From adc06f45fbef12b06cdbb5603a372d82dca1baec Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Fri, 5 Apr 2019 21:22:40 +0000
Subject: [PATCH] PR c++/87145 - bogus error converting class type in template
 arg list.

	* pt.c (convert_nontype_argument): Don't call
	build_converted_constant_expr if it could involve calling a conversion
	function with a instantiation-dependent constructor as its argument.

	* g++.dg/cpp0x/constexpr-conv3.C: New test.
	* g++.dg/cpp0x/constexpr-conv4.C: New test.

From-SVN: r270178
---
 gcc/cp/ChangeLog                             |  7 ++++++
 gcc/cp/pt.c                                  | 13 ++++++++++
 gcc/testsuite/ChangeLog                      |  6 +++++
 gcc/testsuite/g++.dg/cpp0x/constexpr-conv3.C | 25 ++++++++++++++++++++
 gcc/testsuite/g++.dg/cpp0x/constexpr-conv4.C | 25 ++++++++++++++++++++
 5 files changed, 76 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-conv3.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-conv4.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 17c9aa712aa..f766f476f10 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2019-04-05  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87145 - bogus error converting class type in template arg list.
+	* pt.c (convert_nontype_argument): Don't call
+	build_converted_constant_expr if it could involve calling a conversion
+	function with a instantiation-dependent constructor as its argument.
+
 2019-04-05  Martin Sebor  <msebor@redhat.com>
 
 	PR bootstrap/89980
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 40d954d1e8a..f8001317bda 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6837,6 +6837,19 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
       else if (INTEGRAL_OR_ENUMERATION_TYPE_P (type)
 	       || cxx_dialect >= cxx17)
 	{
+	  /* Calling build_converted_constant_expr might create a call to
+	     a conversion function with a value-dependent argument, which
+	     could invoke taking the address of a temporary representing
+	     the result of the conversion.  */
+	  if (COMPOUND_LITERAL_P (expr)
+	      && CONSTRUCTOR_IS_DEPENDENT (expr)
+	      && MAYBE_CLASS_TYPE_P (expr_type)
+	      && TYPE_HAS_CONVERSION (expr_type))
+	    {
+	      expr = build1 (IMPLICIT_CONV_EXPR, type, expr);
+	      IMPLICIT_CONV_EXPR_NONTYPE_ARG (expr) = true;
+	      return expr;
+	    }
 	  /* C++17: A template-argument for a non-type template-parameter shall
 	     be a converted constant expression (8.20) of the type of the
 	     template-parameter.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index dc6f911fc4f..b854b575077 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-04-05  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/87145 - bogus error converting class type in template arg list.
+	* g++.dg/cpp0x/constexpr-conv3.C: New test.
+	* g++.dg/cpp0x/constexpr-conv4.C: New test.
+
 2019-04-05  Martin Sebor  <msebor@redhat.com>
 
 	PR bootstrap/89980
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-conv3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-conv3.C
new file mode 100644
index 00000000000..3f47c58cd2a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-conv3.C
@@ -0,0 +1,25 @@
+// PR c++/87145
+// { dg-do compile { target c++11 } }
+
+template<typename T, T t> struct integral_constant {
+  static constexpr T value = t;
+};
+
+enum class Enum : unsigned {};
+
+struct Pod {
+  unsigned val;
+
+  constexpr operator Enum() const {
+    return static_cast<Enum>(val);
+  }
+};
+
+template<unsigned N>
+constexpr void foo() {
+  using Foo = integral_constant<Enum, Pod{N}>;
+}
+
+int main() {
+  foo<2>();
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-conv4.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-conv4.C
new file mode 100644
index 00000000000..f4e3f00a585
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-conv4.C
@@ -0,0 +1,25 @@
+// PR c++/87145
+// { dg-do compile { target c++11 } }
+
+struct S {
+  int val;
+
+  constexpr operator int() const {
+    return static_cast<int>(val);
+  }
+};
+
+template<int N>
+struct F { };
+
+template<unsigned N>
+constexpr void foo() {
+  F<int{N}> f;
+  F<S{N}> f2;
+}
+
+int
+main()
+{
+  foo<2>();
+}
-- 
2.30.2