| Message ID | 20220302183126.356040-1-polacek@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Don't allow type-constraint auto(x) [PR104752] | expand |
On 3/2/22 14:31, Marek Polacek wrote: > 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. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > 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. > --- > gcc/cp/semantics.cc | 1 + > gcc/cp/typeck2.cc | 1 + > gcc/testsuite/g++.dg/cpp23/auto-fncast12.C | 8 ++++++++ > 3 files changed, 10 insertions(+) > create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast12.C > > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc > index a2c0eb050e6..5129b12f00f 100644 > --- a/gcc/cp/semantics.cc > +++ b/gcc/cp/semantics.cc > @@ -3148,6 +3148,7 @@ finish_compound_literal (tree type, tree compound_literal, > /* C++23 auto{x}. */ > else if (is_auto (type) > && !AUTO_IS_DECLTYPE (type) > + && !is_constrained_auto (type) > && CONSTRUCTOR_NELTS (compound_literal) == 1) > { > if (cxx_dialect < cxx23) > diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc > index 39d03e4c3c4..c9314bbeb6f 100644 > --- a/gcc/cp/typeck2.cc > +++ b/gcc/cp/typeck2.cc > @@ -2305,6 +2305,7 @@ build_functional_cast_1 (location_t loc, tree exp, tree parms, > init = parms; > /* C++23 auto(x). */ > else if (!AUTO_IS_DECLTYPE (anode) > + && !is_constrained_auto (anode) > && list_length (parms) == 1) > { > init = TREE_VALUE (parms); We might get a better diagnostic by moving this test inside the block and saying that the auto can't be constrained, instead of "invalid use of auto"? > 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..f513f7c9325 > --- /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 "invalid use" } > +auto z = C auto{1}; // { dg-error "invalid use" } > > base-commit: 8977f4bec650bb6975792772245b07b722ee9843
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc index a2c0eb050e6..5129b12f00f 100644 --- a/gcc/cp/semantics.cc +++ b/gcc/cp/semantics.cc @@ -3148,6 +3148,7 @@ finish_compound_literal (tree type, tree compound_literal, /* C++23 auto{x}. */ else if (is_auto (type) && !AUTO_IS_DECLTYPE (type) + && !is_constrained_auto (type) && CONSTRUCTOR_NELTS (compound_literal) == 1) { if (cxx_dialect < cxx23) diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc index 39d03e4c3c4..c9314bbeb6f 100644 --- a/gcc/cp/typeck2.cc +++ b/gcc/cp/typeck2.cc @@ -2305,6 +2305,7 @@ build_functional_cast_1 (location_t loc, tree exp, tree parms, init = parms; /* C++23 auto(x). */ else if (!AUTO_IS_DECLTYPE (anode) + && !is_constrained_auto (anode) && list_length (parms) == 1) { init = TREE_VALUE (parms); 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..f513f7c9325 --- /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 "invalid use" } +auto z = C auto{1}; // { dg-error "invalid use" }
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. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? 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. --- gcc/cp/semantics.cc | 1 + gcc/cp/typeck2.cc | 1 + gcc/testsuite/g++.dg/cpp23/auto-fncast12.C | 8 ++++++++ 3 files changed, 10 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast12.C base-commit: 8977f4bec650bb6975792772245b07b722ee9843