| Message ID | 20221202194228.3794597-1-ppalka@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: unexpanded pack in requires-expr parm list [PR107417] | expand |
On 12/2/22 14:42, Patrick Palka wrote: > Here find_parameter_packs_r isn't recognizing the unexpanded pack T > inside the requires-expr's parameter list ultimately because > cp_walk_trees avoids walking the parameters, for good reason: in > > requires (Ts... ts) { } > > walking 'ts' would trigger a false positive in the unexpanded pack > checker since it's, well, an unexpanded pack. But we might as well walk > the TREE_TYPE of each parameter still, which for_each_template_parm_r > already does. > > Bootstrapped and regtested on x86_64-pc-linux-gne, does this look OK for > trunk/12? OK. > PR c++/107417 > > gcc/cp/ChangeLog: > > * pt.cc (for_each_template_parm_r) <case REQUIRES_EXPR>: Move > walking of the TREE_TYPE of each parameter to ... > * tree.cc (cp_walk_subtrees) <case REQUIRES_EXPR>: ... here. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp2a/concepts-requires33.C: New test. > --- > gcc/cp/pt.cc | 15 -------------- > gcc/cp/tree.cc | 20 ++++++++++--------- > .../g++.dg/cpp2a/concepts-requires33.C | 11 ++++++++++ > 3 files changed, 22 insertions(+), 24 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc > index bc8ea06ceae..80110da2d8a 100644 > --- a/gcc/cp/pt.cc > +++ b/gcc/cp/pt.cc > @@ -10573,21 +10573,6 @@ for_each_template_parm_r (tree *tp, int *walk_subtrees, void *d) > return error_mark_node; > break; > > - case REQUIRES_EXPR: > - { > - if (!fn) > - return error_mark_node; > - > - /* Recursively walk the type of each constraint variable. */ > - tree p = TREE_OPERAND (t, 0); > - while (p) > - { > - WALK_SUBTREE (TREE_TYPE (p)); > - p = TREE_CHAIN (p); > - } > - } > - break; > - > default: > break; > } > diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc > index 04a055d9d77..e9b6921df6a 100644 > --- a/gcc/cp/tree.cc > +++ b/gcc/cp/tree.cc > @@ -5603,15 +5603,17 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func, > break; > > case REQUIRES_EXPR: > - // Only recurse through the nested expression. Do not > - // walk the parameter list. Doing so causes false > - // positives in the pack expansion checker since the > - // requires parameters are introduced as pack expansions. > - ++cp_unevaluated_operand; > - result = cp_walk_tree (&REQUIRES_EXPR_REQS (*tp), func, data, pset); > - --cp_unevaluated_operand; > - *walk_subtrees_p = 0; > - break; > + { > + cp_unevaluated u; > + for (tree parm = REQUIRES_EXPR_PARMS (*tp); parm; parm = DECL_CHAIN (parm)) > + /* Walk the types of each parameter, but not the parameter itself. > + Doing so would cause false positives in the unexpanded parameter > + pack checker since a introduced parameter pack is bare. */ > + WALK_SUBTREE (TREE_TYPE (parm)); > + WALK_SUBTREE (REQUIRES_EXPR_REQS (*tp)); > + *walk_subtrees_p = 0; > + break; > + } > > case DECL_EXPR: > /* User variables should be mentioned in BIND_EXPR_VARS > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C > new file mode 100644 > index 00000000000..d07ae6dee7b > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C > @@ -0,0 +1,11 @@ > +// PR c++/107417 > +// { dg-do compile { target c++20 } } > + > +template<typename... T> > +requires (requires (T x) { true; } && ...) > +void f(); > + > +int main() { > + f<int>(); > + f<int, void>(); // { dg-error "no match" } > +}
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index bc8ea06ceae..80110da2d8a 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -10573,21 +10573,6 @@ for_each_template_parm_r (tree *tp, int *walk_subtrees, void *d) return error_mark_node; break; - case REQUIRES_EXPR: - { - if (!fn) - return error_mark_node; - - /* Recursively walk the type of each constraint variable. */ - tree p = TREE_OPERAND (t, 0); - while (p) - { - WALK_SUBTREE (TREE_TYPE (p)); - p = TREE_CHAIN (p); - } - } - break; - default: break; } diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index 04a055d9d77..e9b6921df6a 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -5603,15 +5603,17 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func, break; case REQUIRES_EXPR: - // Only recurse through the nested expression. Do not - // walk the parameter list. Doing so causes false - // positives in the pack expansion checker since the - // requires parameters are introduced as pack expansions. - ++cp_unevaluated_operand; - result = cp_walk_tree (&REQUIRES_EXPR_REQS (*tp), func, data, pset); - --cp_unevaluated_operand; - *walk_subtrees_p = 0; - break; + { + cp_unevaluated u; + for (tree parm = REQUIRES_EXPR_PARMS (*tp); parm; parm = DECL_CHAIN (parm)) + /* Walk the types of each parameter, but not the parameter itself. + Doing so would cause false positives in the unexpanded parameter + pack checker since a introduced parameter pack is bare. */ + WALK_SUBTREE (TREE_TYPE (parm)); + WALK_SUBTREE (REQUIRES_EXPR_REQS (*tp)); + *walk_subtrees_p = 0; + break; + } case DECL_EXPR: /* User variables should be mentioned in BIND_EXPR_VARS diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C new file mode 100644 index 00000000000..d07ae6dee7b --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C @@ -0,0 +1,11 @@ +// PR c++/107417 +// { dg-do compile { target c++20 } } + +template<typename... T> +requires (requires (T x) { true; } && ...) +void f(); + +int main() { + f<int>(); + f<int, void>(); // { dg-error "no match" } +}
Here find_parameter_packs_r isn't recognizing the unexpanded pack T inside the requires-expr's parameter list ultimately because cp_walk_trees avoids walking the parameters, for good reason: in requires (Ts... ts) { } walking 'ts' would trigger a false positive in the unexpanded pack checker since it's, well, an unexpanded pack. But we might as well walk the TREE_TYPE of each parameter still, which for_each_template_parm_r already does. Bootstrapped and regtested on x86_64-pc-linux-gne, does this look OK for trunk/12? PR c++/107417 gcc/cp/ChangeLog: * pt.cc (for_each_template_parm_r) <case REQUIRES_EXPR>: Move walking of the TREE_TYPE of each parameter to ... * tree.cc (cp_walk_subtrees) <case REQUIRES_EXPR>: ... here. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-requires33.C: New test. --- gcc/cp/pt.cc | 15 -------------- gcc/cp/tree.cc | 20 ++++++++++--------- .../g++.dg/cpp2a/concepts-requires33.C | 11 ++++++++++ 3 files changed, 22 insertions(+), 24 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires33.C