C++ PATCH for c++/84098, ICE with lambda in template NSDMI

[Jason Merrill]

When instantiating the members of a class template, we don't need to
consider lambdas, as instantiating them will be handled when we get to
tsubst_lambda_expr.  And now the new assert catches places we were
failing to ignore them, as here.

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

commit d97240d44096258f2c5218560861631b908d1024
Author: Jason Merrill <ja...@redhat.com>
Date:   Mon Jan 29 17:31:42 2018 -0500

            PR c++/84098 - ICE with lambda in template NSDMI.
    
            * pt.c (instantiate_class_template_1): Ignore more lambdas.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6c5d06b9ebb..9516be893aa 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10527,6 +10527,11 @@ instantiate_class_template_1 (tree type)
        {
          if (TYPE_P (t))
            {
+             if (LAMBDA_TYPE_P (t))
+               /* A closure type for a lambda in an NSDMI or default argument.
+                  Ignore it; it will be regenerated when needed.  */
+               continue;
+
              /* Build new CLASSTYPE_NESTED_UTDS.  */
 
              tree newtag;
@@ -10594,11 +10599,10 @@ instantiate_class_template_1 (tree type)
                  && DECL_OMP_DECLARE_REDUCTION_P (r))
                cp_check_omp_declare_reduction (r);
            }
-         else if (DECL_CLASS_TEMPLATE_P (t)
+         else if ((DECL_CLASS_TEMPLATE_P (t) || DECL_IMPLICIT_TYPEDEF_P (t))
                   && LAMBDA_TYPE_P (TREE_TYPE (t)))
-           /* A closure type for a lambda in a default argument for a
-              member template.  Ignore it; it will be instantiated with
-              the default argument.  */;
+           /* A closure type for a lambda in an NSDMI or default argument.
+              Ignore it; it will be regenerated when needed.  */;
          else
            {
              /* Build new TYPE_FIELDS.  */
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-lambda19.C 
b/gcc/testsuite/g++.dg/cpp1z/constexpr-lambda19.C
new file mode 100644
index 00000000000..a16d31c59eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-lambda19.C
@@ -0,0 +1,13 @@
+// PR c++/84098
+// { dg-options -std=c++17 }
+
+struct A{};
+
+template < typename >
+struct Test{
+    static constexpr auto var = []{};
+};
+
+int main(){
+    (void)Test< A >::var;
+}