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* [gcc r11-7963] c++: placeholder type constraint inside range-for [PR99869]
@ 2021-04-02 23:57 Patrick Palka
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From: Patrick Palka @ 2021-04-02 23:57 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:260caabe10cde0158b87968a3bac85575301dafa
commit r11-7963-g260caabe10cde0158b87968a3bac85575301dafa
Author: Patrick Palka <ppalka@redhat.com>
Date: Fri Apr 2 19:46:24 2021 -0400
c++: placeholder type constraint inside range-for [PR99869]
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.
Diff:
---
gcc/cp/parser.c | 4 +++-
gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C | 10 ++++++++++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index d0477c42afe..808e5b61b1e 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -12878,7 +12878,9 @@ do_range_for_auto_deduction (tree decl, tree range_expr)
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);
}
}
}
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C
new file mode 100644
index 00000000000..fe1e3927129
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C
@@ -0,0 +1,10 @@
+// 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 : "") {}
+}
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