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C++ PATCH for c++/91129 - wrong error with binary op in template argument


We reject this test with errors like

nontype1.C:22:14: error: taking address of rvalue [-fpermissive]
   22 |   A<int, N / C<int, 6>{}> a2;
      |              ^~~~~~~~~~~

that happens because for converting "C<int, 6>{}" to int we generate
"C<int, 6>::operator int (&TARGET_EXPR <D.1234, {}>)".  The second
template argument is a binary operator, so while parsing the template
arguments in a function template foo we end up in cp_build_binary_op.

cp_build_binary_op calls, for certain binary ops, fold_non_dependent_expr.
Since <https://gcc.gnu.org/ml/gcc-patches/2018-06/msg01475.html> these
calls are no longer tf_none.  fold_non_dependent_expr, when in a template,
will instantiate, which gives the "taking address of rvalue" error.

In this particular case the fix seems to be using fold_for_warn instead,
which in a template is fold_non_dependent_expr with tf_none; all the
fold calls I'm changing in this patch are used for diagnostic purposes
only, and it fixes all the bogus errors.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2019-08-29  Marek Polacek  <polacek@redhat.com>

	PR c++/91129 - wrong error with binary op in template argument.
	* typeck.c (warn_for_null_address): Use fold_for_warn instead of
	fold_non_dependent_expr.
	(cp_build_binary_op): Likewise.

	* g++.dg/cpp1y/nontype1.C: New test.

diff --git gcc/cp/typeck.c gcc/cp/typeck.c
index c09bb309142..31414453524 100644
--- gcc/cp/typeck.c
+++ gcc/cp/typeck.c
@@ -4305,7 +4305,7 @@ warn_for_null_address (location_t location, tree op, tsubst_flags_t complain)
       || TREE_NO_WARNING (op))
     return;
 
-  tree cop = fold_non_dependent_expr (op, complain);
+  tree cop = fold_for_warn (op);
 
   if (TREE_CODE (cop) == ADDR_EXPR
       && decl_with_nonnull_addr_p (TREE_OPERAND (cop, 0))
@@ -4628,9 +4628,8 @@ cp_build_binary_op (const op_location_t &location,
 	      || code1 == COMPLEX_TYPE || code1 == VECTOR_TYPE))
 	{
 	  enum tree_code tcode0 = code0, tcode1 = code1;
-	  tree cop1 = fold_non_dependent_expr (op1, complain);
 	  doing_div_or_mod = true;
-	  warn_for_div_by_zero (location, cop1);
+	  warn_for_div_by_zero (location, fold_for_warn (op1));
 
 	  if (tcode0 == COMPLEX_TYPE || tcode0 == VECTOR_TYPE)
 	    tcode0 = TREE_CODE (TREE_TYPE (TREE_TYPE (op0)));
@@ -4669,11 +4668,8 @@ cp_build_binary_op (const op_location_t &location,
 
     case TRUNC_MOD_EXPR:
     case FLOOR_MOD_EXPR:
-      {
-	tree cop1 = fold_non_dependent_expr (op1, complain);
-	doing_div_or_mod = true;
-	warn_for_div_by_zero (location, cop1);
-      }
+      doing_div_or_mod = true;
+      warn_for_div_by_zero (location, fold_for_warn (op1));
 
       if (code0 == VECTOR_TYPE && code1 == VECTOR_TYPE
 	  && TREE_CODE (TREE_TYPE (type0)) == INTEGER_TYPE
@@ -4766,7 +4762,7 @@ cp_build_binary_op (const op_location_t &location,
 	}
       else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
 	{
-	  tree const_op1 = fold_non_dependent_expr (op1, complain);
+	  tree const_op1 = fold_for_warn (op1);
 	  if (TREE_CODE (const_op1) != INTEGER_CST)
 	    const_op1 = op1;
 	  result_type = type0;
@@ -4812,10 +4808,10 @@ cp_build_binary_op (const op_location_t &location,
 	}
       else if (code0 == INTEGER_TYPE && code1 == INTEGER_TYPE)
 	{
-	  tree const_op0 = fold_non_dependent_expr (op0, complain);
+	  tree const_op0 = fold_for_warn (op0);
 	  if (TREE_CODE (const_op0) != INTEGER_CST)
 	    const_op0 = op0;
-	  tree const_op1 = fold_non_dependent_expr (op1, complain);
+	  tree const_op1 = fold_for_warn (op1);
 	  if (TREE_CODE (const_op1) != INTEGER_CST)
 	    const_op1 = op1;
 	  result_type = type0;
diff --git gcc/testsuite/g++.dg/cpp1y/nontype1.C gcc/testsuite/g++.dg/cpp1y/nontype1.C
new file mode 100644
index 00000000000..a37e996a3ff
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp1y/nontype1.C
@@ -0,0 +1,42 @@
+// PR c++/91129 - wrong error with binary op in template argument.
+// { dg-do compile { target c++14 } }
+
+template<class T, T v>
+struct C
+{
+  constexpr operator T() const { return v; }
+  constexpr auto operator()() const { return v; }
+};
+
+template<class T, int N>
+struct A
+{
+};
+
+template<int N>
+void foo ()
+{
+  A<int, C<int, 6>{}> a0;
+  A<int, !C<int, 6>{}> a1;
+  A<int, N / C<int, 6>{}> a2;
+  A<int, N % C<int, 6>{}> a3;
+  A<int, N * C<int, 6>{}> a4;
+  A<int, N ^ C<int, 6>{}> a5;
+  A<int, N | C<int, 6>{}> a6;
+  A<int, N & C<int, 6>{}> a7;
+  A<int, N + C<int, 6>{}> a8;
+  A<int, N - C<int, 6>{}> a9;
+  A<int, -C<int, 6>{}> a10;
+  A<int, (N >> C<int, 6>{})> a11;
+  A<int, N << C<int, 6>{}> a12;
+  A<int, ~C<int, 6>{}> a13;
+  A<int, N || C<int, 6>{}> a14;
+  A<int, N && C<int, 6>{}> a15;
+  A<int, N == C<int, 6>{}> a16;
+  A<int, N != C<int, 6>{}> a17;
+}
+
+int main()
+{
+  foo<10>();
+}


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