Re: [PATCH] c++: unifying constants vs their type [PR99186, PR104867]

[Jason Merrill]

On 12/12/23 16:21, Patrick Palka wrote:

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
for trunk?

OK.

-- >8 --

When unifying constants we need to generally treat constants of
different types but same value as different, in light of auto template
parameters.  This patch fixes this in a minimal way; it seems we could
get away with just using template_args_equal here, as we do in the
default case, but that's a simplification we could look into during next
stage 1.

        PR c++/99186
        PR c++/104867

gcc/cp/ChangeLog:

        * pt.cc (unify) <case INTEGER_CST>: Compare types as well.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp1z/nontype-auto23.C: New test.
        * g++.dg/cpp1z/nontype-auto24.C: New test.
---
  gcc/cp/pt.cc                                |  2 ++
  gcc/testsuite/g++.dg/cpp1z/nontype-auto23.C | 23 +++++++++++++++++++++
  gcc/testsuite/g++.dg/cpp1z/nontype-auto24.C | 18 ++++++++++++++++
  3 files changed, 43 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/cpp1z/nontype-auto23.C
  create mode 100644 gcc/testsuite/g++.dg/cpp1z/nontype-auto24.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a8966e223f1..602dd02d29d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -24709,6 +24709,8 @@ unify (tree tparms, tree targs, tree parm, tree arg, 
int strict,
        /* Type INTEGER_CST can come from ordinary constant template args.  */
      case INTEGER_CST:
      case REAL_CST:
+      if (!same_type_p (TREE_TYPE (parm), TREE_TYPE (arg)))
+       return unify_template_argument_mismatch (explain_p, parm, arg);
        while (CONVERT_EXPR_P (arg))
        arg = TREE_OPERAND (arg, 0);

diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto23.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto23.C

new file mode 100644
index 00000000000..467559ffdda
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto23.C
@@ -0,0 +1,23 @@
+// PR c++/99186
+// { dg-do compile { target c++17 } }
+
+template<int N, typename T, typename... U>
+struct tuple_impl : tuple_impl<N + 1, U...> { };
+
+template<int N, typename T>
+struct tuple_impl<N, T> { };
+
+template<typename T, typename U>
+struct tuple : tuple_impl<0, T, U> { };
+
+template<typename T, int N, typename... U>
+void get(const tuple_impl<N, T, U...>&);
+
+template<auto>
+struct S;
+
+int main() {
+   tuple<S<1>,S<1U>> x;
+   get<S<1U>>(x);
+   get<S<1>>(x);
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto24.C 
b/gcc/testsuite/g++.dg/cpp1z/nontype-auto24.C
new file mode 100644
index 00000000000..52e4c134ccd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto24.C
@@ -0,0 +1,18 @@
+// PR c++/104867
+// { dg-do compile { target c++17 } }
+
+enum class Foo { A1 };
+
+enum class Bar { B1 };
+
+template<auto EnumVal> struct enum_;
+
+template<class...> struct list { };
+
+template<class V> void f(list<enum_<Bar::B1>, V>);
+
+struct enum_type_map : list<enum_<Foo::A1>, int>, list<enum_<Bar::B1>, double> 
{ };
+
+int main() {
+  f(enum_type_map());
+}