Make UsingShadowDecls redeclarable. This fixes some visibility problems with

modules.

With this fixed, I no longer see any test regressions in the libc++ test suite
when enabling a single-module module.map for libc++ (other than issues with my
system headers).

llvm-svn: 193219

Author: zygoloid

clang/include/clang/AST/DeclCXX.h

@@ -2676,7 +2676,7 @@ class NamespaceAliasDecl : public NamedDecl {
 ///                 // Also creates a UsingShadowDecl for A::foo() in B
 /// }
 /// \endcode
-class UsingShadowDecl : public NamedDecl {
+class UsingShadowDecl : public NamedDecl, public Redeclarable<UsingShadowDecl> {
   virtual void anchor();
 
   /// The referenced declaration.
@@ -2699,6 +2699,17 @@ class UsingShadowDecl : public NamedDecl {
     setImplicit();
   }
 
+  typedef Redeclarable<UsingShadowDecl> redeclarable_base;
+  virtual UsingShadowDecl *getNextRedeclaration() {
+    return RedeclLink.getNext();
+  }
+  virtual UsingShadowDecl *getPreviousDeclImpl() {
+    return getPreviousDecl();
+  }
+  virtual UsingShadowDecl *getMostRecentDeclImpl() {
+    return getMostRecentDecl();
+  }
+
 public:
   static UsingShadowDecl *Create(ASTContext &C, DeclContext *DC,
                                  SourceLocation Loc, UsingDecl *Using,
@@ -2707,7 +2718,20 @@ class UsingShadowDecl : public NamedDecl {
   }
 
   static UsingShadowDecl *CreateDeserialized(ASTContext &C, unsigned ID);
-  
+
+  typedef redeclarable_base::redecl_iterator redecl_iterator;
+  using redeclarable_base::redecls_begin;
+  using redeclarable_base::redecls_end;
+  using redeclarable_base::getPreviousDecl;
+  using redeclarable_base::getMostRecentDecl;
+
+  virtual UsingShadowDecl *getCanonicalDecl() {
+    return getFirstDecl();
+  }
+  virtual const UsingShadowDecl *getCanonicalDecl() const {
+    return getFirstDecl();
+  }
+
   /// \brief Gets the underlying declaration which has been brought into the
   /// local scope.
   NamedDecl *getTargetDecl() const { return Underlying; }

clang/include/clang/Sema/Sema.h

@@ -3640,9 +3640,11 @@ class Sema {
 
   void HideUsingShadowDecl(Scope *S, UsingShadowDecl *Shadow);
   bool CheckUsingShadowDecl(UsingDecl *UD, NamedDecl *Target,
-                            const LookupResult &PreviousDecls);
+                            const LookupResult &PreviousDecls,
+                            UsingShadowDecl *&PrevShadow);
   UsingShadowDecl *BuildUsingShadowDecl(Scope *S, UsingDecl *UD,
-                                        NamedDecl *Target);
+                                        NamedDecl *Target,
+                                        UsingShadowDecl *PrevDecl);
 
   bool CheckUsingDeclRedeclaration(SourceLocation UsingLoc,
                                    bool HasTypenameKeyword,

clang/lib/Sema/SemaDeclCXX.cpp

@@ -7073,20 +7073,15 @@ Decl *Sema::ActOnUsingDeclaration(Scope *S,
 /// \brief Determine whether a using declaration considers the given
 /// declarations as "equivalent", e.g., if they are redeclarations of
 /// the same entity or are both typedefs of the same type.
-static bool 
-IsEquivalentForUsingDecl(ASTContext &Context, NamedDecl *D1, NamedDecl *D2,
-                         bool &SuppressRedeclaration) {
-  if (D1->getCanonicalDecl() == D2->getCanonicalDecl()) {
-    SuppressRedeclaration = false;
+static bool
+IsEquivalentForUsingDecl(ASTContext &Context, NamedDecl *D1, NamedDecl *D2) {
+  if (D1->getCanonicalDecl() == D2->getCanonicalDecl())
     return true;
-  }
 
   if (TypedefNameDecl *TD1 = dyn_cast<TypedefNameDecl>(D1))
-    if (TypedefNameDecl *TD2 = dyn_cast<TypedefNameDecl>(D2)) {
-      SuppressRedeclaration = true;
+    if (TypedefNameDecl *TD2 = dyn_cast<TypedefNameDecl>(D2))
       return Context.hasSameType(TD1->getUnderlyingType(),
                                  TD2->getUnderlyingType());
-    }
 
   return false;
 }
@@ -7095,7 +7090,8 @@ IsEquivalentForUsingDecl(ASTContext &Context, NamedDecl *D1, NamedDecl *D2,
 /// Determines whether to create a using shadow decl for a particular
 /// decl, given the set of decls existing prior to this using lookup.
 bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
-                                const LookupResult &Previous) {
+                                const LookupResult &Previous,
+                                UsingShadowDecl *&PrevShadow) {
   // Diagnose finding a decl which is not from a base class of the
   // current class.  We do this now because there are cases where this
   // function will silently decide not to build a shadow decl, which
@@ -7155,16 +7151,22 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
   // FIXME: but we might be increasing its access, in which case we
   // should redeclare it.
   NamedDecl *NonTag = 0, *Tag = 0;
+  bool FoundEquivalentDecl = false;
   for (LookupResult::iterator I = Previous.begin(), E = Previous.end();
          I != E; ++I) {
     NamedDecl *D = (*I)->getUnderlyingDecl();
-    bool Result;
-    if (IsEquivalentForUsingDecl(Context, D, Target, Result))
-      return Result;
+    if (IsEquivalentForUsingDecl(Context, D, Target)) {
+      if (UsingShadowDecl *Shadow = dyn_cast<UsingShadowDecl>(*I))
+        PrevShadow = Shadow;
+      FoundEquivalentDecl = true;
+    }
 
     (isa<TagDecl>(D) ? Tag : NonTag) = D;
   }
 
+  if (FoundEquivalentDecl)
+    return false;
+
   if (Target->isFunctionOrFunctionTemplate()) {
     FunctionDecl *FD;
     if (isa<FunctionTemplateDecl>(Target))
@@ -7223,24 +7225,27 @@ bool Sema::CheckUsingShadowDecl(UsingDecl *Using, NamedDecl *Orig,
 /// Builds a shadow declaration corresponding to a 'using' declaration.
 UsingShadowDecl *Sema::BuildUsingShadowDecl(Scope *S,
                                             UsingDecl *UD,
-                                            NamedDecl *Orig) {
+                                            NamedDecl *Orig,
+                                            UsingShadowDecl *PrevDecl) {
 
   // If we resolved to another shadow declaration, just coalesce them.
   NamedDecl *Target = Orig;
   if (isa<UsingShadowDecl>(Target)) {
     Target = cast<UsingShadowDecl>(Target)->getTargetDecl();
     assert(!isa<UsingShadowDecl>(Target) && "nested shadow declaration");
   }
-  
+
   UsingShadowDecl *Shadow
     = UsingShadowDecl::Create(Context, CurContext,
                               UD->getLocation(), UD, Target);
   UD->addShadowDecl(Shadow);
-  
+
   Shadow->setAccess(UD->getAccess());
   if (Orig->isInvalidDecl() || UD->isInvalidDecl())
     Shadow->setInvalidDecl();
-  
+
+  Shadow->setPreviousDecl(PrevDecl);
+
   if (S)
     PushOnScopeChains(Shadow, S);
   else
@@ -7504,8 +7509,9 @@ NamedDecl *Sema::BuildUsingDeclaration(Scope *S, AccessSpecifier AS,
   }
 
   for (LookupResult::iterator I = R.begin(), E = R.end(); I != E; ++I) {
-    if (!CheckUsingShadowDecl(UD, *I, Previous))
-      BuildUsingShadowDecl(S, UD, *I);
+    UsingShadowDecl *PrevDecl = 0;
+    if (!CheckUsingShadowDecl(UD, *I, Previous, PrevDecl))
+      BuildUsingShadowDecl(S, UD, *I, PrevDecl);
   }
 
   return UD;

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -2152,19 +2152,22 @@ Decl *TemplateDeclInstantiator::VisitUsingDecl(UsingDecl *D) {
          I != E; ++I) {
     UsingShadowDecl *Shadow = *I;
     NamedDecl *InstTarget =
-      cast_or_null<NamedDecl>(SemaRef.FindInstantiatedDecl(
-                                                          Shadow->getLocation(),
-                                                        Shadow->getTargetDecl(),
-                                                           TemplateArgs));
+        cast_or_null<NamedDecl>(SemaRef.FindInstantiatedDecl(
+            Shadow->getLocation(), Shadow->getTargetDecl(), TemplateArgs));
     if (!InstTarget)
       return 0;
 
-    if (CheckRedeclaration &&
-        SemaRef.CheckUsingShadowDecl(NewUD, InstTarget, Prev))
-      continue;
+    UsingShadowDecl *PrevDecl = 0;
+    if (CheckRedeclaration) {
+      if (SemaRef.CheckUsingShadowDecl(NewUD, InstTarget, Prev, PrevDecl))
+        continue;
+    } else if (UsingShadowDecl *OldPrev = Shadow->getPreviousDecl()) {
+      PrevDecl = cast_or_null<UsingShadowDecl>(SemaRef.FindInstantiatedDecl(
+          Shadow->getLocation(), OldPrev, TemplateArgs));
+    }
 
-    UsingShadowDecl *InstShadow
-      = SemaRef.BuildUsingShadowDecl(/*Scope*/ 0, NewUD, InstTarget);
+    UsingShadowDecl *InstShadow =
+        SemaRef.BuildUsingShadowDecl(/*Scope*/0, NewUD, InstTarget, PrevDecl);
     SemaRef.Context.setInstantiatedFromUsingShadowDecl(InstShadow, Shadow);
 
     if (isFunctionScope)

clang/lib/Serialization/ASTCommon.cpp

@@ -165,6 +165,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::CXXConstructor:
   case Decl::CXXDestructor:
   case Decl::CXXConversion:
+  case Decl::UsingShadow:
   case Decl::Var:
   case Decl::FunctionTemplate:
   case Decl::ClassTemplate:
@@ -192,7 +193,6 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::NonTypeTemplateParm:
   case Decl::TemplateTemplateParm:
   case Decl::Using:
-  case Decl::UsingShadow:
   case Decl::ObjCMethod:
   case Decl::ObjCCategory:
   case Decl::ObjCCategoryImpl:

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -1134,12 +1134,14 @@ void ASTDeclReader::VisitUsingDecl(UsingDecl *D) {
 }
 
 void ASTDeclReader::VisitUsingShadowDecl(UsingShadowDecl *D) {
+  RedeclarableResult Redecl = VisitRedeclarable(D);
   VisitNamedDecl(D);
   D->setTargetDecl(ReadDeclAs<NamedDecl>(Record, Idx));
   D->UsingOrNextShadow = ReadDeclAs<NamedDecl>(Record, Idx);
   UsingShadowDecl *Pattern = ReadDeclAs<UsingShadowDecl>(Record, Idx);
   if (Pattern)
     Reader.getContext().setInstantiatedFromUsingShadowDecl(D, Pattern);
+  mergeRedeclarable(D, Redecl);
 }
 
 void ASTDeclReader::VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
@@ -2151,6 +2153,12 @@ static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
     // FIXME: Also check the value is odr-equivalent.
     return true;
 
+  // Using shadow declarations with the same target match.
+  if (UsingShadowDecl *USX = dyn_cast<UsingShadowDecl>(X)) {
+    UsingShadowDecl *USY = cast<UsingShadowDecl>(Y);
+    return USX->getTargetDecl() == USY->getTargetDecl();
+  }
+
   // FIXME: Many other cases to implement.
   return false;
 }
@@ -2258,6 +2266,8 @@ void ASTDeclReader::attachPreviousDecl(Decl *D, Decl *previous) {
     VD->RedeclLink.setNext(cast<VarDecl>(previous));
   } else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {
     TD->RedeclLink.setNext(cast<TypedefNameDecl>(previous));
+  } else if (UsingShadowDecl *USD = dyn_cast<UsingShadowDecl>(D)) {
+    USD->RedeclLink.setNext(cast<UsingShadowDecl>(previous));
   } else if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
     ID->RedeclLink.setNext(cast<ObjCInterfaceDecl>(previous));
   } else if (ObjCProtocolDecl *PD = dyn_cast<ObjCProtocolDecl>(D)) {
@@ -2285,7 +2295,7 @@ void ASTDeclReader::attachLatestDecl(Decl *D, Decl *Latest) {
     TD->RedeclLink
       = Redeclarable<TagDecl>::LatestDeclLink(cast<TagDecl>(Latest));
   } else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
-    FD->RedeclLink 
+    FD->RedeclLink
       = Redeclarable<FunctionDecl>::LatestDeclLink(cast<FunctionDecl>(Latest));
   } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
     VD->RedeclLink
@@ -2294,6 +2304,10 @@ void ASTDeclReader::attachLatestDecl(Decl *D, Decl *Latest) {
     TD->RedeclLink
       = Redeclarable<TypedefNameDecl>::LatestDeclLink(
                                                 cast<TypedefNameDecl>(Latest));
+  } else if (UsingShadowDecl *USD = dyn_cast<UsingShadowDecl>(D)) {
+    USD->RedeclLink
+      = Redeclarable<UsingShadowDecl>::LatestDeclLink(
+                                             cast<UsingShadowDecl>(Latest));
   } else if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D)) {
     ID->RedeclLink
       = Redeclarable<ObjCInterfaceDecl>::LatestDeclLink(

clang/lib/Serialization/ASTWriterDecl.cpp

@@ -938,6 +938,7 @@ void ASTDeclWriter::VisitUsingDecl(UsingDecl *D) {
 }
 
 void ASTDeclWriter::VisitUsingShadowDecl(UsingShadowDecl *D) {
+  VisitRedeclarable(D);
   VisitNamedDecl(D);
   Writer.AddDeclRef(D->getTargetDecl(), Record);
   Writer.AddDeclRef(D->UsingOrNextShadow, Record);

clang/test/Modules/Inputs/module.map

@@ -258,3 +258,8 @@ module warning {
 module initializer_list {
   header "initializer_list"
 }
+
+module using_decl {
+  module a { header "using-decl-a.h" export * }
+  module b { header "using-decl-b.h" export * }
+}

clang/test/Modules/Inputs/using-decl-a.h

@@ -0,0 +1,10 @@
+typedef int using_decl_type;
+int using_decl_var;
+
+namespace UsingDecl {
+  using ::using_decl_type;
+  using ::using_decl_var;
+
+  namespace A { typedef int inner; }
+  using A::inner;
+}

clang/test/Modules/Inputs/using-decl-b.h

@@ -0,0 +1,11 @@
+namespace UsingDecl {
+  namespace B { typedef int inner; }
+  using B::inner;
+}
+
+#include "using-decl-a.h"
+
+namespace UsingDecl {
+  using ::using_decl_type;
+  using ::using_decl_var;
+}

clang/test/Modules/using-decl.cpp

@@ -0,0 +1,8 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodules-cache-path=%t -I %S/Inputs %s -verify
+
+@import using_decl.a;
+
+// expected-no-diagnostics
+UsingDecl::using_decl_type x = UsingDecl::using_decl_var;
+UsingDecl::inner y = x;