From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 15 Jun 2011 14:20:42 +0000 (+0000)
Subject: When performing substitution of default template template parameters
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=383041d31ca14cdf87865ccac6e6f9821d40f61a;p=clang

When performing substitution of default template template parameters
before the template parameters have acquired a proper context (e.g.,
because the enclosing context has yet to be built), provide empty
parameter lists for all outer template parameter scopes to inhibit any
substitution for those template parameters. Fixes PR9643 /
<rdar://problem/9251019>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133055 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 5d4caacd81..d458050585 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2912,16 +2912,6 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
     // arguments, just break out now and we'll fill in the argument pack below.
     if ((*Param)->isTemplateParameterPack())
       break;
-
-    // If our template is a template template parameter that hasn't acquired
-    // its proper context yet (e.g., because we're using the template template
-    // parameter in the signature of a function template, before we've built
-    // the function template itself), don't attempt substitution of default
-    // template arguments at this point: we don't have enough context to
-    // do it properly.
-    if (isTemplateTemplateParameter && 
-        Template->getDeclContext()->isTranslationUnit())
-      break;
     
     // We have a default template argument that we will use.
     TemplateArgumentLoc Arg;
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 3c1964175b..69e592ee25 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -62,8 +62,20 @@ Sema::getTemplateInstantiationArgs(NamedDecl *D,
   if (!Ctx) {
     Ctx = D->getDeclContext();
     
-    assert((!D->isTemplateParameter() || !Ctx->isTranslationUnit()) &&
-           "Template parameter doesn't have its context yet!");
+    // If we have a template template parameter with translation unit context,
+    // then we're performing substitution into a default template argument of
+    // this template template parameter before we've constructed the template
+    // that will own this template template parameter. In this case, we
+    // use empty template parameter lists for all of the outer templates
+    // to avoid performing any substitutions.
+    if (Ctx->isTranslationUnit()) {
+      if (TemplateTemplateParmDecl *TTP 
+                                      = dyn_cast<TemplateTemplateParmDecl>(D)) {
+        for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
+          Result.addOuterTemplateArguments(0, 0);
+        return Result;
+      }
+    }
   }
   
   while (!Ctx->isFileContext()) {
diff --git a/test/SemaTemplate/default-arguments.cpp b/test/SemaTemplate/default-arguments.cpp
index 9ea0fc2e4d..6391369aa5 100644
--- a/test/SemaTemplate/default-arguments.cpp
+++ b/test/SemaTemplate/default-arguments.cpp
@@ -121,3 +121,18 @@ X6<long, X5b> x6c;
 
 
 template<template<class> class X = B<int> > struct X7; // expected-error{{must be a class template}}
+
+namespace PR9643 {
+  template<typename T> class allocator {};
+  template<typename T, typename U = allocator<T> > class vector {};
+
+  template<template<typename U, typename = allocator<U> > class container,
+           typename DT>
+  container<DT> initializer(const DT& d) {
+    return container<DT>();
+  }
+
+  void f() {
+    vector<int, allocator<int> > v = initializer<vector>(5);
+  }
+}