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c++: Lambda in friend of constrained class [PR94645]

Message ID 20200423200948.1949802-1-ppalka@redhat.com
State New
Headers show
Series c++: Lambda in friend of constrained class [PR94645] | expand

Commit Message

Patrick Palka April 23, 2020, 8:09 p.m. UTC
In the testcase below, when grokfndecl processes the operator() decl for the
lambda inside the friend function foo, processing_template_decl is rightly 1,
but template_class_depth on the lambda's closure type incorrectly returns 0
instead of 1.

Since processing_template_decl > template_class_depth, this makes grokfndecl
think that the operator() has its own set of template arguments, and so we
attach the innermost set of constraints -- those belonging to struct l -- to the
operator() decl.  We then get confused when checking constraints_satisfied_p on
the operator() because it doesn't have template information and yet has
constraints associated with it.

This patch fixes template_class_depth to return the correct template nesting
level in cases like these, so that when it hits a friend function it walks into
the DECL_FRIEND_CONTEXT of the friend rather than into the CP_DECL_CONTEXT.

Bootstrapped and regtested on x86_64-pc-linux-gnu, and also tested on cmcstl2,
range-v3, and fmt libraries.

gcc/cp/ChangeLog:

	PR c++/94645
	* pt.c (template_class_depth): Walk into the DECL_FRIEND_CONTEXT of a
	friend declaration rather than into its CP_DECL_CONTEXT.

gcc/testsuite/ChangeLog:

	PR c++/94645
	* g++.dg/cpp2a/concepts-lambda6.C: New test.
---
 gcc/cp/pt.c                                   |  7 ++++++-
 gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C

Comments

Jason Merrill April 23, 2020, 9:16 p.m. UTC | #1
On 4/23/20 4:09 PM, Patrick Palka wrote:
> In the testcase below, when grokfndecl processes the operator() decl for the
> lambda inside the friend function foo, processing_template_decl is rightly 1,
> but template_class_depth on the lambda's closure type incorrectly returns 0
> instead of 1.
> 
> Since processing_template_decl > template_class_depth, this makes grokfndecl
> think that the operator() has its own set of template arguments, and so we
> attach the innermost set of constraints -- those belonging to struct l -- to the
> operator() decl.  We then get confused when checking constraints_satisfied_p on
> the operator() because it doesn't have template information and yet has
> constraints associated with it.
> 
> This patch fixes template_class_depth to return the correct template nesting
> level in cases like these, so that when it hits a friend function it walks into
> the DECL_FRIEND_CONTEXT of the friend rather than into the CP_DECL_CONTEXT.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, and also tested on cmcstl2,
> range-v3, and fmt libraries.

OK.

> gcc/cp/ChangeLog:
> 
> 	PR c++/94645
> 	* pt.c (template_class_depth): Walk into the DECL_FRIEND_CONTEXT of a
> 	friend declaration rather than into its CP_DECL_CONTEXT.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/94645
> 	* g++.dg/cpp2a/concepts-lambda6.C: New test.
> ---
>   gcc/cp/pt.c                                   |  7 ++++++-
>   gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C | 19 +++++++++++++++++++
>   2 files changed, 25 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C
> 
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 0e3e7b2039a..08a35c41007 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -390,7 +390,12 @@ template_class_depth (tree type)
>   	++depth;
>   
>         if (DECL_P (type))
> -	type = CP_DECL_CONTEXT (type);
> +	{
> +	  if (tree fctx = DECL_FRIEND_CONTEXT (type))
> +	    type = fctx;
> +	  else
> +	    type = CP_DECL_CONTEXT (type);
> +	}
>         else if (LAMBDA_TYPE_P (type) && LAMBDA_TYPE_EXTRA_SCOPE (type))
>   	type = LAMBDA_TYPE_EXTRA_SCOPE (type);
>         else
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C
> new file mode 100644
> index 00000000000..244421e64ec
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C
> @@ -0,0 +1,19 @@
> +// PR c++/94632
> +// { dg-do compile { target concepts } }
> +
> +struct unordered_map {
> +  int cend() const noexcept;
> +};
> +
> +template <typename a> concept HasMapInterface = requires(a t) { t.cend(); };
> +
> +template <typename Mapper> requires HasMapInterface<decltype(Mapper::map())>
> +struct l {
> +  friend void foo(l opt) { ([]() {})(); }
> +};
> +
> +struct p {
> +  static unordered_map map();
> +};
> +
> +void g(l<p> *y) { foo(*y); }
>
diff mbox series

Patch

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0e3e7b2039a..08a35c41007 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -390,7 +390,12 @@  template_class_depth (tree type)
 	++depth;
 
       if (DECL_P (type))
-	type = CP_DECL_CONTEXT (type);
+	{
+	  if (tree fctx = DECL_FRIEND_CONTEXT (type))
+	    type = fctx;
+	  else
+	    type = CP_DECL_CONTEXT (type);
+	}
       else if (LAMBDA_TYPE_P (type) && LAMBDA_TYPE_EXTRA_SCOPE (type))
 	type = LAMBDA_TYPE_EXTRA_SCOPE (type);
       else
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C
new file mode 100644
index 00000000000..244421e64ec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C
@@ -0,0 +1,19 @@ 
+// PR c++/94632
+// { dg-do compile { target concepts } }
+
+struct unordered_map {
+  int cend() const noexcept;
+};
+
+template <typename a> concept HasMapInterface = requires(a t) { t.cend(); };
+
+template <typename Mapper> requires HasMapInterface<decltype(Mapper::map())>
+struct l {
+  friend void foo(l opt) { ([]() {})(); }
+};
+
+struct p {
+  static unordered_map map();
+};
+
+void g(l<p> *y) { foo(*y); }