From 661232da72d29f8f2385d5f588727beb74360144 Mon Sep 17 00:00:00 2001
From: Marek Polacek <polacek@redhat.com>
Date: Mon, 11 May 2020 18:28:19 -0400
Subject: [PATCH] c++: explicit(bool) malfunction with dependent expression
 [PR95066]

I forgot to set DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P when merging two
function declarations and as a sad consequence, we never tsubsted
the dependent explicit-specifier in tsubst_function_decl, leading to
disregarding the explicit-specifier altogether, and wrongly accepting
this test.

	PR c++/95066
	* decl.c (duplicate_decls): Set DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P.

	* g++.dg/cpp2a/explicit16.C: New test.
---
 gcc/cp/ChangeLog                        |  5 +++++
 gcc/cp/decl.c                           |  2 ++
 gcc/testsuite/ChangeLog                 |  5 +++++
 gcc/testsuite/g++.dg/cpp2a/explicit16.C | 21 +++++++++++++++++++++
 4 files changed, 33 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/explicit16.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2e5351475af..145a5d577bb 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-13  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/95066
+	* decl.c (duplicate_decls): Set DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P.
+
 2020-05-13  Nathan Sidwell  <nathan@acm.org>
 
 	* pt.c (template_args_equal): Reorder category checking for
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 37ab4818486..7c7ca1ff1c0 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -2035,6 +2035,8 @@ duplicate_decls (tree newdecl, tree olddecl, bool newdecl_is_friend)
       DECL_FINAL_P (newdecl) |= DECL_FINAL_P (olddecl);
       DECL_OVERRIDE_P (newdecl) |= DECL_OVERRIDE_P (olddecl);
       DECL_THIS_STATIC (newdecl) |= DECL_THIS_STATIC (olddecl);
+      DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P (newdecl)
+	|= DECL_HAS_DEPENDENT_EXPLICIT_SPEC_P (olddecl);
       if (DECL_OVERLOADED_OPERATOR_P (olddecl))
 	DECL_OVERLOADED_OPERATOR_CODE_RAW (newdecl)
 	  = DECL_OVERLOADED_OPERATOR_CODE_RAW (olddecl);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cd1fa6e2237..e2dea4dfecb 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-13  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/95066
+	* g++.dg/cpp2a/explicit16.C: New test.
+
 2020-05-13  Jason Merrill  <jason@redhat.com>
 
 	* lib/target-supports.exp (check_effective_target_c++20_only)
diff --git a/gcc/testsuite/g++.dg/cpp2a/explicit16.C b/gcc/testsuite/g++.dg/cpp2a/explicit16.C
new file mode 100644
index 00000000000..9d95b0d669e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/explicit16.C
@@ -0,0 +1,21 @@
+// PR c++/95066 - explicit malfunction with dependent expression.
+// { dg-do compile { target c++2a } }
+
+template <typename T>
+struct Foo {
+  template <typename U>
+  explicit(static_cast<U>(true)) operator Foo<U>();
+};
+
+template <typename T>
+template <typename U>
+Foo<T>::operator Foo<U>() {
+  return {};
+}
+
+int
+main ()
+{
+  Foo<float> a;
+  Foo<int> b = a; // { dg-error "conversion" }
+}
-- 
2.30.2