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

2 files changed, 14 insertions, 12 deletions

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()) {