r247486 - [modules] When picking one of two template declarations as a lookup result,

[Richard Smith via cfe-commits]

Author: rsmith
Date: Fri Sep 11 17:39:35 2015
New Revision: 247486

URL: http://llvm.org/viewvc/llvm-project?rev=247486&view=rev
Log:
[modules] When picking one of two template declarations as a lookup result,
it's not sufficient to prefer the declaration with more default arguments, or
the one that's visible; they might both be visible, but one of them might have
a visible default argument where the other has a hidden default argument.

Modified:
    cfe/trunk/lib/Sema/SemaLookup.cpp
    cfe/trunk/test/Modules/Inputs/template-default-args/a.h
    cfe/trunk/test/Modules/Inputs/template-default-args/module.modulemap
    cfe/trunk/test/Modules/template-default-args.cpp

Modified: cfe/trunk/lib/Sema/SemaLookup.cpp
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaLookup.cpp?rev=247486&r1=247485&r2=247486&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaLookup.cpp (original)
+++ cfe/trunk/lib/Sema/SemaLookup.cpp Fri Sep 11 17:39:35 2015
@@ -387,6 +387,8 @@ static bool isPreferredLookupResult(Sema
     // If D has more default arguments, it is preferred.
     if (DMin != EMin)
       return DMin < EMin;
+    // FIXME: When we track visibility for default function arguments, check
+    // that we pick the declaration with more visible default arguments.
   }
 
   // Pick the template with more default template arguments.
@@ -394,9 +396,22 @@ static bool isPreferredLookupResult(Sema
     auto *ETD = cast<TemplateDecl>(EUnderlying);
     unsigned DMin = DTD->getTemplateParameters()->getMinRequiredArguments();
     unsigned EMin = ETD->getTemplateParameters()->getMinRequiredArguments();
-    // If D has more default arguments, it is preferred.
+    // If D has more default arguments, it is preferred. Note that default
+    // arguments (and their visibility) is monotonically increasing across the
+    // redeclaration chain, so this is a quick proxy for "is more recent".
     if (DMin != EMin)
       return DMin < EMin;
+    // If D has more *visible* default arguments, it is preferred. Note, an
+    // earlier default argument being visible does not imply that a later
+    // default argument is visible, so we can't just check the first one.
+    for (unsigned I = DMin, N = DTD->getTemplateParameters()->size();
+        I != N; ++I) {
+      if (!S.hasVisibleDefaultArgument(
+              ETD->getTemplateParameters()->getParam(I)) &&
+          S.hasVisibleDefaultArgument(
+              DTD->getTemplateParameters()->getParam(I)))
+        return true;
+    }
   }
 
   // For most kinds of declaration, it doesn't really matter which one we pick.

Modified: cfe/trunk/test/Modules/Inputs/template-default-args/a.h
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/template-default-args/a.h?rev=247486&r1=247485&r2=247486&view=diff
==============================================================================
--- cfe/trunk/test/Modules/Inputs/template-default-args/a.h (original)
+++ cfe/trunk/test/Modules/Inputs/template-default-args/a.h Fri Sep 11 17:39:35 
2015
@@ -9,4 +9,8 @@ template<typename T = int> struct H;
 template<typename T> struct J {};
 template<typename T = int> struct J;
 struct K : J<> {};
+template<typename T = void> struct L;
+struct FriendL {
+  template<typename T> friend struct L;
+};
 END

Modified: cfe/trunk/test/Modules/Inputs/template-default-args/module.modulemap
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/Inputs/template-default-args/module.modulemap?rev=247486&r1=247485&r2=247486&view=diff
==============================================================================
--- cfe/trunk/test/Modules/Inputs/template-default-args/module.modulemap 
(original)
+++ cfe/trunk/test/Modules/Inputs/template-default-args/module.modulemap Fri 
Sep 11 17:39:35 2015
@@ -3,3 +3,6 @@ module X {
   module B { header "b.h" }
   module C { header "c.h" }
 }
+module Y {
+  module D { header "d.h" }
+}

Modified: cfe/trunk/test/Modules/template-default-args.cpp
URL: 
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/template-default-args.cpp?rev=247486&r1=247485&r2=247486&view=diff
==============================================================================
--- cfe/trunk/test/Modules/template-default-args.cpp (original)
+++ cfe/trunk/test/Modules/template-default-args.cpp Fri Sep 11 17:39:35 2015
@@ -13,6 +13,7 @@ template<typename T = int, typename U =
 END
 
 #include "b.h"
+#include "d.h"
 
 BEGIN
 template<typename T = int> struct A {};
@@ -41,4 +42,5 @@ G<> g; // expected-error {{default argum
 H<> h; // expected-error {{default argument of 'H' must be imported from 
module 'X.A' before it is required}}
 // expected-note@a.h:8 {{default argument declared here}}
 I<> i;
+L<> *l;
 END


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