c++: placeholder type constraint inside range-for [PR99869]

Message ID 20210401200902.248304-1-ppalka@redhat.com
State New
Headers show
Series
  • c++: placeholder type constraint inside range-for [PR99869]
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Commit Message

Bill Schmidt via Gcc-patches April 1, 2021, 8:09 p.m.
In the testcase below, during ahead-of-time deduction of a constrained
auto from do_range_for_auto_deduction, we trip over the assert inside
do_auto_deduction that expects the deduction context to be
adc_return_type or adc_variable_type, but the context in this case is
adc_unspecified.

We could safely relax the assert to also accept adc_unspecified, but it
seems the context should really be adc_variable_type in this case.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

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.
---
 gcc/cp/parser.c                                    |  4 +++-
 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C | 10 ++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C

-- 
2.31.1.133.g84d06cdc06

Comments

Bill Schmidt via Gcc-patches April 1, 2021, 9:22 p.m. | #1
On 4/1/21 4:09 PM, Patrick Palka wrote:
> In the testcase below, during ahead-of-time deduction of a constrained

> auto from do_range_for_auto_deduction, we trip over the assert inside

> do_auto_deduction that expects the deduction context to be

> adc_return_type or adc_variable_type, but the context in this case is

> adc_unspecified.

> 

> We could safely relax the assert to also accept adc_unspecified, but it

> seems the context should really be adc_variable_type in this case.

> 

> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for

> trunk?


OK.

> 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.

> ---

>   gcc/cp/parser.c                                    |  4 +++-

>   gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C | 10 ++++++++++

>   2 files changed, 13 insertions(+), 1 deletion(-)

>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder6.C

> 

> 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..18e7b56d77f

> --- /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 : "") {}

> +}

>

Patch

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..18e7b56d77f
--- /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 : "") {}
+}