commit 7ad0b88396522d4abf3973cd95d2f28f40af7b54
author Richard Smith <richard-llvm@metafoo.co.uk> Wed Apr 02 21:44:35 2014 +0000
committer Richard Smith <richard-llvm@metafoo.co.uk> Wed Apr 02 21:44:35 2014 +0000
tree 1e7381f3b8cbb12e199bd151db65d32c2078e89d
parent d33a3d8892936d4736addf1968f6da76d19e4e1e

If a using-declaration names a class member, but appears outside a class, try
to suggest a different syntax to get the same effect.

llvm-svn: 205467

clang/lib/Sema/SemaDeclCXX.cpp

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index dac2490..850db26 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -7393,7 +7393,7 @@
     return 0;
 
   // Check for bad qualifiers.
-  if (CheckUsingDeclQualifier(UsingLoc, SS, IdentLoc))
+  if (CheckUsingDeclQualifier(UsingLoc, SS, NameInfo, IdentLoc))
     return 0;
 
   DeclContext *LookupContext = computeDeclContext(SS);
@@ -7619,6 +7619,7 @@
 /// scope.  If an error is found, diagnoses it and returns true.
 bool Sema::CheckUsingDeclQualifier(SourceLocation UsingLoc,
                                    const CXXScopeSpec &SS,
+                                   const DeclarationNameInfo &NameInfo,
                                    SourceLocation NameLoc) {
   DeclContext *NamedContext = computeDeclContext(SS);
 
@@ -7630,8 +7631,56 @@
     // If we weren't able to compute a valid scope, it must be a
     // dependent class scope.
     if (!NamedContext || NamedContext->isRecord()) {
+      auto *RD = dyn_cast<CXXRecordDecl>(NamedContext);
+      if (RD && RequireCompleteDeclContext(const_cast<CXXScopeSpec&>(SS), RD))
+        RD = 0;
+
       Diag(NameLoc, diag::err_using_decl_can_not_refer_to_class_member)
         << SS.getRange();
+
+      // If we have a complete, non-dependent source type, try to suggest a
+      // way to get the same effect.
+      if (!RD)
+        return true;
+
+      // Find what this using-declaration was referring to.
+      LookupResult R(*this, NameInfo, LookupOrdinaryName);
+      R.setHideTags(false);
+      R.suppressDiagnostics();
+      LookupQualifiedName(R, RD);
+
+      if (R.getAsSingle<TypeDecl>()) {
+        if (getLangOpts().CPlusPlus11) {
+          // Convert 'using X::Y;' to 'using Y = X::Y;'.
+          Diag(SS.getBeginLoc(), diag::note_using_decl_class_member_workaround)
+            << 0 // alias declaration
+            << FixItHint::CreateInsertion(SS.getBeginLoc(),
+                                          NameInfo.getName().getAsString() +
+                                              " = ");
+        } else {
+          // Convert 'using X::Y;' to 'typedef X::Y Y;'.
+          SourceLocation InsertLoc =
+              PP.getLocForEndOfToken(NameInfo.getLocEnd());
+          Diag(InsertLoc, diag::note_using_decl_class_member_workaround)
+            << 1 // typedef declaration
+            << FixItHint::CreateReplacement(UsingLoc, "typedef")
+            << FixItHint::CreateInsertion(
+                   InsertLoc, " " + NameInfo.getName().getAsString());
+        }
+      } else if (R.getAsSingle<VarDecl>()) {
+        // Don't provide a fixit outside C++11 mode; we don't want to suggest
+        // repeating the type of the static data member here.
+        FixItHint FixIt;
+        if (getLangOpts().CPlusPlus11) {
+          // Convert 'using X::Y;' to 'auto &Y = X::Y;'.
+          FixIt = FixItHint::CreateReplacement(
+              UsingLoc, "auto &" + NameInfo.getName().getAsString() + " = ");
+        }
+
+        Diag(UsingLoc, diag::note_using_decl_class_member_workaround)
+          << 2 // reference declaration
+          << FixIt;
+      }
       return true;
     }