C++ PATCH for c++/85060, wrong-code calling base member from template

[Jason Merrill]

Here, during instantiate_non_dependent_expr, we were getting the wrong
answer for any_dependent_bases_p because processing_template_decl was
temporarily cleared.  Fixed by using uses_template_parms (which
doesn't depend on processing_template_decl) on the type we're asking
about.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit 4c894923eba7d2a86836e43cc1093247a3241a7e
Author: Jason Merrill <ja...@redhat.com>
Date:   Fri Mar 23 11:14:50 2018 -0400

            PR c++/85060 - wrong-code with call to base member in template.
    
            * search.c (any_dependent_bases_p): Check uses_template_parms
            rather than processing_template_decl.

diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index 6bf8b0e70dc..bfeaf2cc819 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -2619,7 +2619,7 @@ original_binfo (tree binfo, tree here)
 bool
 any_dependent_bases_p (tree type)
 {
-  if (!type || !CLASS_TYPE_P (type) || !processing_template_decl)
+  if (!type || !CLASS_TYPE_P (type) || !uses_template_parms (type))
     return false;
 
   /* If we haven't set TYPE_BINFO yet, we don't know anything about the bases.
diff --git a/gcc/testsuite/g++.dg/template/dependent-base3.C b/gcc/testsuite/g++.dg/template/dependent-base3.C
new file mode 100644
index 00000000000..e38b968e774
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/dependent-base3.C
@@ -0,0 +1,26 @@
+// PR c++/85060
+// { dg-do compile { target c++14 } }
+
+struct CA {
+  constexpr int foo() const { return 42; }
+};
+
+template <class T>
+struct CB : CA { };
+
+template <class T>
+struct CC : CB<T> {
+  constexpr int bar() const {
+    const int m = CA::foo();
+    return m;
+  }
+
+  constexpr int baz() const {
+    const T m = CA::foo();
+    return m;
+  }
+};
+
+constexpr CC<double> c;
+
+static_assert( c.bar() == 42, "" );