[gcc r12-7363] c++: Add new test [PR79493]

[Marek Polacek]

https://gcc.gnu.org/g:cdcea7c1ef6586bb1eb0144b741969748cbd780b

commit r12-7363-gcdcea7c1ef6586bb1eb0144b741969748cbd780b
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Feb 23 12:46:21 2022 -0500

    c++: Add new test [PR79493]
    
    A nice side effect of r12-1822 was improving the diagnostic
    we emit for the following test.
    
            PR c++/79493
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/diagnostic/undeclared1.C: New test.

Diff:
---
 gcc/testsuite/g++.dg/diagnostic/undeclared1.C | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gcc/testsuite/g++.dg/diagnostic/undeclared1.C b/gcc/testsuite/g++.dg/diagnostic/undeclared1.C
new file mode 100644
index 00000000000..98c1ecb6581
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/undeclared1.C
@@ -0,0 +1,7 @@
+// PR c++/79493
+
+namespace A { }
+struct B {
+  void f(A::nonexistent param); // { dg-error ".A::nonexistent. has not been declared" }
+  void* g(A::nonexistent param); // { dg-error ".A::nonexistent. has not been declared" }
+};