_begin() const { return SuppressedDiagnostics.begin(); }
113 
114   /// \brief Returns an iterator at the end of the sequence of suppressed
115   /// diagnostics.
diag_end()116   diag_iterator diag_end() const { return SuppressedDiagnostics.end(); }
117 
118   /// \brief The template parameter to which a template argument
119   /// deduction failure refers.
120   ///
121   /// Depending on the result of template argument deduction, this
122   /// template parameter may have different meanings:
123   ///
124   ///   TDK_Incomplete: this is the first template parameter whose
125   ///   corresponding template argument was not deduced.
126   ///
127   ///   TDK_Inconsistent: this is the template parameter for which
128   ///   two different template argument values were deduced.
129   TemplateParameter Param;
130 
131   /// \brief The first template argument to which the template
132   /// argument deduction failure refers.
133   ///
134   /// Depending on the result of the template argument deduction,
135   /// this template argument may have different meanings:
136   ///
137   ///   TDK_Inconsistent: this argument is the first value deduced
138   ///   for the corresponding template parameter.
139   ///
140   ///   TDK_SubstitutionFailure: this argument is the template
141   ///   argument we were instantiating when we encountered an error.
142   ///
143   ///   TDK_NonDeducedMismatch: this is the component of the 'parameter'
144   ///   of the deduction, directly provided in the source code.
145   TemplateArgument FirstArg;
146 
147   /// \brief The second template argument to which the template
148   /// argument deduction failure refers.
149   ///
150   ///   TDK_NonDeducedMismatch: this is the mismatching component of the
151   ///   'argument' of the deduction, from which we are deducing arguments.
152   ///
153   /// FIXME: Finish documenting this.
154   TemplateArgument SecondArg;
155 
156   /// \brief The expression which caused a deduction failure.
157   ///
158   ///   TDK_FailedOverloadResolution: this argument is the reference to
159   ///   an overloaded function which could not be resolved to a specific
160   ///   function.
161   Expr *Expression;
162 
163   /// \brief Information on packs that we're currently expanding.
164   ///
165   /// FIXME: This should be kept internal to SemaTemplateDeduction.
166   SmallVector<DeducedPack *, 8> PendingDeducedPacks;
167 };
168 
169 } // end namespace sema
170 
171 /// A structure used to record information about a failed
172 /// template argument deduction, for diagnosis.
173 struct DeductionFailureInfo {
174   /// A Sema::TemplateDeductionResult.
175   unsigned Result : 8;
176 
177   /// \brief Indicates whether a diagnostic is stored in Diagnostic.
178   unsigned HasDiagnostic : 1;
179 
180   /// \brief Opaque pointer containing additional data about
181   /// this deduction failure.
182   void *Data;
183 
184   /// \brief A diagnostic indicating why deduction failed.
185   union {
186     void *Align;
187     char Diagnostic[sizeof(PartialDiagnosticAt)];
188   };
189 
190   /// \brief Retrieve the diagnostic which caused this deduction failure,
191   /// if any.
192   PartialDiagnosticAt *getSFINAEDiagnostic();
193 
194   /// \brief Retrieve the template parameter this deduction failure
195   /// refers to, if any.
196   TemplateParameter getTemplateParameter();
197 
198   /// \brief Retrieve the template argument list associated with this
199   /// deduction failure, if any.
200   TemplateArgumentList *getTemplateArgumentList();
201 
202   /// \brief Return the first template argument this deduction failure
203   /// refers to, if any.
204   const TemplateArgument *getFirstArg();
205 
206   /// \brief Return the second template argument this deduction failure
207   /// refers to, if any.
208   const TemplateArgument *getSecondArg();
209 
210   /// \brief Return the expression this deduction failure refers to,
211   /// if any.
212   Expr *getExpr();
213 
214   /// \brief Free any memory associated with this deduction failure.
215   void Destroy();
216 };
217 
218 /// TemplateSpecCandidate - This is a generalization of OverloadCandidate
219 /// which keeps track of template argument deduction failure info, when
220 /// handling explicit specializations (and instantiations) of templates
221 /// beyond function overloading.
222 /// For now, assume that the candidates are non-matching specializations.
223 /// TODO: In the future, we may need to unify/generalize this with
224 /// OverloadCandidate.
225 struct TemplateSpecCandidate {
226   /// Specialization - The actual specialization that this candidate
227   /// represents. When NULL, this may be a built-in candidate.
228   Decl *Specialization;
229 
230   /// Template argument deduction info
231   DeductionFailureInfo DeductionFailure;
232 
setTemplateSpecCandidate233   void set(Decl *Spec, DeductionFailureInfo Info) {
234     Specialization = Spec;
235     DeductionFailure = Info;
236   }
237 
238   /// Diagnose a template argument deduction failure.
239   void NoteDeductionFailure(Sema &S);
240 };
241 
242 /// TemplateSpecCandidateSet - A set of generalized overload candidates,
243 /// used in template specializations.
244 /// TODO: In the future, we may need to unify/generalize this with
245 /// OverloadCandidateSet.
246 class TemplateSpecCandidateSet {
247   SmallVector<TemplateSpecCandidate, 16> Candidates;
248   SourceLocation Loc;
249 
250   TemplateSpecCandidateSet(
251       const TemplateSpecCandidateSet &) = delete;
252   void operator=(const TemplateSpecCandidateSet &) = delete;
253 
254   void destroyCandidates();
255 
256 public:
TemplateSpecCandidateSet(SourceLocation Loc)257   TemplateSpecCandidateSet(SourceLocation Loc) : Loc(Loc) {}
~TemplateSpecCandidateSet()258   ~TemplateSpecCandidateSet() { destroyCandidates(); }
259 
getLocation()260   SourceLocation getLocation() const { return Loc; }
261 
262   /// \brief Clear out all of the candidates.
263   /// TODO: This may be unnecessary.
264   void clear();
265 
266   typedef SmallVector<TemplateSpecCandidate, 16>::iterator iterator;
begin()267   iterator begin() { return Candidates.begin(); }
end()268   iterator end() { return Candidates.end(); }
269 
size()270   size_t size() const { return Candidates.size(); }
empty()271   bool empty() const { return Candidates.empty(); }
272 
273   /// \brief Add a new candidate with NumConversions conversion sequence slots
274   /// to the overload set.
addCandidate()275   TemplateSpecCandidate &addCandidate() {
276     Candidates.emplace_back();
277     return Candidates.back();
278   }
279 
280   void NoteCandidates(Sema &S, SourceLocation Loc);
281 
NoteCandidates(Sema & S,SourceLocation Loc)282   void NoteCandidates(Sema &S, SourceLocation Loc) const {
283     const_cast<TemplateSpecCandidateSet *>(this)->NoteCandidates(S, Loc);
284   }
285 };
286 
287 } // end namespace clang
288 
289 #endif
290