c++: Don't add built-in operator for ++ on bool.

This feels extremely obscure but at least it's an opportunity to fix the
comments.  P0002R1 removed deprecated operator++(bool) in C++17 so let's
avoid adding a builtin overload candidate for ++ when the type is bool.

	* call.c (add_builtin_candidate): Don't create a builtin overload
	candidate for ++ when type is bool in C++17.

	* g++.dg/overload/builtin5.C: New test.

4 files changed, 42 insertions, 8 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 98c2823..e9cd3eb 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,4 +1,9 @@
-2020-05-17  Marek Polacek  <polacek@redhat.com>
+2020-05-18  Marek Polacek  <polacek@redhat.com>
+
+	* call.c (add_builtin_candidate): Don't create a builtin overload
+	candidate for ++ when type is bool in C++17.
+
+2020-05-18  Marek Polacek  <polacek@redhat.com>
 
 	* cfns.h: Regenerated.
 
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index c587197..b96bc06 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -2672,19 +2672,19 @@ add_builtin_candidate (struct z_candidate **candidates, enum tree_code code,
   switch (code)
     {
 
-/* 4 For every pair T, VQ), where T is an arithmetic or  enumeration  type,
+/* 4 For every pair (T, VQ), where T is an arithmetic type other than bool,
      and  VQ  is  either  volatile or empty, there exist candidate operator
      functions of the form
 	     VQ T&   operator++(VQ T&);
 	     T       operator++(VQ T&, int);
-   5 For every pair T, VQ), where T is an enumeration type or an arithmetic
-     type  other than bool, and VQ is either volatile or empty, there exist
-     candidate operator functions of the form
+   5 For every pair (T, VQ), where T is an arithmetic type other than bool,
+     and VQ is either volatile or empty, there exist candidate operator
+     functions of the form
 	     VQ T&   operator--(VQ T&);
 	     T       operator--(VQ T&, int);
-   6 For every pair T, VQ), where T is  a  cv-qualified  or  cv-unqualified
-     complete  object type, and VQ is either volatile or empty, there exist
-     candidate operator functions of the form
+   6 For every pair (T, VQ), where T is a cv-qualified or cv-unqualified object
+     type, and VQ is either volatile or empty, there exist candidate operator
+     functions of the form
 	     T*VQ&   operator++(T*VQ&);
 	     T*VQ&   operator--(T*VQ&);
 	     T*      operator++(T*VQ&, int);
@@ -2697,6 +2697,10 @@ add_builtin_candidate (struct z_candidate **candidates, enum tree_code code,
       /* FALLTHRU */
     case POSTINCREMENT_EXPR:
     case PREINCREMENT_EXPR:
+      /* P0002R1, Remove deprecated operator++(bool) added "other than bool"
+	 to p4.  */
+      if (TREE_CODE (type1) == BOOLEAN_TYPE && cxx_dialect >= cxx17)
+	return;
       if (ARITHMETIC_TYPE_P (type1) || TYPE_PTROB_P (type1))
 	{
 	  type1 = build_reference_type (type1);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ad5b28d..0b5e1d3 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-18  Marek Polacek  <polacek@redhat.com>
+
+	* g++.dg/overload/builtin5.C: New test.
+
 2020-05-18  Doug Rupp  <rupp@adacore.com>
 
 	* gcc.target/powerpc/pr71763.c: Require powerpc_vsx_ok.
diff --git a/gcc/testsuite/g++.dg/overload/builtin5.C b/gcc/testsuite/g++.dg/overload/builtin5.C
new file mode 100644
index 0000000..a30251d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/overload/builtin5.C
@@ -0,0 +1,21 @@
+// { dg-do compile { target c++17 } }
+// Don't add built-in operator for ++ on bool.
+
+template<typename T>
+struct S { operator T&(); };
+
+template<int> void
+foo (S<bool>& s)
+{
+  --s; // { dg-error "no match for" }
+  ++s; // { dg-error "no match for" }
+  s++; // { dg-error "declared for postfix" }
+  s--; // { dg-error "declared for postfix" }
+}
+
+void
+bar ()
+{
+  S<bool> s;
+  foo<0> (s);
+}