diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 0790bbf948f..838179d5fe3 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -151,7 +151,7 @@ static tree get_partial_spec_bindings (tree, tree, tree); static void tsubst_enum (tree, tree, tree); static bool check_instantiated_args (tree, tree, tsubst_flags_t); static int check_non_deducible_conversion (tree, tree, unification_kind_t, int, - struct conversion **, bool); + struct conversion **, bool, bool); static int maybe_adjust_types_for_deduction (tree, unification_kind_t, tree*, tree*, tree); static int type_unification_real (tree, tree, tree, const tree *, @@ -22321,7 +22321,8 @@ pack_deducible_p (tree parm, tree fn) static int check_non_deducible_conversions (tree parms, const tree *args, unsigned nargs, tree fn, unification_kind_t strict, int flags, - struct conversion **convs, bool explain_p) + struct conversion **convs, bool explain_p, + bool noninst_only_p) { /* Non-constructor methods need to leave a conversion for 'this', which isn't included in nargs here. */ @@ -22357,7 +22358,7 @@ check_non_deducible_conversions (tree parms, const tree *args, unsigned nargs, int lflags = conv_flags (ia, nargs, fn, arg, flags); if (check_non_deducible_conversion (parm, arg, strict, lflags, - conv_p, explain_p)) + conv_p, explain_p, noninst_only_p)) return 1; } @@ -22657,6 +22658,16 @@ fn_type_unification (tree fn, deduced: + /* As a refinement of CWG2369, check first and foremost non-dependent + conversions that we know are not going to induce template instantiation + (PR99599). */ + if (strict == DEDUCE_CALL + && incomplete + && check_non_deducible_conversions (parms, args, nargs, fn, strict, flags, + convs, explain_p, + /*noninst_only_p=*/true)) + goto fail; + /* CWG2369: Check satisfaction before non-deducible conversions. */ if (!constraints_satisfied_p (fn, targs)) { @@ -22670,7 +22681,8 @@ fn_type_unification (tree fn, as the standard says that we substitute explicit args immediately. */ if (incomplete && check_non_deducible_conversions (parms, args, nargs, fn, strict, flags, - convs, explain_p)) + convs, explain_p, + /*noninst_only_p=*/false)) goto fail; /* All is well so far. Now, check: @@ -22897,6 +22909,59 @@ maybe_adjust_types_for_deduction (tree tparms, return result; } +/* Return true if computing a conversion from FROM to TO might induce template + instantiation. Conversely, if this predicate returns false then computing + the conversion definitely won't induce template instantiation. */ + +static bool +conversion_may_instantiate_p (tree to, tree from) +{ + to = non_reference (to); + from = non_reference (from); + + bool ptr_conv_p = false; + if (TYPE_PTR_P (to) + && TYPE_PTR_P (from)) + { + to = TREE_TYPE (to); + from = TREE_TYPE (from); + ptr_conv_p = true; + } + + /* If one of the types is a not-yet-instantiated class template + specialization, then computing the conversion might instantiate + it in order to inspect bases, conversion functions and/or + converting constructors. */ + if ((CLASS_TYPE_P (to) + && !COMPLETE_TYPE_P (to) + && CLASSTYPE_TEMPLATE_INSTANTIATION (to)) + || (CLASS_TYPE_P (from) + && !COMPLETE_TYPE_P (from) + && CLASSTYPE_TEMPLATE_INSTANTIATION (from))) + return true; + + /* Converting from one pointer type to another, or between + reference-related types, always yields a standard conversion. */ + if (ptr_conv_p || reference_related_p (to, from)) + return false; + + /* Converting to a non-aggregate class type will consider its + user-declared constructors, which might induce instantiation. */ + if (CLASS_TYPE_P (to) + && CLASSTYPE_NON_AGGREGATE (to)) + return true; + + /* Similarly, converting from a class type will consider its conversion + functions. */ + if (CLASS_TYPE_P (from) + && TYPE_HAS_CONVERSION (from)) + return true; + + /* Otherwise, computing this conversion definitely won't induce + template instantiation. */ + return false; +} + /* Subroutine of fn_type_unification. PARM is a function parameter of a template which doesn't contain any deducible template parameters; check if ARG is a suitable match for it. STRICT, FLAGS and EXPLAIN_P are as in @@ -22905,7 +22970,7 @@ maybe_adjust_types_for_deduction (tree tparms, static int check_non_deducible_conversion (tree parm, tree arg, unification_kind_t strict, int flags, struct conversion **conv_p, - bool explain_p) + bool explain_p, bool noninst_only_p) { tree type; @@ -22925,6 +22990,18 @@ check_non_deducible_conversion (tree parm, tree arg, unification_kind_t strict, } else if (strict == DEDUCE_CALL) { + if (conv_p && *conv_p) + { + /* This conversion was already computed earlier (when + computing only non-instantiating conversions). */ + gcc_checking_assert (!noninst_only_p); + return unify_success (explain_p); + } + + if (noninst_only_p + && conversion_may_instantiate_p (parm, type)) + return unify_success (explain_p); + bool ok = false; tree conv_arg = TYPE_P (arg) ? NULL_TREE : arg; if (conv_p) diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-nondep4.C b/gcc/testsuite/g++.dg/cpp2a/concepts-nondep4.C new file mode 100644 index 00000000000..9a8db55359f --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-nondep4.C @@ -0,0 +1,16 @@ +// PR c++/99599 +// { dg-do compile { target c++20 } } + +struct foo_tag { }; +struct bar_tag { }; + +template +concept fooable = requires(T it) { invoke_tag(foo_tag{}, it); }; + +template void invoke_tag(foo_tag, T); +template void invoke_tag(bar_tag, T) requires fooable; + +int main() { + invoke_tag(foo_tag{}, 0); + invoke_tag(bar_tag{}, 0); +} diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C index 18d126e05ea..08f206d3634 100644 --- a/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-recursive-sat4.C @@ -1,3 +1,4 @@ +// Verify we diagnose constraint recursion. // PR c++/96840 // { dg-do compile { target c++20 } } @@ -6,6 +7,7 @@ template concept C = requires(T t, U u) { t * u; }; // { dg-error "depends on itself" "" { target *-*-* } .-2 } template struct Int { + Int(); // make the class non-aggregate in light of PR99599 fix template requires C friend void operator*(T, Int) { } template requires C friend void operator*(Int, T) { } };