SemaCXXScopeSpec.cpp revision 5cad1f74469d4d8b4fc51fe53a7837778aeb6107 
1//===--- SemaCXXScopeSpec.cpp - Semantic Analysis for C++ scope specifiers-===//
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//
10// This file implements C++ semantic analysis for scope specifiers.
11//
12//===----------------------------------------------------------------------===//
13
14#include "Sema.h"
15#include "clang/AST/ASTContext.h"
16#include "clang/AST/DeclTemplate.h"
17#include "clang/AST/NestedNameSpecifier.h"
18#include "clang/Parse/DeclSpec.h"
19#include "llvm/ADT/STLExtras.h"
20using namespace clang;
21
22/// \brief Compute the DeclContext that is associated with the given
23/// scope specifier.
24DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS) {
25  if (!SS.isSet() || SS.isInvalid())
26    return 0;
27
28  NestedNameSpecifier *NNS
29    = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
30  if (NNS->isDependent()) {
31    // If this nested-name-specifier refers to the current
32    // instantiation, return its DeclContext.
33    if (CXXRecordDecl *Record = getCurrentInstantiationOf(NNS))
34      return Record;
35    else
36      return 0;
37  }
38
39  switch (NNS->getKind()) {
40  case NestedNameSpecifier::Identifier:
41    assert(false && "Dependent nested-name-specifier has no DeclContext");
42    break;
43
44  case NestedNameSpecifier::Namespace:
45    return NNS->getAsNamespace();
46
47  case NestedNameSpecifier::TypeSpec:
48  case NestedNameSpecifier::TypeSpecWithTemplate: {
49    const TagType *Tag = NNS->getAsType()->getAs<TagType>();
50    assert(Tag && "Non-tag type in nested-name-specifier");
51    return Tag->getDecl();
52  } break;
53
54  case NestedNameSpecifier::Global:
55    return Context.getTranslationUnitDecl();
56  }
57
58  // Required to silence a GCC warning.
59  return 0;
60}
61
62bool Sema::isDependentScopeSpecifier(const CXXScopeSpec &SS) {
63  if (!SS.isSet() || SS.isInvalid())
64    return false;
65
66  NestedNameSpecifier *NNS
67    = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
68  return NNS->isDependent();
69}
70
71// \brief Determine whether this C++ scope specifier refers to an
72// unknown specialization, i.e., a dependent type that is not the
73// current instantiation.
74bool Sema::isUnknownSpecialization(const CXXScopeSpec &SS) {
75  if (!isDependentScopeSpecifier(SS))
76    return false;
77
78  NestedNameSpecifier *NNS
79    = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
80  return getCurrentInstantiationOf(NNS) == 0;
81}
82
83/// \brief If the given nested name specifier refers to the current
84/// instantiation, return the declaration that corresponds to that
85/// current instantiation (C++0x [temp.dep.type]p1).
86///
87/// \param NNS a dependent nested name specifier.
88CXXRecordDecl *Sema::getCurrentInstantiationOf(NestedNameSpecifier *NNS) {
89  assert(getLangOptions().CPlusPlus && "Only callable in C++");
90  assert(NNS->isDependent() && "Only dependent nested-name-specifier allowed");
91
92  QualType T = QualType(NNS->getAsType(), 0);
93  // If the nested name specifier does not refer to a type, then it
94  // does not refer to the current instantiation.
95  if (T.isNull())
96    return 0;
97
98  T = Context.getCanonicalType(T);
99
100  for (DeclContext *Ctx = CurContext; Ctx; Ctx = Ctx->getParent()) {
101    // If we've hit a namespace or the global scope, then the
102    // nested-name-specifier can't refer to the current instantiation.
103    if (Ctx->isFileContext())
104      return 0;
105
106    // Skip non-class contexts.
107    CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(Ctx);
108    if (!Record)
109      continue;
110
111    // If this record type is not dependent,
112    if (!Record->isDependentType())
113      return 0;
114
115    // C++ [temp.dep.type]p1:
116    //
117    //   In the definition of a class template, a nested class of a
118    //   class template, a member of a class template, or a member of a
119    //   nested class of a class template, a name refers to the current
120    //   instantiation if it is
121    //     -- the injected-class-name (9) of the class template or
122    //        nested class,
123    //     -- in the definition of a primary class template, the name
124    //        of the class template followed by the template argument
125    //        list of the primary template (as described below)
126    //        enclosed in <>,
127    //     -- in the definition of a nested class of a class template,
128    //        the name of the nested class referenced as a member of
129    //        the current instantiation, or
130    //     -- in the definition of a partial specialization, the name
131    //        of the class template followed by the template argument
132    //        list of the partial specialization enclosed in <>. If
133    //        the nth template parameter is a parameter pack, the nth
134    //        template argument is a pack expansion (14.6.3) whose
135    //        pattern is the name of the parameter pack. (FIXME)
136    //
137    // All of these options come down to having the
138    // nested-name-specifier type that is equivalent to the
139    // injected-class-name of one of the types that is currently in
140    // our context.
141    if (Context.getTypeDeclType(Record) == T)
142      return Record;
143
144    if (ClassTemplateDecl *Template = Record->getDescribedClassTemplate()) {
145      QualType InjectedClassName
146        = Template->getInjectedClassNameType(Context);
147      if (T == Context.getCanonicalType(InjectedClassName))
148        return Template->getTemplatedDecl();
149    }
150  }
151
152  return 0;
153}
154
155/// \brief Require that the context specified by SS be complete.
156///
157/// If SS refers to a type, this routine checks whether the type is
158/// complete enough (or can be made complete enough) for name lookup
159/// into the DeclContext. A type that is not yet completed can be
160/// considered "complete enough" if it is a class/struct/union/enum
161/// that is currently being defined. Or, if we have a type that names
162/// a class template specialization that is not a complete type, we
163/// will attempt to instantiate that class template.
164bool Sema::RequireCompleteDeclContext(const CXXScopeSpec &SS) {
165  if (!SS.isSet() || SS.isInvalid())
166    return false;
167
168  DeclContext *DC = computeDeclContext(SS);
169  if (TagDecl *Tag = dyn_cast<TagDecl>(DC)) {
170    // If we're currently defining this type, then lookup into the
171    // type is okay: don't complain that it isn't complete yet.
172    const TagType *TagT = Context.getTypeDeclType(Tag)->getAs<TagType>();
173    if (TagT->isBeingDefined())
174      return false;
175
176    // The type must be complete.
177    return RequireCompleteType(SS.getRange().getBegin(),
178                               Context.getTypeDeclType(Tag),
179                               diag::err_incomplete_nested_name_spec,
180                               SS.getRange());
181  }
182
183  return false;
184}
185
186/// ActOnCXXGlobalScopeSpecifier - Return the object that represents the
187/// global scope ('::').
188Sema::CXXScopeTy *Sema::ActOnCXXGlobalScopeSpecifier(Scope *S,
189                                                     SourceLocation CCLoc) {
190  return NestedNameSpecifier::GlobalSpecifier(Context);
191}
192
193/// ActOnCXXNestedNameSpecifier - Called during parsing of a
194/// nested-name-specifier. e.g. for "foo::bar::" we parsed "foo::" and now
195/// we want to resolve "bar::". 'SS' is empty or the previously parsed
196/// nested-name part ("foo::"), 'IdLoc' is the source location of 'bar',
197/// 'CCLoc' is the location of '::' and 'II' is the identifier for 'bar'.
198/// Returns a CXXScopeTy* object representing the C++ scope.
199Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S,
200                                                    const CXXScopeSpec &SS,
201                                                    SourceLocation IdLoc,
202                                                    SourceLocation CCLoc,
203                                                    IdentifierInfo &II) {
204  NestedNameSpecifier *Prefix
205    = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
206
207  // If the prefix already refers to an unknown specialization, there
208  // is no name lookup to perform. Just build the resulting
209  // nested-name-specifier.
210  if (Prefix && isUnknownSpecialization(SS))
211    return NestedNameSpecifier::Create(Context, Prefix, &II);
212
213  NamedDecl *SD = LookupParsedName(S, &SS, &II, LookupNestedNameSpecifierName);
214
215  if (SD) {
216    if (NamespaceDecl *Namespace = dyn_cast<NamespaceDecl>(SD))
217      return NestedNameSpecifier::Create(Context, Prefix, Namespace);
218
219    if (TypeDecl *Type = dyn_cast<TypeDecl>(SD)) {
220      // Determine whether we have a class (or, in C++0x, an enum) or
221      // a typedef thereof. If so, build the nested-name-specifier.
222      QualType T = Context.getTypeDeclType(Type);
223      bool AcceptableType = false;
224      if (T->isDependentType())
225        AcceptableType = true;
226      else if (TypedefDecl *TD = dyn_cast<TypedefDecl>(SD)) {
227        if (TD->getUnderlyingType()->isRecordType() ||
228            (getLangOptions().CPlusPlus0x &&
229             TD->getUnderlyingType()->isEnumeralType()))
230          AcceptableType = true;
231      } else if (isa<RecordDecl>(Type) ||
232                 (getLangOptions().CPlusPlus0x && isa<EnumDecl>(Type)))
233        AcceptableType = true;
234
235      if (AcceptableType)
236        return NestedNameSpecifier::Create(Context, Prefix, false,
237                                           T.getTypePtr());
238    }
239
240    if (NamespaceAliasDecl *Alias = dyn_cast<NamespaceAliasDecl>(SD))
241      return NestedNameSpecifier::Create(Context, Prefix,
242                                         Alias->getNamespace());
243
244    // Fall through to produce an error: we found something that isn't
245    // a class or a namespace.
246  }
247
248  // If we didn't find anything during our lookup, try again with
249  // ordinary name lookup, which can help us produce better error
250  // messages.
251  if (!SD)
252    SD = LookupParsedName(S, &SS, &II, LookupOrdinaryName);
253  unsigned DiagID;
254  if (SD)
255    DiagID = diag::err_expected_class_or_namespace;
256  else if (SS.isSet())
257    DiagID = diag::err_typecheck_no_member;
258  else
259    DiagID = diag::err_undeclared_var_use;
260
261  if (SS.isSet())
262    Diag(IdLoc, DiagID) << &II << SS.getRange();
263  else
264    Diag(IdLoc, DiagID) << &II;
265
266  return 0;
267}
268
269Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S,
270                                                    const CXXScopeSpec &SS,
271                                                    TypeTy *Ty,
272                                                    SourceRange TypeRange,
273                                                    SourceLocation CCLoc) {
274  NestedNameSpecifier *Prefix
275    = static_cast<NestedNameSpecifier *>(SS.getScopeRep());
276  QualType T = QualType::getFromOpaquePtr(Ty);
277  return NestedNameSpecifier::Create(Context, Prefix, /*FIXME:*/false,
278                                     T.getTypePtr());
279}
280
281/// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
282/// scope or nested-name-specifier) is parsed, part of a declarator-id.
283/// After this method is called, according to [C++ 3.4.3p3], names should be
284/// looked up in the declarator-id's scope, until the declarator is parsed and
285/// ActOnCXXExitDeclaratorScope is called.
286/// The 'SS' should be a non-empty valid CXXScopeSpec.
287void Sema::ActOnCXXEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
288  assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
289  EnterDeclaratorContext(S, computeDeclContext(SS));
290}
291
292/// ActOnCXXExitDeclaratorScope - Called when a declarator that previously
293/// invoked ActOnCXXEnterDeclaratorScope(), is finished. 'SS' is the same
294/// CXXScopeSpec that was passed to ActOnCXXEnterDeclaratorScope as well.
295/// Used to indicate that names should revert to being looked up in the
296/// defining scope.
297void Sema::ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
298  assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
299  assert(S->getEntity() == computeDeclContext(SS) && "Context imbalance!");
300  ExitDeclaratorContext(S);
301}
302