commit 4576a77b809649f5b8d0ff8c7a4be57eeee0ecf9
author Richard Smith <richard-llvm@metafoo.co.uk> Mon Sep 10 06:35:32 2018 +0000
committer Richard Smith <richard-llvm@metafoo.co.uk> Mon Sep 10 06:35:32 2018 +0000
tree 26b3a2987ae7f0dfcbf7e3c0d0e34ac246a547cb
parent 4d10ba37b93755fa7a843e24b92f9bfc5b1b805d

PR33222: Require the declared return type not the actual return type to
match when checking for redeclaration of a function template.

This properly handles differences in deduced return types, particularly
when performing redeclaration checks for a friend function template.

llvm-svn: 341778

clang/lib/Sema/SemaDecl.cpp

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 5389787..496d06c 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3245,20 +3245,15 @@
     //   Redeclarations or specializations of a function or function template
     //   with a declared return type that uses a placeholder type shall also
     //   use that placeholder, not a deduced type.
-    QualType OldDeclaredReturnType =
-        (Old->getTypeSourceInfo()
-             ? Old->getTypeSourceInfo()->getType()->castAs<FunctionType>()
-             : OldType)->getReturnType();
-    QualType NewDeclaredReturnType =
-        (New->getTypeSourceInfo()
-             ? New->getTypeSourceInfo()->getType()->castAs<FunctionType>()
-             : NewType)->getReturnType();
+    QualType OldDeclaredReturnType = Old->getDeclaredReturnType();
+    QualType NewDeclaredReturnType = New->getDeclaredReturnType();
     if (!Context.hasSameType(OldDeclaredReturnType, NewDeclaredReturnType) &&
         canFullyTypeCheckRedeclaration(New, Old, NewDeclaredReturnType,
                                        OldDeclaredReturnType)) {
       QualType ResQT;
       if (NewDeclaredReturnType->isObjCObjectPointerType() &&
           OldDeclaredReturnType->isObjCObjectPointerType())
+        // FIXME: This does the wrong thing for a deduced return type.
         ResQT = Context.mergeObjCGCQualifiers(NewQType, OldQType);
       if (ResQT.isNull()) {
         if (New->isCXXClassMember() && New->isOutOfLine())

clang/lib/Sema/SemaOverload.cpp

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index cb80a69..35636e7 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1105,7 +1105,8 @@
       (!TemplateParameterListsAreEqual(NewTemplate->getTemplateParameters(),
                                        OldTemplate->getTemplateParameters(),
                                        false, TPL_TemplateMatch) ||
-       OldType->getReturnType() != NewType->getReturnType()))
+       !Context.hasSameType(Old->getDeclaredReturnType(),
+                            New->getDeclaredReturnType())))
     return true;
 
   // If the function is a class member, its signature includes the

clang/lib/Sema/SemaTemplate.cpp

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 45ce118..c826b83 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -8294,6 +8294,8 @@
         QualType Adjusted = Function->getType();
         if (!hasExplicitCallingConv(Adjusted))
           Adjusted = adjustCCAndNoReturn(Adjusted, Method->getType());
+        // This doesn't handle deduced return types, but both function
+        // declarations should be undeduced at this point.
         if (Context.hasSameType(Adjusted, Method->getType())) {
           FoundInstantiation = *I;
           Instantiation = Method;