c++: enum in generic lambda at global scope [PR105398]

We crash compiling this test since r11-7993 which changed
lookup_template_class_1 so that we only call tsubst_enum when

  !uses_template_parms (current_nonlambda_scope ())

But here current_nonlambda_scope () is the global NAMESPACE_DECL ::, which
doesn't have a type, therefore is considered type-dependent.  So we don't
call tsubst_enum, and crash in tsubst_copy/CONST_DECL because we didn't
find the e1 enumerator.

I don't think any namespace can depend on any template parameter, so
this patch tweaks uses_template_parms.

	PR c++/105398

gcc/cp/ChangeLog:

	* pt.cc (uses_template_parms): Return false for any NAMESPACE_DECL.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/lambda-generic-enum2.C: New test.

2 files changed, 16 insertions, 1 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 3cf1d7af8d2..e785c5db142 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -10905,7 +10905,7 @@ uses_template_parms (tree t)
 		   || uses_template_parms (TREE_CHAIN (t)));
   else if (TREE_CODE (t) == TYPE_DECL)
     dependent_p = dependent_type_p (TREE_TYPE (t));
-  else if (t == error_mark_node)
+  else if (t == error_mark_node || TREE_CODE (t) == NAMESPACE_DECL)
     dependent_p = false;
   else
     dependent_p = instantiation_dependent_expression_p (t);
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-enum2.C b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-enum2.C
new file mode 100644
index 00000000000..77cf0bb9d02
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-enum2.C
@@ -0,0 +1,15 @@
+// PR c++/105398
+// { dg-do compile { target c++14 } }
+
+auto f = [](auto &&m) {
+    enum E { _,e3,e2,e1,C4,C3,C2,C1 };
+    static constexpr int x_coeffs[3][4] = {
+        {e1,C2,C3,C4},
+        {e2,C1,C3,C4},
+        {e3,C1,C2,C4},
+    };
+};
+
+int main() {
+    f(0);
+}