diff mbox series

[pushed] c++: Fix constrained conversion op.

Message ID 20200228184430.14966-1-jason@redhat.com
State New
Headers show
Series [pushed] c++: Fix constrained conversion op. | expand

Commit Message

Jason Merrill Feb. 28, 2020, 6:44 p.m. UTC 
We don't want to promote a conversion from viable == 0 to viable == -1.
Found in ranges-v3.

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

gcc/cp/ChangeLog
2020-02-28  Jason Merrill  <jason@redhat.com>

	* call.c (build_user_type_conversion_1): Don't look at the second
	conversion of a non-viable candidate.
---
 gcc/cp/call.c                               |  4 ++++
 gcc/testsuite/g++.dg/cpp2a/concepts-conv1.C | 15 +++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-conv1.C


base-commit: 77e596cf3c1b7bc11ba946394ed8d62a49157b49
diff mbox series

Patch

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index e07ee85c06e..85bbd043a1d 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -4083,6 +4083,10 @@  build_user_type_conversion_1 (tree totype, tree expr, int flags,
 
       for (cand = candidates; cand != old_candidates; cand = cand->next)
 	{
+	  if (cand->viable == 0)
+	    /* Already rejected, don't change to -1.  */
+	    continue;
+
 	  tree rettype = TREE_TYPE (TREE_TYPE (cand->fn));
 	  conversion *ics
 	    = implicit_conversion (totype,
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-conv1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-conv1.C
new file mode 100644
index 00000000000..aa29acbcb13
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-conv1.C
@@ -0,0 +1,15 @@ 
+// { dg-do compile { target concepts } }
+
+template <class T> concept False = false;
+
+template <class T>
+struct A
+{
+  explicit operator bool ();
+  explicit operator bool () requires False<T>;
+};
+
+int main()
+{
+  int i { A<int>() };		// { dg-error "" }
+}