From 64cf3efd47bc79b661c93cea5a7a3fa60bba16d8 Mon Sep 17 00:00:00 2001
From: Larisse Voufo <lvoufo@google.com>
Date: Thu, 27 Jun 2013 01:50:25 +0000
Subject: [PATCH] Fix a conversion to incomplete type bug -- The error message
 now specifically states that the type is incomplete and points to the forward
 declaration of the incomplete type.

llvm-svn: 185056
---
 .../clang/Basic/DiagnosticSemaKinds.td        |  2 ++
 clang/lib/Sema/SemaInit.cpp                   | 12 +++++++---
 clang/lib/Sema/SemaOverload.cpp               | 13 +++++++----
 .../SemaCXX/conversion-incomplete-type.cpp    | 23 +++++++++++++++++++
 4 files changed, 43 insertions(+), 7 deletions(-)
 create mode 100644 clang/test/SemaCXX/conversion-incomplete-type.cpp

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 5428550e85fd..54157b317abe 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5014,6 +5014,8 @@ def err_typecheck_ambiguous_condition : Error<
   "conversion %diff{from $ to $|between types}0,1 is ambiguous">;
 def err_typecheck_nonviable_condition : Error<
   "no viable conversion%diff{ from $ to $|}0,1">;
+def err_typecheck_nonviable_condition_incomplete : Error<
+  "no viable conversion%diff{ from $ to incomplete type $|}0,1">;
 def err_typecheck_deleted_function : Error<
   "conversion function %diff{from $ to $|between types}0,1 "
   "invokes a deleted function">;
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 9d7fcda8fddd..cbca84da9257 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -6251,9 +6251,15 @@ bool InitializationSequence::Diagnose(Sema &S,
       break;
 
     case OR_No_Viable_Function:
-      S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
-        << Args[0]->getType() << DestType.getNonReferenceType()
-        << Args[0]->getSourceRange();
+      if (!DestType.getNonReferenceType()->isIncompleteType() ||
+          !S.RequireCompleteType(Kind.getLocation(),
+                                 DestType.getNonReferenceType(),
+                          diag::err_typecheck_nonviable_condition_incomplete,
+                               Args[0]->getType(), Args[0]->getSourceRange()))
+        S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
+          << Args[0]->getType() << Args[0]->getSourceRange()
+          << DestType.getNonReferenceType();
+
       FailedCandidateSet.NoteCandidates(S, OCD_AllCandidates, Args);
       break;
 
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index d4d08b4bff8d..b1fe76a8f61a 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -3231,10 +3231,15 @@ Sema::DiagnoseMultipleUserDefinedConversion(Expr *From, QualType ToType) {
     Diag(From->getLocStart(),
          diag::err_typecheck_ambiguous_condition)
           << From->getType() << ToType << From->getSourceRange();
-  else if (OvResult == OR_No_Viable_Function && !CandidateSet.empty())
-    Diag(From->getLocStart(),
-         diag::err_typecheck_nonviable_condition)
-    << From->getType() << ToType << From->getSourceRange();
+  else if (OvResult == OR_No_Viable_Function && !CandidateSet.empty()) {
+    if (!ToType->isIncompleteType() ||
+        !RequireCompleteType(From->getLocStart(), ToType,
+                          diag::err_typecheck_nonviable_condition_incomplete,
+                             From->getType(), From->getSourceRange()))
+      Diag(From->getLocStart(),
+           diag::err_typecheck_nonviable_condition)
+           << From->getType() << From->getSourceRange() << ToType;
+  }
   else
     return false;
   CandidateSet.NoteCandidates(*this, OCD_AllCandidates, From);
diff --git a/clang/test/SemaCXX/conversion-incomplete-type.cpp b/clang/test/SemaCXX/conversion-incomplete-type.cpp
new file mode 100644
index 000000000000..ebedd04047b9
--- /dev/null
+++ b/clang/test/SemaCXX/conversion-incomplete-type.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct string {};
+
+class StringPiece;  // expected-note {{forward declaration of 'StringPiece'}} \
+                    // expected-note {{forward declaration of 'StringPiece'}}
+
+struct Test {
+  void expectStringPiece(const StringPiece& blah) {};  // expected-note {{passing argument to parameter 'blah' here}}
+  
+  void test(const string& s) { 
+    expectStringPiece(s);  // expected-error {{no viable conversion from 'const string' to incomplete type 'const StringPiece'}}
+  }
+};
+
+struct TestStatic {
+  static void expectStringPiece(const StringPiece& blah) {};  // expected-note {{passing argument to parameter 'blah' here}}
+  
+  static void test(const string& s) { 
+    expectStringPiece(s);  // expected-error {{no viable conversion from 'const string' to incomplete type 'const StringPiece'}}
+  }
+};
+