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
20namespace clang {
21
22struct DeducedPack;
23class TemplateArgumentList;
24class Sema;
25
26namespace sema {
27
28/// \brief Provides information about an attempted template argument
29/// deduction, whose success or failure was described by a
30/// TemplateDeductionResult value.
31class 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
50public:
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.
57  SourceLocation getLocation() const {
58    return Loc;
59  }
60
61  /// \brief Take ownership of the deduced template argument list.
62  TemplateArgumentList *take() {
63    TemplateArgumentList *Result = Deduced;
64    Deduced = nullptr;
65    return Result;
66  }
67
68  /// \brief Take ownership of the SFINAE diagnostic.
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.
79  void reset(TemplateArgumentList *NewDeduced) {
80    Deduced = NewDeduced;
81  }
82
83  /// \brief Is a SFINAE diagnostic available?
84  bool hasSFINAEDiagnostic() const {
85    return HasSFINAEDiagnostic;
86  }
87
88  /// \brief Set the diagnostic which caused the SFINAE failure.
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
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.
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.
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.
173struct 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.
225struct 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
233  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.
246class 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
256public:
257  TemplateSpecCandidateSet(SourceLocation Loc) : Loc(Loc) {}
258  ~TemplateSpecCandidateSet() { destroyCandidates(); }
259
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;
267  iterator begin() { return Candidates.begin(); }
268  iterator end() { return Candidates.end(); }
269
270  size_t size() const { return Candidates.size(); }
271  bool empty() const { return Candidates.empty(); }
272
273  /// \brief Add a new candidate with NumConversions conversion sequence slots
274  /// to the overload set.
275  TemplateSpecCandidate &addCandidate() {
276    Candidates.emplace_back();
277    return Candidates.back();
278  }
279
280  void NoteCandidates(Sema &S, SourceLocation Loc);
281
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