Implement support for dependent Microsoft __if_exists/__if_not_exists

statements. As noted in the documentation for the AST node, the
semantics of __if_exists/__if_not_exists are somewhat different from
the way Visual C++ implements them, because our parsed-template
representation can't accommodate VC++ semantics without serious
contortions. Hopefully this implementation is "good enough".


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142901 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 118 insertions, 8 deletions

diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index c4571c96d0..2726906c1b 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -4665,18 +4665,18 @@ StmtResult Sema::ActOnFinishFullStmt(Stmt *FullStmt) {
   return MaybeCreateStmtWithCleanups(FullStmt);
 }
 
-Sema::IfExistsResult Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
-                                                        CXXScopeSpec &SS,
-                                                        UnqualifiedId &Name) {
-  DeclarationNameInfo TargetNameInfo = GetNameFromUnqualifiedId(Name);
+Sema::IfExistsResult 
+Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
+                                   CXXScopeSpec &SS,
+                                   const DeclarationNameInfo &TargetNameInfo) {
   DeclarationName TargetName = TargetNameInfo.getName();
   if (!TargetName)
     return IER_DoesNotExist;
-
+  
   // If the name itself is dependent, then the result is dependent.
   if (TargetName.isDependentName())
     return IER_Dependent;
-      
+  
   // Do the redeclaration lookup in the current scope.
   LookupResult R(*this, TargetNameInfo, Sema::LookupAnyName,
                  Sema::NotForRedeclaration);
@@ -4697,5 +4697,13 @@ Sema::IfExistsResult Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
     return IER_Dependent;
   }
   
-  return IER_DoesNotExist;
+  return IER_DoesNotExist;  
 }
+
+Sema::IfExistsResult Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
+                                                        CXXScopeSpec &SS,
+                                                        UnqualifiedId &Name) {
+  DeclarationNameInfo TargetNameInfo = GetNameFromUnqualifiedId(Name);
+  return CheckMicrosoftIfExistsSymbol(S, SS, TargetNameInfo);
+}
+
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 5351896204..3297c0641f 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -2484,3 +2484,26 @@ Sema::ActOnSEHFinallyBlock(SourceLocation Loc,
   assert(Block);
   return Owned(SEHFinallyStmt::Create(Context,Loc,Block));
 }
+
+StmtResult Sema::BuildMSDependentExistsStmt(SourceLocation KeywordLoc,
+                                            bool IsIfExists,
+                                            NestedNameSpecifierLoc QualifierLoc,
+                                            DeclarationNameInfo NameInfo,
+                                            Stmt *Nested)
+{
+  return new (Context) MSDependentExistsStmt(KeywordLoc, IsIfExists,
+                                             QualifierLoc, NameInfo, 
+                                             cast<CompoundStmt>(Nested));
+}
+
+
+StmtResult Sema::ActOnMSDependentExistsStmt(SourceLocation KeywordLoc, 
+                                            bool IsIfExists,
+                                            CXXScopeSpec &SS, 
+                                            UnqualifiedId &Name,
+                                            Stmt *Nested) {
+  return BuildMSDependentExistsStmt(KeywordLoc, IsIfExists, 
+                                    SS.getWithLocInContext(Context),
+                                    GetNameFromUnqualifiedId(Name),
+                                    Nested);
+}
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index b4073eb650..dde8a974c9 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -1291,7 +1291,20 @@ public:
     return getSema().BuildCXXForRangeStmt(ForLoc, ColonLoc, Range, BeginEnd,
                                           Cond, Inc, LoopVar, RParenLoc);
   }
-  
+
+  /// \brief Build a new C++0x range-based for statement.
+  ///
+  /// By default, performs semantic analysis to build the new statement.
+  /// Subclasses may override this routine to provide different behavior.
+  StmtResult RebuildMSDependentExistsStmt(SourceLocation KeywordLoc, 
+                                          bool IsIfExists,
+                                          NestedNameSpecifierLoc QualifierLoc,
+                                          DeclarationNameInfo NameInfo,
+                                          Stmt *Nested) {
+    return getSema().BuildMSDependentExistsStmt(KeywordLoc, IsIfExists,
+                                                QualifierLoc, NameInfo, Nested);
+  }
+
   /// \brief Attach body to a C++0x range-based for statement.
   ///
   /// By default, performs semantic analysis to finish the new statement.
@@ -5747,6 +5760,72 @@ TreeTransform<Derived>::TransformCXXForRangeStmt(CXXForRangeStmt *S) {
 
 template<typename Derived>
 StmtResult
+TreeTransform<Derived>::TransformMSDependentExistsStmt(
+                                                    MSDependentExistsStmt *S) {
+  // Transform the nested-name-specifier, if any.
+  NestedNameSpecifierLoc QualifierLoc;
+  if (S->getQualifierLoc()) {
+    QualifierLoc 
+      = getDerived().TransformNestedNameSpecifierLoc(S->getQualifierLoc());
+    if (!QualifierLoc)
+      return StmtError();
+  }
+
+  // Transform the declaration name.
+  DeclarationNameInfo NameInfo = S->getNameInfo();
+  if (NameInfo.getName()) {
+    NameInfo = getDerived().TransformDeclarationNameInfo(NameInfo);
+    if (!NameInfo.getName())
+      return StmtError();
+  }
+
+  // Check whether anything changed.
+  if (!getDerived().AlwaysRebuild() &&
+      QualifierLoc == S->getQualifierLoc() &&
+      NameInfo.getName() == S->getNameInfo().getName())
+    return S;
+  
+  // Determine whether this name exists, if we can.
+  CXXScopeSpec SS;
+  SS.Adopt(QualifierLoc);
+  bool Dependent = false;
+  switch (getSema().CheckMicrosoftIfExistsSymbol(/*S=*/0, SS, NameInfo)) {
+  case Sema::IER_Exists:
+    if (S->isIfExists())
+      break;
+      
+    return new (getSema().Context) NullStmt(S->getKeywordLoc());
+
+  case Sema::IER_DoesNotExist:
+    if (S->isIfNotExists())
+      break;
+    
+    return new (getSema().Context) NullStmt(S->getKeywordLoc());
+      
+  case Sema::IER_Dependent:
+    Dependent = true;
+    break;
+  }
+  
+  // We need to continue with the instantiation, so do so now.
+  StmtResult SubStmt = getDerived().TransformCompoundStmt(S->getSubStmt());
+  if (SubStmt.isInvalid())
+    return StmtError();
+  
+  // If we have resolved the name, just transform to the substatement.
+  if (!Dependent)
+    return SubStmt;
+  
+  // The name is still dependent, so build a dependent expression again.
+  return getDerived().RebuildMSDependentExistsStmt(S->getKeywordLoc(),
+                                                   S->isIfExists(),
+                                                   QualifierLoc,
+                                                   NameInfo,
+                                                   SubStmt.get());
+}
+
+template<typename Derived>
+StmtResult
 TreeTransform<Derived>::TransformSEHTryStmt(SEHTryStmt *S) {
   StmtResult TryBlock; //  = getDerived().TransformCompoundStmt(S->getTryBlock());
   if(TryBlock.isInvalid()) return StmtError();