C++ PATCH for c++/82219, -Wignored-qualifiers and template

[Jason Merrill]

Many warnings don't make as much sense in template instantiations, this is one.

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

commit 0b86d1edf07a3abea46c1bdf9a019141a83759b4
Author: Jason Merrill <ja...@redhat.com>
Date:   Thu Nov 30 11:56:37 2017 -0500

            PR c++/82219 - bogus -Wignored-qualifiers with template
    
            * pt.c (tsubst_copy_and_build) [STATIC_CAST_EXPR]: Suppress
            -Wignored-qualifiers.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 7e2f7740106..500ac0c64fe 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -17180,6 +17180,7 @@ tsubst_copy_and_build (tree t,
        op = RECUR (TREE_OPERAND (t, 0));
 
        warning_sentinel s(warn_useless_cast);
+       warning_sentinel s2(warn_ignored_qualifiers);
        switch (TREE_CODE (t))
          {
          case CAST_EXPR:
diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers1.C 
b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers1.C
new file mode 100644
index 00000000000..5be61a6f394
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers1.C
@@ -0,0 +1,8 @@
+// PR c++/82219
+// { dg-additional-options "-Wall -Wextra" }
+
+struct A {
+  template <typename T> T foo(T *) const { return static_cast<T>(0); }
+  void bar() const { foo(&i); }
+  int i;
+};