In the testcase below, during ahead-of-time deduction of a constrained
auto inside a range-based for loop, we trip over an assert within
do_auto_deduction which expects the deduction context to be
adc_return_type or adc_variable_type, but do_range_for_auto_deduction
calls do_auto_deduction with the context defaulted to adc_unspecified.
We could safely relax the assert to also accept adc_unspecified, but it
seems the deduction context should really be adc_variable_type here.
gcc/cp/ChangeLog:
PR c++/99869
* parser.c (do_range_for_auto_deduction): Pass adc_variable_type
to do_auto_deduction.
gcc/testsuite/ChangeLog:
PR c++/99869
* g++.dg/cpp2a/concepts-placeholder6.C: New test.
RO_UNARY_STAR,
tf_warning_or_error);
TREE_TYPE (decl) = do_auto_deduction (TREE_TYPE (decl),
- iter_decl, auto_node);
+ iter_decl, auto_node,
+ tf_warning_or_error,
+ adc_variable_type);
}
}
}
--- /dev/null
+// PR c++/99869
+// { dg-do compile { target c++20 } }
+
+template <class T, class U> concept same_as = __is_same(T, U);
+
+template <class>
+void f() {
+ for (same_as<int> auto c : "") {} // { dg-error "constraint" }
+ for (same_as<char> auto c : "") {}
+}