PR13243: When deducing a non-type template parameter which is specified as an

expression, skip over any SubstNonTypeTemplateParmExprs which alias templates
may have inserted before checking for a DeclRefExpr referring to a non-type
template parameter declaration.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159909 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 20 insertions, 2 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 310d9b36cb..b8ec59ee1d 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -137,8 +137,17 @@ DeduceTemplateArguments(Sema &S,
 /// of a non-type template parameter, return the declaration of that
 /// non-type template parameter.
 static NonTypeTemplateParmDecl *getDeducedParameterFromExpr(Expr *E) {
-  if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
-    E = IC->getSubExpr();
+  // If we are within an alias template, the expression may have undergone
+  // any number of parameter substitutions already.
+  while (1) {
+    if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
+      E = IC->getSubExpr();
+    else if (SubstNonTypeTemplateParmExpr *Subst =
+               dyn_cast<SubstNonTypeTemplateParmExpr>(E))
+      E = Subst->getReplacement();
+    else
+      break;
+  }
 
   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
     return dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
diff --git a/test/SemaTemplate/alias-templates.cpp b/test/SemaTemplate/alias-templates.cpp
index 75615ee295..a074bc4e1e 100644
--- a/test/SemaTemplate/alias-templates.cpp
+++ b/test/SemaTemplate/alias-templates.cpp
@@ -100,3 +100,12 @@ namespace PR11848 {
   Hidden1<Hide> h1;  // expected-note{{in instantiation of template class 'PR11848::Hidden1<PR11848::Hide>' requested here}}
   Hidden2<Hide, double, char> h2(1, 2);
 }
+
+namespace PR13243 {
+  template<typename A> struct X {};
+  template<int I> struct C {};
+  template<int I> using Ci = C<I>;
+
+  template<typename A, int I> void f(X<A>, Ci<I>) {}
+  template void f(X<int>, C<0>);
+}