PR c++/90047 - ICE with enable_if alias template.

In order to make alias templates useful for SFINAE we instantiate them under
the prevailing 'complain' argument, so an error encountered while
instantiating during SFINAE context is silent.  The problem in this PR comes
when we later look up the erroneous instantiation and don't give an error at
that point.  Fixed by not adding an erroneous instantiation to the hash
table, so we instantiate it again when needed and get the error.  This
required changes to a number of tests, which previously said "substitution
failed:" with no explanation of what the failure was; now we properly
explain.

	* pt.c (tsubst_decl) [TYPE_DECL]: Don't put an erroneous decl in the
	hash table when we're in SFINAE context.

From-SVN: r270433

4 files changed, 40 insertions, 1 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a37a6c2..bfaf355 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-04-17  Jason Merrill  <jason@redhat.com>
+
+	PR c++/90047 - ICE with enable_if alias template.
+	* pt.c (tsubst_decl) [TYPE_DECL]: Don't put an erroneous decl in the
+	hash table when we're in SFINAE context.
+
 2019-04-17  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/90124 - bogus error with incomplete type in decltype.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f800131..3a11eaa 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13948,7 +13948,8 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
 
 	    DECL_TEMPLATE_INFO (r) = build_template_info (tmpl, argvec);
 	    SET_DECL_IMPLICIT_INSTANTIATION (r);
-	    register_specialization (r, gen_tmpl, argvec, false, hash);
+	    if (!error_operand_p (r) || (complain & tf_error))
+	      register_specialization (r, gen_tmpl, argvec, false, hash);
 	  }
 	else
 	  {
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-67.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-67.C
new file mode 100644
index 0000000..55961cc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-67.C
@@ -0,0 +1,30 @@
+// PR c++/90047
+// { dg-do compile { target c++11 } }
+
+template <int a> struct b { static constexpr int c = a; };
+template <typename> struct aa;
+template <typename...> struct d;
+template <typename e, typename f, typename g, typename... h>
+struct d<e, f, g, h...> : aa<e>::i {};
+template <typename> struct j;
+template <typename k, long l> struct j<k[l]> : b<true> {};
+struct m {
+  typedef b<0> i;
+};
+template <typename> struct n : m::i {};
+template <bool> struct o;
+template <typename p> struct aa { typedef p i; };
+template <bool ab> using ac = typename o<ab>::i; // { dg-error "incomplete" }
+class q {
+  template <typename k, typename> using ad = ac<d<n<k>, int, int>::c>;
+  template <typename k, typename = ad<k, void>> q(k &);
+};
+template <typename r> struct s {
+  s(r) { t; }
+  template <ac<!j<r>::c> *> void t();
+};
+class I {
+  friend char operator<<(char p1, I p2) { return p1 << p2; }
+  q ag;
+};
+int main() { s<char[10]> a = (char *)""; }
diff --git a/gcc/testsuite/g++.old-deja/g++.robertl/eb43.C b/gcc/testsuite/g++.old-deja/g++.robertl/eb43.C
index 1dc4328..90afbe4 100644
--- a/gcc/testsuite/g++.old-deja/g++.robertl/eb43.C
+++ b/gcc/testsuite/g++.old-deja/g++.robertl/eb43.C
@@ -42,3 +42,5 @@ int main()
   sort( a.begin(), a.end(),
 	pointer_to_binary_function<const Expr<int>, const Expr<int>, bool>(compare<>) );
 }
+
+// { dg-prune-output "enable_if" }