1 files changed, 61 insertions, 50 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index adcf2ee00e7..fe1775e1eb5 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11045,6 +11045,11 @@ Sema::FinalizeDeclaration(Decl *ThisDecl) {
   }
 }
 
+static bool hasDeducedAuto(DeclaratorDecl *DD) {
+  auto *VD = dyn_cast<VarDecl>(DD);
+  return VD && !VD->getType()->hasAutoForTrailingReturnType();
+}
+
 Sema::DeclGroupPtrTy Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
                                                    ArrayRef<Decl *> Group) {
   SmallVector<Decl*, 8> Decls;
@@ -11055,29 +11060,46 @@ Sema::DeclGroupPtrTy Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
   DeclaratorDecl *FirstDeclaratorInGroup = nullptr;
   DecompositionDecl *FirstDecompDeclaratorInGroup = nullptr;
   bool DiagnosedMultipleDecomps = false;
+  DeclaratorDecl *FirstNonDeducedAutoInGroup = nullptr;
+  bool DiagnosedNonDeducedAuto = false;
 
   for (unsigned i = 0, e = Group.size(); i != e; ++i) {
     if (Decl *D = Group[i]) {
-      auto *DD = dyn_cast<DeclaratorDecl>(D);
-      if (DD && !FirstDeclaratorInGroup)
-        FirstDeclaratorInGroup = DD;
-
-      auto *Decomp = dyn_cast<DecompositionDecl>(D);
-      if (Decomp && !FirstDecompDeclaratorInGroup)
-        FirstDecompDeclaratorInGroup = Decomp;
-
-      // A decomposition declaration cannot be combined with any other
-      // declaration in the same group.
-      auto *OtherDD = FirstDeclaratorInGroup;
-      if (OtherDD == FirstDecompDeclaratorInGroup)
-        OtherDD = DD;
-      if (OtherDD && FirstDecompDeclaratorInGroup &&
-          OtherDD != FirstDecompDeclaratorInGroup &&
-          !DiagnosedMultipleDecomps) {
-        Diag(FirstDecompDeclaratorInGroup->getLocation(),
-             diag::err_decomp_decl_not_alone)
-          << OtherDD->getSourceRange();
-        DiagnosedMultipleDecomps = true;
+      // For declarators, there are some additional syntactic-ish checks we need
+      // to perform.
+      if (auto *DD = dyn_cast<DeclaratorDecl>(D)) {
+        if (!FirstDeclaratorInGroup)
+          FirstDeclaratorInGroup = DD;
+        if (!FirstDecompDeclaratorInGroup)
+          FirstDecompDeclaratorInGroup = dyn_cast<DecompositionDecl>(D);
+        if (!FirstNonDeducedAutoInGroup && DS.containsPlaceholderType() &&
+            !hasDeducedAuto(DD))
+          FirstNonDeducedAutoInGroup = DD;
+
+        if (FirstDeclaratorInGroup != DD) {
+          // A decomposition declaration cannot be combined with any other
+          // declaration in the same group.
+          if (FirstDecompDeclaratorInGroup && !DiagnosedMultipleDecomps) {
+            Diag(FirstDecompDeclaratorInGroup->getLocation(),
+                 diag::err_decomp_decl_not_alone)
+                << FirstDeclaratorInGroup->getSourceRange()
+                << DD->getSourceRange();
+            DiagnosedMultipleDecomps = true;
+          }
+
+          // A declarator that uses 'auto' in any way other than to declare a
+          // variable with a deduced type cannot be combined with any other
+          // declarator in the same group.
+          if (FirstNonDeducedAutoInGroup && !DiagnosedNonDeducedAuto) {
+            Diag(FirstNonDeducedAutoInGroup->getLocation(),
+                 diag::err_auto_non_deduced_not_alone)
+                << FirstNonDeducedAutoInGroup->getType()
+                       ->hasAutoForTrailingReturnType()
+                << FirstDeclaratorInGroup->getSourceRange()
+                << DD->getSourceRange();
+            DiagnosedNonDeducedAuto = true;
+          }
+        }
       }
 
       Decls.push_back(D);
@@ -11105,38 +11127,27 @@ Sema::BuildDeclaratorGroup(MutableArrayRef<Decl *> Group) {
   //   deduction, the program is ill-formed.
   if (Group.size() > 1) {
     QualType Deduced;
-    CanQualType DeducedCanon;
     VarDecl *DeducedDecl = nullptr;
     for (unsigned i = 0, e = Group.size(); i != e; ++i) {
-      if (VarDecl *D = dyn_cast<VarDecl>(Group[i])) {
-        AutoType *AT = D->getType()->getContainedAutoType();
-        // FIXME: DR1265: if we have a function pointer declaration, we can have
-        // an 'auto' from a trailing return type. In that case, the return type
-        // must match the various other uses of 'auto'.
-        if (!AT)
-          continue;
-        // Don't reissue diagnostics when instantiating a template.
-        if (D->isInvalidDecl())
-          break;
-        QualType U = AT->getDeducedType();
-        if (!U.isNull()) {
-          CanQualType UCanon = Context.getCanonicalType(U);
-          if (Deduced.isNull()) {
-            Deduced = U;
-            DeducedCanon = UCanon;
-            DeducedDecl = D;
-          } else if (DeducedCanon != UCanon) {
-            Diag(D->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
-                 diag::err_auto_different_deductions)
-              << (unsigned)AT->getKeyword()
-              << Deduced << DeducedDecl->getDeclName()
-              << U << D->getDeclName()
-              << DeducedDecl->getInit()->getSourceRange()
-              << D->getInit()->getSourceRange();
-            D->setInvalidDecl();
-            break;
-          }
-        }
+      VarDecl *D = dyn_cast<VarDecl>(Group[i]);
+      if (!D || D->isInvalidDecl())
+        break;
+      AutoType *AT = D->getType()->getContainedAutoType();
+      if (!AT || AT->getDeducedType().isNull())
+        continue;
+      if (Deduced.isNull()) {
+        Deduced = AT->getDeducedType();
+        DeducedDecl = D;
+      } else if (!Context.hasSameType(AT->getDeducedType(), Deduced)) {
+        Diag(D->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
+             diag::err_auto_different_deductions)
+          << (unsigned)AT->getKeyword()
+          << Deduced << DeducedDecl->getDeclName()
+          << AT->getDeducedType() << D->getDeclName()
+          << DeducedDecl->getInit()->getSourceRange()
+          << D->getInit()->getSourceRange();
+        D->setInvalidDecl();
+        break;
       }
     }
   }