From 700204189d7171b725f95238c7dda55e12840ab3 Mon Sep 17 00:00:00 2001
From: David Blaikie <dblaikie@gmail.com>
Date: Fri, 4 Mar 2016 22:29:11 +0000
Subject: [PATCH] PR5941 - improve diagnostic for * vs & confusion when
 choosing overload candidate with a parameter of incomplete (ref or pointer)
 type

Reviewers: dblaikie

Differential Revision: http://reviews.llvm.org/D16949

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@262752 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td |  7 ++++++-
 lib/Sema/SemaOverload.cpp                  |  5 ++++-
 test/SemaCXX/overload-call.cpp             | 24 ++++++++++++++--------
 3 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index a3a60fb270..c5faa6eb74 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3219,7 +3219,12 @@ def note_ovl_candidate_bad_conv_incomplete : Note<"candidate "
     "function (the implicit move assignment operator)|"
     "constructor (inherited)}0%1 "
     "not viable: cannot convert argument of incomplete type "
-    "%diff{$ to $|to parameter type}2,3">;
+    "%diff{$ to $|to parameter type}2,3 for "
+    "%select{%ordinal5 argument|object argument}4"
+    "%select{|; dereference the argument with *|"
+    "; take the address of the argument with &|"
+    "; remove *|"
+    "; remove &}6">;
 def note_ovl_candidate_bad_list_argument : Note<"candidate "
     "%select{function|function|constructor|"
     "function |function |constructor |"
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 2ad49933d4..1765db6734 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -9131,10 +9131,13 @@ static void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand,
   if (const PointerType *PTy = TempFromTy->getAs<PointerType>())
     TempFromTy = PTy->getPointeeType();
   if (TempFromTy->isIncompleteType()) {
+    // Emit the generic diagnostic and, optionally, add the hints to it.
     S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_conv_incomplete)
       << (unsigned) FnKind << FnDesc
       << (FromExpr ? FromExpr->getSourceRange() : SourceRange())
-      << FromTy << ToTy << (unsigned) isObjectArgument << I+1;
+      << FromTy << ToTy << (unsigned) isObjectArgument << I+1
+      << (unsigned) (Cand->Fix.Kind);
+      
     MaybeEmitInheritedConstructorNote(S, Fn);
     return;
   }
diff --git a/test/SemaCXX/overload-call.cpp b/test/SemaCXX/overload-call.cpp
index 3d286a94a0..7eaf98b601 100644
--- a/test/SemaCXX/overload-call.cpp
+++ b/test/SemaCXX/overload-call.cpp
@@ -375,16 +375,24 @@ namespace test2 {
 }
 
 // PR 6117
-namespace test3 {
-  struct Base {};
+namespace IncompleteConversion {
+  struct Complete {};
   struct Incomplete;
 
-  void foo(Base *); // expected-note 2 {{cannot convert argument of incomplete type}}
-  void foo(Base &); // expected-note 2 {{cannot convert argument of incomplete type}}
-
-  void test(Incomplete *P) {
-    foo(P); // expected-error {{no matching function for call to 'foo'}}
-    foo(*P); // expected-error {{no matching function for call to 'foo'}}
+  void completeFunction(Complete *); // expected-note 2 {{cannot convert argument of incomplete type}}
+  void completeFunction(Complete &); // expected-note 2 {{cannot convert argument of incomplete type}}
+  
+  void testTypeConversion(Incomplete *P) {
+    completeFunction(P); // expected-error {{no matching function for call to 'completeFunction'}}
+    completeFunction(*P); // expected-error {{no matching function for call to 'completeFunction'}}
+  }
+  
+  void incompletePointerFunction(Incomplete *); // expected-note {{candidate function not viable: cannot convert argument of incomplete type 'IncompleteConversion::Incomplete' to 'IncompleteConversion::Incomplete *' for 1st argument; take the address of the argument with &}}
+  void incompleteReferenceFunction(Incomplete &); // expected-note {{candidate function not viable: cannot convert argument of incomplete type 'IncompleteConversion::Incomplete *' to 'IncompleteConversion::Incomplete &' for 1st argument; dereference the argument with *}}
+  
+  void testPointerReferenceConversion(Incomplete &reference, Incomplete *pointer) {
+    incompletePointerFunction(reference); // expected-error {{no matching function for call to 'incompletePointerFunction'}}
+    incompleteReferenceFunction(pointer); // expected-error {{no matching function for call to 'incompleteReferenceFunction'}}
   }
 }
 
-- 
2.40.0