[PATCH] c++: parenthesized -> resolving to static member [PR98283]

[Patrick Palka]

On Fri, 5 May 2023, Patrick Palka wrote:

> Here we're neglecting to propagate parenthesized-ness when the member
> access expression (this->m) resolves to a static member (and thus
> finish_class_member_access_expr yields a VAR_DECL instead of a
> COMPONENT_REF).
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does look OK for
> trunk?
> 
> 	PR c++/98283
> 
> gcc/cp/ChangeLog:
> 
> 	* pt.cc (tsubst_copy_and_build) <case COMPONENT_REF>: Use
> 	force_paren_expr on the result of finish_class_member_access_expr
> 	if REF_PARENTHESIZED_P.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp1y/paren6.C: New test.
> ---
>  gcc/cp/pt.cc                        |  4 ++--
>  gcc/cp/semantics.cc                 |  4 ++--
>  gcc/testsuite/g++.dg/cpp1y/paren6.C | 14 ++++++++++++++
>  3 files changed, 18 insertions(+), 4 deletions(-)
>  create mode 100644 gcc/testsuite/g++.dg/cpp1y/paren6.C
> 
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 5446b5058b7..9f5549e8f29 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -21502,8 +21502,8 @@ tsubst_copy_and_build (tree t,
>  	r = finish_class_member_access_expr (object, member,
>  					     /*template_p=*/false,
>  					     complain);
> -	if (TREE_CODE (r) == COMPONENT_REF)
> -	  REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (t);
> +	if (REF_PARENTHESIZED_P (t))
> +	  r = force_paren_expr (r);
>  	RETURN (r);
>        }
>  
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 474da71bff6..c4fea2f0f0f 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -2069,8 +2069,8 @@ finish_mem_initializers (tree mem_inits)
>     that the call to finish_decltype in do_auto_deduction will give the
>     right result.  If EVEN_UNEVAL, do this even in unevaluated context.  */
>  
> -tree
> -force_paren_expr (tree expr, bool even_uneval)
> +static tree
> +force_paren_expr (tree expr, bool even_uneval /* = false */)

Whoops, I managed to send the wrong amended patch (I opted to document
this default arg as a drive-by change after the fact).  The correct
patch is:

-- >8 --

Subject: [PATCH] c++: parenthesized -> resolving to static data member
 [PR98283]

Here we're neglecting to propagate parenthesized-ness when the
member access (this->m) resolves to a static data member (and
thus finish_class_member_access_expr yields a VAR_DECL instead
of a COMPONENT_REF).

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

	PR c++/98283

gcc/cp/ChangeLog:

	* pt.cc (tsubst_copy_and_build) <case COMPONENT_REF>: Use
	force_paren_expr on the result of finish_class_member_access_expr
	if REF_PARENTHESIZED_P.
	* semantics.cc (force_paren_expr): Document default argument.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/paren6.C: New test.
---
 gcc/cp/pt.cc                        |  4 ++--
 gcc/cp/semantics.cc                 |  2 +-
 gcc/testsuite/g++.dg/cpp1y/paren6.C | 14 ++++++++++++++
 3 files changed, 17 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/paren6.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 5446b5058b7..9f5549e8f29 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21502,8 +21502,8 @@ tsubst_copy_and_build (tree t,
 	r = finish_class_member_access_expr (object, member,
 					     /*template_p=*/false,
 					     complain);
-	if (TREE_CODE (r) == COMPONENT_REF)
-	  REF_PARENTHESIZED_P (r) = REF_PARENTHESIZED_P (t);
+	if (REF_PARENTHESIZED_P (t))
+	  r = force_paren_expr (r);
 	RETURN (r);
       }
 
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 474da71bff6..13c6582b628 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -2070,7 +2070,7 @@ finish_mem_initializers (tree mem_inits)
    right result.  If EVEN_UNEVAL, do this even in unevaluated context.  */
 
 tree
-force_paren_expr (tree expr, bool even_uneval)
+force_paren_expr (tree expr, bool even_uneval /* = false */)
 {
   /* This is only needed for decltype(auto) in C++14.  */
   if (cxx_dialect < cxx14)
diff --git a/gcc/testsuite/g++.dg/cpp1y/paren6.C b/gcc/testsuite/g++.dg/cpp1y/paren6.C
new file mode 100644
index 00000000000..812a99ca91c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/paren6.C
@@ -0,0 +1,14 @@
+// PR c++/98283
+// { dg-do compile { target c++14 } }
+
+struct A {
+  static int m;
+};
+
+template<class T>
+struct B : T {
+  decltype(auto) f() { return (this->m);  }
+};
+
+using type = decltype(B<A>().f());
+using type = int&;
-- 
2.40.1.476.g69c786637d