c++: Fix mismatch in template argument deduction [PR90505]

2020-03-03  Jason Merrill  <jason@redhat.com>
	    Marek Polacek  <polacek@redhat.com>

	PR c++/90505 - mismatch in template argument deduction.
	* pt.c (tsubst): Don't reduce the template level of template
	parameters when tf_partial.

	* g++.dg/template/deduce4.C: New test.
	* g++.dg/template/deduce5.C: New test.
	* g++.dg/template/deduce6.C: New test.
	* g++.dg/template/deduce7.C: New test.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 80fb96ea9d3c6f18812bac9e9cdce2febbc0f24e..cb5211e5789a2889e23f98629440c65a053aa921 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2020-03-04  Jason Merrill  <jason@redhat.com>
+           Marek Polacek  <polacek@redhat.com>
+
+       PR c++/90505 - mismatch in template argument deduction.
+       * pt.c (tsubst): Don't reduce the template level of template
+       parameters when tf_partial.
+
 2020-03-04  Jason Merrill  <jason@redhat.com>
 
        PR c++/90432

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f233e78cc451b4490be8296939d365a0658691a1..2de9036b6471fc7235e099fbf26363ae6637f80c 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14630,6 +14630,11 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
             about the template parameter in question.  */
          return t;
 
+       /* Like with 'auto', don't reduce the level of template parameters
+          to avoid mismatches when deducing their types.  */
+       if (complain & tf_partial)
+         return t;
+
        /* If we get here, we must have been looking at a parm for a
           more deeply nested template.  Make a new version of this
           template parameter, but with a lower level.  */

diff --git a/gcc/testsuite/g++.dg/template/deduce4.C b/gcc/testsuite/g++.dg/template/deduce4.C
new file mode 100644 (file)
index 0000000..e2c165d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/deduce4.C
@@ -0,0 +1,17 @@
+// PR c++/90505 - mismatch in template argument deduction.
+// { dg-do compile }
+
+template <typename T>
+struct S {
+  template <typename U, typename V>
+  static void foo(V) { }
+
+  void bar () { foo<int>(10); }
+};
+
+void
+test ()
+{
+  S<int> s;
+  s.bar ();
+}

diff --git a/gcc/testsuite/g++.dg/template/deduce5.C b/gcc/testsuite/g++.dg/template/deduce5.C
new file mode 100644 (file)
index 0000000..9d382bf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/deduce5.C
@@ -0,0 +1,17 @@
+// PR c++/90505 - mismatch in template argument deduction.
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct S {
+  template <typename U, typename V = void>
+  static void foo(U) { }
+
+  void bar () { foo<int>(10); }
+};
+
+void
+test ()
+{
+  S<int> s;
+  s.bar ();
+}

diff --git a/gcc/testsuite/g++.dg/template/deduce6.C b/gcc/testsuite/g++.dg/template/deduce6.C
new file mode 100644 (file)
index 0000000..8fee612
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/deduce6.C
@@ -0,0 +1,17 @@
+// PR c++/90505 - mismatch in template argument deduction.
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct S {
+  template <typename U = int, typename V>
+  static void foo(V) { }
+
+  void bar () { foo<>(10); }
+};
+
+void
+test ()
+{
+  S<int> s;
+  s.bar ();
+}

diff --git a/gcc/testsuite/g++.dg/template/deduce7.C b/gcc/testsuite/g++.dg/template/deduce7.C
new file mode 100644 (file)
index 0000000..fbc28e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/deduce7.C
@@ -0,0 +1,10 @@
+// PR c++/90505 - mismatch in template argument deduction.
+// { dg-do compile { target c++11 } }
+
+template <typename> class a {
+  using b = int;
+  using c = int;
+  b d;
+  void e() { g<c>(d); }
+  template <typename... f> static void g(f...);
+};