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c++: Some improvements to concept diagnostics

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This patch improves our concept diagnostics in two ways.  First, it sets a more
precise location for the constraint expressions built in
finish_constraint_binary_op.  As a result, when a disjunction is unsatisfied we
now print e.g.

.../include/bits/range_access.h:467:2: note: neither operand of the disjunction is satisfied
  466 |  requires is_bounded_array_v<remove_reference_t<_Tp>> || __member_end<_Tp>
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  467 |  || __adl_end<_Tp>
      |  ^~~~~~~~~~~~~~~~~

instead of

.../include/bits/range_access.h:467:2: note: neither operand of the disjunction is satisfied
  467 |  || __adl_end<_Tp>
      |  ^~

Second, this patch changes diagnose_atomic_constraint to print unsatisfied
atomic constraint expressions with their template arguments.  So e.g. we now
print

cpp2a/concepts-pr67719.C:9:8: note: the expression ‘(... &&(C<Tx>)()) [with Tx = {int, long int, void}]’ evaluated to ‘false’

instead of

cpp2a/concepts-pr67719.C:9:8: note: the expression ‘(... &&(C<Tx>)())’ evaluated to ‘false’

Tested on x86_64-pc-linux-gnu, and verified that all the diagnostics emitted in
our concept tests are no worse with this patch.

gcc/cp/ChangeLog:

	* constraint.cc (finish_constraint_binary_op): Set expr's location range
	to the range of its operands.
	(satisfy_atom): Pass MAP instead of ARGS to diagnose_atomic_constraint.
	(diagnose_trait_expr): Take the instantiated parameter mapping MAP
	instead of the corresponding template arguments ARGS and adjust body
	accordingly.
	(diagnose_requires_expr): Likewise.
	(diagnose_atomic_constraint): Likewise.  When printing an atomic
	constraint expression, print the instantiated parameter mapping
	alongside it.
	* cxx-pretty-print.cc (cxx_pretty_printer::expression)
	[NONTYPE_ARGUMENT_PACK]: Print braces around a NONTYPE_ARGUMENT_PACK.
	(cxx_pretty_printer::type_id): Handle TYPE_ARGUMENT_PACK.

gcc/testsuite/ChangeLog:

	* g++.dg/concepts/diagnostic2.C: New test.
	* g++.dg/concepts/diagnostic3.C: New test.
This commit is contained in:
Patrick Palka 2020-02-20 15:56:20 -05:00
parent 38e1002657
commit 44f6b7fb57
6 changed files with 116 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
gcc/cp/ChangeLog
View file

@ -1,3 +1,19 @@
2020-02-26 Patrick Palka <ppalka@redhat.com>
* constraint.cc (finish_constraint_binary_op): Set expr's location range
to the range of its operands.
(satisfy_atom): Pass MAP instead of ARGS to diagnose_atomic_constraint.
(diagnose_trait_expr): Take the instantiated parameter mapping MAP
instead of the corresponding template arguments ARGS and adjust body
accordingly.
(diagnose_requires_expr): Likewise.
(diagnose_atomic_constraint): Likewise. When printing an atomic
constraint expression, print the instantiated parameter mapping
alongside it.
* cxx-pretty-print.cc (cxx_pretty_printer::expression)
[NONTYPE_ARGUMENT_PACK]: Print braces around a NONTYPE_ARGUMENT_PACK.
(cxx_pretty_printer::type_id): Handle TYPE_ARGUMENT_PACK.
2020-02-26 Marek Polacek <polacek@redhat.com>
PR c++/93676 - value-init crash in template.

33
gcc/cp/constraint.cc
View file

@ -155,14 +155,14 @@ finish_constraint_binary_op (location_t loc,
if (!check_constraint_operands (loc, lhs, rhs))
return error_mark_node;
tree overload;
tree expr = build_x_binary_op (loc, code,
lhs, TREE_CODE (lhs),
rhs, TREE_CODE (rhs),
&overload, tf_none);
cp_expr expr = build_x_binary_op (loc, code,
lhs, TREE_CODE (lhs),
rhs, TREE_CODE (rhs),
&overload, tf_none);
/* When either operand is dependent, the overload set may be non-empty. */
if (expr == error_mark_node)
return error_mark_node;
SET_EXPR_LOCATION (expr, loc);
expr.set_range (lhs.get_start (), rhs.get_finish ());
return expr;
}
@ -2547,7 +2547,7 @@ satisfy_atom (tree t, tree args, subst_info info)
/* Compute the value of the constraint. */
result = satisfaction_value (cxx_constant_value (result));
if (result == boolean_false_node && info.noisy ())
diagnose_atomic_constraint (t, args, info);
diagnose_atomic_constraint (t, map, info);
return cache.save (result);
}
@ -3056,9 +3056,10 @@ get_constraint_error_location (tree t)
/* Emit a diagnostic for a failed trait. */
void
diagnose_trait_expr (tree expr, tree args)
diagnose_trait_expr (tree expr, tree map)
{
location_t loc = cp_expr_location (expr);
tree args = get_mapped_args (map);
/* Build a "fake" version of the instantiated trait, so we can
get the instantiated types from result. */
@ -3271,11 +3272,12 @@ diagnose_requirement (tree req, tree args, tree in_decl)
}
static void
diagnose_requires_expr (tree expr, tree args, tree in_decl)
diagnose_requires_expr (tree expr, tree map, tree in_decl)
{
local_specialization_stack stack (lss_copy);
tree parms = TREE_OPERAND (expr, 0);
tree body = TREE_OPERAND (expr, 1);
tree args = get_mapped_args (map);
cp_unevaluated u;
subst_info info (tf_warning_or_error, NULL_TREE);
@ -3292,11 +3294,11 @@ diagnose_requires_expr (tree expr, tree args, tree in_decl)
}
}
/* Diagnose a substitution failure in the atomic constraint T. Note that
ARGS have been previously instantiated through the parameter map. */
/* Diagnose a substitution failure in the atomic constraint T when applied
with the instantiated parameter mapping MAP. */
static void
diagnose_atomic_constraint (tree t, tree args, subst_info info)
diagnose_atomic_constraint (tree t, tree map, subst_info info)
{
/* If the constraint is already ill-formed, we've previously diagnosed
the reason. We should still say why the constraints aren't satisfied. */
@ -3320,17 +3322,20 @@ diagnose_atomic_constraint (tree t, tree args, subst_info info)
switch (TREE_CODE (expr))
{
case TRAIT_EXPR:
diagnose_trait_expr (expr, args);
diagnose_trait_expr (expr, map);
break;
case REQUIRES_EXPR:
diagnose_requires_expr (expr, args, info.in_decl);
diagnose_requires_expr (expr, map, info.in_decl);
break;
case INTEGER_CST:
/* This must be either 0 or false. */
inform (loc, "%qE is never satisfied", expr);
break;
default:
inform (loc, "the expression %qE evaluated to %<false%>", expr);
tree a = copy_node (t);
ATOMIC_CONSTR_MAP (a) = map;
inform (loc, "the expression %qE evaluated to %<false%>", a);
ggc_free (a);
}
}

17
gcc/cp/cxx-pretty-print.c
View file

@ -1214,12 +1214,14 @@ cxx_pretty_printer::expression (tree t)
{
tree args = ARGUMENT_PACK_ARGS (t);
int i, len = TREE_VEC_LENGTH (args);
pp_cxx_left_brace (this);
for (i = 0; i < len; ++i)
{
if (i > 0)
pp_cxx_separate_with (this, ',');
expression (TREE_VEC_ELT (args, i));
}
pp_cxx_right_brace (this);
}
break;
@ -1839,6 +1841,21 @@ cxx_pretty_printer::type_id (tree t)
pp_cxx_ws_string (this, "...");
break;
case TYPE_ARGUMENT_PACK:
{
tree args = ARGUMENT_PACK_ARGS (t);
int len = TREE_VEC_LENGTH (args);
pp_cxx_left_brace (this);
for (int i = 0; i < len; ++i)
{
if (i > 0)
pp_cxx_separate_with (this, ',');
type_id (TREE_VEC_ELT (args, i));
}
pp_cxx_right_brace (this);
}
break;
default:
c_pretty_printer::type_id (t);
break;

5
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2020-02-26 Patrick Palka <ppalka@redhat.com>
* g++.dg/concepts/diagnostic2.C: New test.
* g++.dg/concepts/diagnostic3.C: New test.
2020-02-26 Marek Polacek <polacek@redhat.com>
PR c++/93676 - value-init crash in template.

30
gcc/testsuite/g++.dg/concepts/diagnostic2.C Normal file
View file

@ -0,0 +1,30 @@
// { dg-do compile { target c++2a } }
// { dg-options "-fdiagnostics-show-caret" }
template<typename T>
inline constexpr bool foo_v = false;
template<typename T>
concept foo = foo_v<T> || foo_v<T&>; // { dg-message "neither operand" }
/* { dg-begin-multiline-output "" }
concept foo = foo_v<T> || foo_v<T&>;
~~~~~~~~~^~~~~~~~~~~~
{ dg-end-multiline-output "" } */
template<typename T>
requires foo<T>
void bar();
/* { dg-begin-multiline-output "" }
void bar();
{ dg-end-multiline-output "" } */
/* { dg-prune-output "~" } */
void
baz()
{
bar<int>(); // { dg-error "unsatisfied constraints" }
/* { dg-begin-multiline-output "" }
bar<int>();
^
{ dg-end-multiline-output "" } */
}

29
gcc/testsuite/g++.dg/concepts/diagnostic3.C Normal file
View file

@ -0,0 +1,29 @@
// { dg-do compile { target c++2a } }
template<typename T>
inline constexpr bool foo_v = false;
template<typename T>
concept foo = (bool)(foo_v<T> | foo_v<T&>);
template<typename... Ts>
requires (foo<Ts> && ...)
void
bar() // { dg-message "with Ts = .int, char... evaluated to .false." }
{ }
template<int>
struct S { };
template<int... Is>
requires (foo<S<Is>> && ...)
void
baz() // { dg-message "with Is = .2, 3, 4... evaluated to .false." }
{ }
void
baz()
{
bar<int, char>(); // { dg-error "unsatisfied constraints" }
baz<2,3,4>(); // { dg-error "unsatisfied constraints" }
}