[gcc r11-9941] c++: enum in generic lambda at global scope [PR105398]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:3a1358e5f38864bf5688a7b6db1fda482321a77a

commit r11-9941-g3a1358e5f38864bf5688a7b6db1fda482321a77a
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Apr 26 16:12:58 2022 -0400

    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.c (uses_template_parms): Return false for any NAMESPACE_DECL.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp1y/lambda-generic-enum2.C: New test.
    
    (cherry picked from commit 409edcca331296b53842c50d3b789e1b1ccc05e5)

Diff:
---
 gcc/cp/pt.c                                       |  2 +-
 gcc/testsuite/g++.dg/cpp1y/lambda-generic-enum2.C | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 318d42d800d..92b2ab412d3 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10889,7 +10889,7 @@ 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);
+}