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* [gcc r12-7600] c++: Don't allow type-constraint auto(x) [PR104752]
@ 2022-03-10 16:22 Marek Polacek
0 siblings, 0 replies; only message in thread
From: Marek Polacek @ 2022-03-10 16:22 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:97f76b5fc4b637033229e53033b4f8b6dc23472c
commit r12-7600-g97f76b5fc4b637033229e53033b4f8b6dc23472c
Author: Marek Polacek <polacek@redhat.com>
Date: Wed Mar 2 12:12:33 2022 -0500
c++: Don't allow type-constraint auto(x) [PR104752]
104752 points out that
template<class T>
concept C = true;
auto y = C auto(1);
is ill-formed as per [dcl.type.auto.deduct]: "For an explicit type conversion,
T is the specified type, which shall be auto." which doesn't allow
type-constraint auto.
PR c++/104752
gcc/cp/ChangeLog:
* semantics.cc (finish_compound_literal): Disallow auto{x} for
is_constrained_auto.
* typeck2.cc (build_functional_cast_1): Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/auto-fncast12.C: New test.
Diff:
---
gcc/cp/semantics.cc | 8 +++++++-
gcc/cp/typeck2.cc | 8 +++++++-
gcc/testsuite/g++.dg/cpp23/auto-fncast12.C | 8 ++++++++
3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 799ce943279..21740064d3d 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -3150,7 +3150,13 @@ finish_compound_literal (tree type, tree compound_literal,
&& !AUTO_IS_DECLTYPE (type)
&& CONSTRUCTOR_NELTS (compound_literal) == 1)
{
- if (cxx_dialect < cxx23)
+ if (is_constrained_auto (type))
+ {
+ if (complain & tf_error)
+ error ("%<auto{x}%> cannot be constrained");
+ return error_mark_node;
+ }
+ else if (cxx_dialect < cxx23)
pedwarn (input_location, OPT_Wc__23_extensions,
"%<auto{x}%> only available with "
"%<-std=c++2b%> or %<-std=gnu++2b%>");
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 39d03e4c3c4..a4c825fc34d 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -2308,7 +2308,13 @@ build_functional_cast_1 (location_t loc, tree exp, tree parms,
&& list_length (parms) == 1)
{
init = TREE_VALUE (parms);
- if (cxx_dialect < cxx23)
+ if (is_constrained_auto (anode))
+ {
+ if (complain & tf_error)
+ error_at (loc, "%<auto(x)%> cannot be constrained");
+ return error_mark_node;
+ }
+ else if (cxx_dialect < cxx23)
pedwarn (loc, OPT_Wc__23_extensions,
"%<auto(x)%> only available with "
"%<-std=c++2b%> or %<-std=gnu++2b%>");
diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast12.C b/gcc/testsuite/g++.dg/cpp23/auto-fncast12.C
new file mode 100644
index 00000000000..2856c2846fc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast12.C
@@ -0,0 +1,8 @@
+// PR c++/104752
+// { dg-do compile { target c++23 } }
+
+template<class T>
+concept C = true;
+auto x = auto(1); // valid (P0849R8)
+auto y = C auto(1); // { dg-error "cannot be constrained" }
+auto z = C auto{1}; // { dg-error "cannot be constrained" }
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