From 838925dc841f0968ac5daf941aed5d2331775a59 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 13 Jul 2012 04:12:04 +0000
Subject: [PATCH] Provide a special-case diagnostic when two class member
 functions instantiate to the same signature. Fix a bug in the type printer
 which would cause this diagnostic to print wonderful types like 'const const
 int *'.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160161 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td |  2 ++
 lib/AST/TypePrinter.cpp                    | 14 ++++++++---
 lib/Sema/SemaDecl.cpp                      | 27 +++++++++++++---------
 test/SemaTemplate/instantiate-method.cpp   |  9 +++++++-
 4 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 769285a0b8..b08b342819 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3799,6 +3799,8 @@ def note_enum_specialized_here : Note<
   "enum %0 was explicitly specialized here">;
 
 def err_member_redeclared : Error<"class member cannot be redeclared">;
+def err_member_redeclared_in_instantiation : Error<
+  "multiple overloads of %0 instantiate to the same signature %1">;
 def err_member_name_of_class : Error<"member %0 has the same name as its class">;
 def err_member_def_undefined_record : Error<
   "out-of-line definition of %0 from class %1 without definition">;
diff --git a/lib/AST/TypePrinter.cpp b/lib/AST/TypePrinter.cpp
index 7567a73311..c42117c82b 100644
--- a/lib/AST/TypePrinter.cpp
+++ b/lib/AST/TypePrinter.cpp
@@ -226,9 +226,17 @@ bool TypePrinter::canPrefixQualifiers(const Type *T,
   return CanPrefixQualifiers;
 }
 
-void TypePrinter::printBefore(QualType t, raw_ostream &OS) {
-  SplitQualType split = t.split();
-  printBefore(split.Ty, split.Quals, OS);
+void TypePrinter::printBefore(QualType T, raw_ostream &OS) {
+  SplitQualType Split = T.split();
+
+  // If we have cv1 T, where T is substituted for cv2 U, only print cv1 - cv2
+  // at this level.
+  Qualifiers Quals = Split.Quals;
+  if (const SubstTemplateTypeParmType *Subst =
+        dyn_cast<SubstTemplateTypeParmType>(Split.Ty))
+    Quals -= QualType(Subst, 0).getQualifiers();
+
+  printBefore(Split.Ty, Quals, OS);
 }
 
 /// \brief Prints the part of the type string before an identifier, e.g. for
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index f00ed8279b..cbf2368f71 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2063,22 +2063,27 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, Decl *OldD, Scope *S) {
           Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();
           return true;
         }
-      
+
         // C++ [class.mem]p1:
         //   [...] A member shall not be declared twice in the
         //   member-specification, except that a nested class or member
         //   class template can be declared and then later defined.
-        unsigned NewDiag;
-        if (isa<CXXConstructorDecl>(OldMethod))
-          NewDiag = diag::err_constructor_redeclared;
-        else if (isa<CXXDestructorDecl>(NewMethod))
-          NewDiag = diag::err_destructor_redeclared;
-        else if (isa<CXXConversionDecl>(NewMethod))
-          NewDiag = diag::err_conv_function_redeclared;
-        else
-          NewDiag = diag::err_member_redeclared;
+        if (ActiveTemplateInstantiations.empty()) {
+          unsigned NewDiag;
+          if (isa<CXXConstructorDecl>(OldMethod))
+            NewDiag = diag::err_constructor_redeclared;
+          else if (isa<CXXDestructorDecl>(NewMethod))
+            NewDiag = diag::err_destructor_redeclared;
+          else if (isa<CXXConversionDecl>(NewMethod))
+            NewDiag = diag::err_conv_function_redeclared;
+          else
+            NewDiag = diag::err_member_redeclared;
 
-        Diag(New->getLocation(), NewDiag);
+          Diag(New->getLocation(), NewDiag);
+        } else {
+          Diag(New->getLocation(), diag::err_member_redeclared_in_instantiation)
+            << New << New->getType();
+        }
         Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();
 
       // Complain if this is an explicit declaration of a special
diff --git a/test/SemaTemplate/instantiate-method.cpp b/test/SemaTemplate/instantiate-method.cpp
index 363115d184..5e9da3f688 100644
--- a/test/SemaTemplate/instantiate-method.cpp
+++ b/test/SemaTemplate/instantiate-method.cpp
@@ -173,5 +173,12 @@ namespace PR7022 {
     typedef X2<> X2_type;
     X2_type c;
   }
-
+}
+
+namespace SameSignatureAfterInstantiation {
+  template<typename T> struct S {
+    void f(T *); // expected-note {{previous}}
+    void f(const T*); // expected-error {{multiple overloads of 'f' instantiate to the same signature 'void (const int *)'}}
+  };
+  S<const int> s; // expected-note {{instantiation}}
 }