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c++: Parameter pack in requires parameter list [PR94808]

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When printing the substituted parameter list of a requires-expression as
part of the "in requirements with ..." context line during concepts
diagnostics, we weren't considering that substitution into a parameter
pack can yield zero or multiple parameters.

This patch changes the way we print the parameter list of a
requires-expression in print_requires_expression_info.  We now print the
dependent form of the parameter list (along with its template parameter
mapping) instead of printing its substituted form.  Besides being an
improvement in its own, this also sidesteps the substitution issue in the
PR altogether.

gcc/cp/ChangeLog:

	PR c++/94808
	* error.c (print_requires_expression_info): Print the dependent
	form of the parameter list with its template parameter mapping,
	rather than printing the substituted form.

gcc/testsuite/ChangeLog:

	PR c++/94808
	* g++.dg/concepts/diagnostic12.C: New test.
	* g++.dg/concepts/diagnostic5.C: Adjust dg-message.
This commit is contained in:
Patrick Palka 2020-04-28 21:45:54 -04:00
parent 50a2f53562
commit 43439d5e84
5 changed files with 35 additions and 14 deletions
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7
gcc/cp/ChangeLog
View file

@ -1,3 +1,10 @@
2020-04-29 Patrick Palka <ppalka@redhat.com>
PR c++/94808
* error.c (print_requires_expression_info): Print the dependent
form of the parameter list with its template parameter mapping,
rather than printing the substituted form.
2020-04-28 Jason Merrill <jason@redhat.com>
PR c++/94583

16
gcc/cp/error.c
View file

@ -3746,7 +3746,6 @@ print_requires_expression_info (diagnostic_context *context, tree constr, tree a
map = tsubst_parameter_mapping (map, args, tf_none, NULL_TREE);
if (map == error_mark_node)
return;
args = get_mapped_args (map);
print_location (context, cp_expr_loc_or_input_loc (expr));
pp_verbatim (context->printer, "in requirements ");
@ -3756,19 +3755,12 @@ print_requires_expression_info (diagnostic_context *context, tree constr, tree a
pp_verbatim (context->printer, "with ");
while (parms)
{
tree next = TREE_CHAIN (parms);
TREE_CHAIN (parms) = NULL_TREE;
cp_unevaluated u;
tree p = tsubst (parms, args, tf_none, NULL_TREE);
pp_verbatim (context->printer, "%q#D", p);
TREE_CHAIN (parms) = next;
if (next)
pp_verbatim (context->printer, "%q#D", parms);
if (TREE_CHAIN (parms))
pp_separate_with_comma ((cxx_pretty_printer *)context->printer);
parms = next;
parms = TREE_CHAIN (parms);
}
pp_cxx_parameter_mapping ((cxx_pretty_printer *)context->printer, map);
pp_verbatim (context->printer, "\n");
}

6
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,9 @@
2020-04-29 Patrick Palka <ppalka@redhat.com>
PR c++/94808
* g++.dg/concepts/diagnostic12.C: New test.
* g++.dg/concepts/diagnostic5.C: Adjust dg-message.
2020-04-28 Alexandre Oliva <oliva@adacore.com>
PR target/94812

16
gcc/testsuite/g++.dg/concepts/diagnostic12.C Normal file
View file

@ -0,0 +1,16 @@
// PR c++/94808
// { dg-do compile { target concepts } }
template<typename T, typename... Args>
concept c1 = requires (T t, Args... args) { *t; };
// { dg-message "in requirements with .T t., .Args ... args. .with.* Args = \{\}" "" { target *-*-* } .-1 }
static_assert(c1<int>); // { dg-error "failed" }
void f(...);
template<typename... Args>
concept c2 = requires (Args... args) { f(*args...); };
// { dg-message "in requirements with .Args ... args. .with Args = \{int, char\}" "" { target *-*-* } .-1 }
static_assert(c2<int, char>); // { dg-error "failed" }

4
gcc/testsuite/g++.dg/concepts/diagnostic5.C
View file

@ -9,7 +9,7 @@ template<typename T>
template<typename T>
concept c2 = requires (T x) { *x; };
// { dg-message "satisfaction of .c2<T>. .with T = char." "" { target *-*-* } .-1 }
// { dg-message "in requirements with .char x." "" { target *-*-* } .-2 }
// { dg-message "in requirements with .T x. .with T = char." "" { target *-*-* } .-2 }
// { dg-message "required expression .* is invalid" "" { target *-*-* } .-3 }
template<typename T>
@ -25,7 +25,7 @@ template<typename T>
template<typename T>
concept c5 = requires (T x) { { &x } -> c1; };
// { dg-message "satisfaction of .c5<T>. .with T = char." "" { target *-*-* } .-1 }
// { dg-message "in requirements with .char x." "" { target *-*-* } .-2 }
// { dg-message "in requirements with .T x. .with T = char." "" { target *-*-* } .-2 }
template<typename T>
requires (c1<T> || c2<T>) || (c3<T> || c4<T>) || c5<T> // { dg-message "49: no operand" }