[PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

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

-- >8 --

r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
first so that we prefer processing a local specialization in an evaluated
context even if its first use is in an unevaluated context.  But this
means we need to avoid walking a tree that already has extra args/specs
saved because the list of saved specs appears to be an evaluated
context.  It seems then that we should be calculating the saved specs
from scratch each time, rather than potentially walking the saved specs
list from an earlier partial instantiation when calling build_extra_args
a second time around.

	PR c++/114303

gcc/cp/ChangeLog:

	* constraint.cc (tsubst_requires_expr): Clear
	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
	on the new IF_STMT instead of t which might already have
	IF_STMT_EXTRA_ARGS.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
---
 gcc/cp/constraint.cc                             |  1 +
 gcc/cp/pt.cc                                     |  2 +-
 .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 49de3211d4c..8a3b5d80ba7 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
 	 matching or dguide constraint rewriting), in which case we need
 	 to partially substitute.  */
       t = copy_node (t);
+      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
       REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
       return t;
     }
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8cf0d5b7a8d..37f2392d035 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	  IF_COND (stmt) = IF_COND (t);
 	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
 	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
-	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
+	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
 	  add_stmt (stmt);
 	  break;
 	}
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
new file mode 100644
index 00000000000..038c2a41210
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
@@ -0,0 +1,16 @@
+// PR c++/114303
+// { dg-do compile { target c++17 } }
+
+struct A { static constexpr bool value = true; };
+
+int main() {
+  [](auto x1) {
+    return [&](auto) {
+      return [&](auto x3) {
+        if constexpr (decltype(x3)::value) {
+          static_assert(decltype(x1)::value);
+        }
+      }(A{});
+    }(0);
+  }(A{});
+}
-- 
2.44.0.165.ge09f1254c5

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Jason Merrill]

On 3/11/24 12:53, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> OK for trunk and release branches?
> 
> -- >8 --
> 
> r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> first so that we prefer processing a local specialization in an evaluated
> context even if its first use is in an unevaluated context.  But this
> means we need to avoid walking a tree that already has extra args/specs
> saved because the list of saved specs appears to be an evaluated
> context.  It seems then that we should be calculating the saved specs
> from scratch each time, rather than potentially walking the saved specs
> list from an earlier partial instantiation when calling build_extra_args
> a second time around.

Makes sense, but I wonder if we want to approach that by avoiding 
walking into *_EXTRA_ARGS in extract_locals_r?  Or do we still want to 
walk into any nested extra args?  And if so, will we run into this same 
problem then?

> 	PR c++/114303
> 
> gcc/cp/ChangeLog:
> 
> 	* constraint.cc (tsubst_requires_expr): Clear
> 	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
> 	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
> 	on the new IF_STMT instead of t which might already have
> 	IF_STMT_EXTRA_ARGS.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
> ---
>   gcc/cp/constraint.cc                             |  1 +
>   gcc/cp/pt.cc                                     |  2 +-
>   .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
>   3 files changed, 18 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 49de3211d4c..8a3b5d80ba7 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
>   	 matching or dguide constraint rewriting), in which case we need
>   	 to partially substitute.  */
>         t = copy_node (t);
> +      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
>         REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
>         return t;
>       }
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 8cf0d5b7a8d..37f2392d035 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	  IF_COND (stmt) = IF_COND (t);
>   	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
>   	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> +	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
>   	  add_stmt (stmt);
>   	  break;
>   	}
> diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> new file mode 100644
> index 00000000000..038c2a41210
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> @@ -0,0 +1,16 @@
> +// PR c++/114303
> +// { dg-do compile { target c++17 } }
> +
> +struct A { static constexpr bool value = true; };
> +
> +int main() {
> +  [](auto x1) {
> +    return [&](auto) {
> +      return [&](auto x3) {
> +        if constexpr (decltype(x3)::value) {
> +          static_assert(decltype(x1)::value);
> +        }
> +      }(A{});
> +    }(0);
> +  }(A{});
> +}

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Tue, 12 Mar 2024, Jason Merrill wrote:

> On 3/11/24 12:53, Patrick Palka wrote:
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > OK for trunk and release branches?
> > 
> > -- >8 --
> > 
> > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> > first so that we prefer processing a local specialization in an evaluated
> > context even if its first use is in an unevaluated context.  But this
> > means we need to avoid walking a tree that already has extra args/specs
> > saved because the list of saved specs appears to be an evaluated
> > context.  It seems then that we should be calculating the saved specs
> > from scratch each time, rather than potentially walking the saved specs
> > list from an earlier partial instantiation when calling build_extra_args
> > a second time around.
> 
> Makes sense, but I wonder if we want to approach that by avoiding walking into
> *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into any nested
> extra args?  And if so, will we run into this same problem then?

I'm not sure totally but I'd expect a nested extra-args tree to always
have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
any substitution before the inner extra-args tree can see it?

> 
> > 	PR c++/114303
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* constraint.cc (tsubst_requires_expr): Clear
> > 	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
> > 	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
> > 	on the new IF_STMT instead of t which might already have
> > 	IF_STMT_EXTRA_ARGS.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
> > ---
> >   gcc/cp/constraint.cc                             |  1 +
> >   gcc/cp/pt.cc                                     |  2 +-
> >   .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
> >   3 files changed, 18 insertions(+), 1 deletion(-)
> >   create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > 
> > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > index 49de3211d4c..8a3b5d80ba7 100644
> > --- a/gcc/cp/constraint.cc
> > +++ b/gcc/cp/constraint.cc
> > @@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info
> > info)
> >   	 matching or dguide constraint rewriting), in which case we need
> >   	 to partially substitute.  */
> >         t = copy_node (t);
> > +      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
> >         REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args,
> > info.complain);
> >         return t;
> >       }
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 8cf0d5b7a8d..37f2392d035 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> >   	  IF_COND (stmt) = IF_COND (t);
> >   	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
> >   	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> > -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> > +	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
> >   	  add_stmt (stmt);
> >   	  break;
> >   	}
> > diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > new file mode 100644
> > index 00000000000..038c2a41210
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > @@ -0,0 +1,16 @@
> > +// PR c++/114303
> > +// { dg-do compile { target c++17 } }
> > +
> > +struct A { static constexpr bool value = true; };
> > +
> > +int main() {
> > +  [](auto x1) {
> > +    return [&](auto) {
> > +      return [&](auto x3) {
> > +        if constexpr (decltype(x3)::value) {
> > +          static_assert(decltype(x1)::value);
> > +        }
> > +      }(A{});
> > +    }(0);
> > +  }(A{});
> > +}
> 
> 

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Tue, 12 Mar 2024, Patrick Palka wrote:

> On Tue, 12 Mar 2024, Jason Merrill wrote:
> 
> > On 3/11/24 12:53, Patrick Palka wrote:
> > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > > OK for trunk and release branches?
> > > 
> > > -- >8 --
> > > 
> > > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> > > first so that we prefer processing a local specialization in an evaluated
> > > context even if its first use is in an unevaluated context.  But this
> > > means we need to avoid walking a tree that already has extra args/specs
> > > saved because the list of saved specs appears to be an evaluated
> > > context.  It seems then that we should be calculating the saved specs
> > > from scratch each time, rather than potentially walking the saved specs
> > > list from an earlier partial instantiation when calling build_extra_args
> > > a second time around.
> > 
> > Makes sense, but I wonder if we want to approach that by avoiding walking into
> > *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into any nested
> > extra args?  And if so, will we run into this same problem then?
> 
> I'm not sure totally but I'd expect a nested extra-args tree to always
> have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
> any substitution before the inner extra-args tree can see it?

... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
empty, and not have to explicitly avoid walking it.

> 
> > 
> > > 	PR c++/114303
> > > 
> > > gcc/cp/ChangeLog:
> > > 
> > > 	* constraint.cc (tsubst_requires_expr): Clear
> > > 	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
> > > 	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
> > > 	on the new IF_STMT instead of t which might already have
> > > 	IF_STMT_EXTRA_ARGS.
> > > 
> > > gcc/testsuite/ChangeLog:
> > > 
> > > 	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
> > > ---
> > >   gcc/cp/constraint.cc                             |  1 +
> > >   gcc/cp/pt.cc                                     |  2 +-
> > >   .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
> > >   3 files changed, 18 insertions(+), 1 deletion(-)
> > >   create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > > 
> > > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > > index 49de3211d4c..8a3b5d80ba7 100644
> > > --- a/gcc/cp/constraint.cc
> > > +++ b/gcc/cp/constraint.cc
> > > @@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info
> > > info)
> > >   	 matching or dguide constraint rewriting), in which case we need
> > >   	 to partially substitute.  */
> > >         t = copy_node (t);
> > > +      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
> > >         REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args,
> > > info.complain);
> > >         return t;
> > >       }
> > > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > > index 8cf0d5b7a8d..37f2392d035 100644
> > > --- a/gcc/cp/pt.cc
> > > +++ b/gcc/cp/pt.cc
> > > @@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
> > > complain, tree in_decl)
> > >   	  IF_COND (stmt) = IF_COND (t);
> > >   	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
> > >   	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> > > -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> > > +	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
> > >   	  add_stmt (stmt);
> > >   	  break;
> > >   	}
> > > diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > > b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > > new file mode 100644
> > > index 00000000000..038c2a41210
> > > --- /dev/null
> > > +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > > @@ -0,0 +1,16 @@
> > > +// PR c++/114303
> > > +// { dg-do compile { target c++17 } }
> > > +
> > > +struct A { static constexpr bool value = true; };
> > > +
> > > +int main() {
> > > +  [](auto x1) {
> > > +    return [&](auto) {
> > > +      return [&](auto x3) {
> > > +        if constexpr (decltype(x3)::value) {
> > > +          static_assert(decltype(x1)::value);
> > > +        }
> > > +      }(A{});
> > > +    }(0);
> > > +  }(A{});
> > > +}
> > 
> > 
> 

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Mon, 11 Mar 2024, Patrick Palka wrote:

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

Ping.

> 
> -- >8 --
> 
> r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> first so that we prefer processing a local specialization in an evaluated
> context even if its first use is in an unevaluated context.  But this
> means we need to avoid walking a tree that already has extra args/specs
> saved because the list of saved specs appears to be an evaluated
> context.  It seems then that we should be calculating the saved specs
> from scratch each time, rather than potentially walking the saved specs
> list from an earlier partial instantiation when calling build_extra_args
> a second time around.
> 
> 	PR c++/114303
> 
> gcc/cp/ChangeLog:
> 
> 	* constraint.cc (tsubst_requires_expr): Clear
> 	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
> 	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
> 	on the new IF_STMT instead of t which might already have
> 	IF_STMT_EXTRA_ARGS.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
> ---
>  gcc/cp/constraint.cc                             |  1 +
>  gcc/cp/pt.cc                                     |  2 +-
>  .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
>  3 files changed, 18 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 49de3211d4c..8a3b5d80ba7 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
>  	 matching or dguide constraint rewriting), in which case we need
>  	 to partially substitute.  */
>        t = copy_node (t);
> +      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
>        REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
>        return t;
>      }
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 8cf0d5b7a8d..37f2392d035 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>  	  IF_COND (stmt) = IF_COND (t);
>  	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
>  	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> +	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
>  	  add_stmt (stmt);
>  	  break;
>  	}
> diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> new file mode 100644
> index 00000000000..038c2a41210
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> @@ -0,0 +1,16 @@
> +// PR c++/114303
> +// { dg-do compile { target c++17 } }
> +
> +struct A { static constexpr bool value = true; };
> +
> +int main() {
> +  [](auto x1) {
> +    return [&](auto) {
> +      return [&](auto x3) {
> +        if constexpr (decltype(x3)::value) {
> +          static_assert(decltype(x1)::value);
> +        }
> +      }(A{});
> +    }(0);
> +  }(A{});
> +}
> -- 
> 2.44.0.165.ge09f1254c5
> 
> 

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Tue, 26 Mar 2024, Patrick Palka wrote:

> On Mon, 11 Mar 2024, Patrick Palka wrote:
> 
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
> > OK for trunk and release branches?
> 
> Ping.

Ping.

> 
> > 
> > -- >8 --
> > 
> > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> > first so that we prefer processing a local specialization in an evaluated
> > context even if its first use is in an unevaluated context.  But this
> > means we need to avoid walking a tree that already has extra args/specs
> > saved because the list of saved specs appears to be an evaluated
> > context.  It seems then that we should be calculating the saved specs
> > from scratch each time, rather than potentially walking the saved specs
> > list from an earlier partial instantiation when calling build_extra_args
> > a second time around.
> > 
> > 	PR c++/114303
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* constraint.cc (tsubst_requires_expr): Clear
> > 	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
> > 	* pt.cc (tsubst_stmt) <case IF_STMT>: Call build_extra_args
> > 	on the new IF_STMT instead of t which might already have
> > 	IF_STMT_EXTRA_ARGS.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
> > ---
> >  gcc/cp/constraint.cc                             |  1 +
> >  gcc/cp/pt.cc                                     |  2 +-
> >  .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
> >  3 files changed, 18 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > 
> > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > index 49de3211d4c..8a3b5d80ba7 100644
> > --- a/gcc/cp/constraint.cc
> > +++ b/gcc/cp/constraint.cc
> > @@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
> >  	 matching or dguide constraint rewriting), in which case we need
> >  	 to partially substitute.  */
> >        t = copy_node (t);
> > +      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
> >        REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
> >        return t;
> >      }
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 8cf0d5b7a8d..37f2392d035 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -18718,7 +18718,7 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> >  	  IF_COND (stmt) = IF_COND (t);
> >  	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
> >  	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> > -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> > +	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
> >  	  add_stmt (stmt);
> >  	  break;
> >  	}
> > diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > new file mode 100644
> > index 00000000000..038c2a41210
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
> > @@ -0,0 +1,16 @@
> > +// PR c++/114303
> > +// { dg-do compile { target c++17 } }
> > +
> > +struct A { static constexpr bool value = true; };
> > +
> > +int main() {
> > +  [](auto x1) {
> > +    return [&](auto) {
> > +      return [&](auto x3) {
> > +        if constexpr (decltype(x3)::value) {
> > +          static_assert(decltype(x1)::value);
> > +        }
> > +      }(A{});
> > +    }(0);
> > +  }(A{});
> > +}
> > -- 
> > 2.44.0.165.ge09f1254c5
> > 
> > 
> 

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Jason Merrill]

On 3/12/24 10:51, Patrick Palka wrote:
> On Tue, 12 Mar 2024, Patrick Palka wrote:
>> On Tue, 12 Mar 2024, Jason Merrill wrote:
>>> On 3/11/24 12:53, Patrick Palka wrote:
>>>>
>>>> r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
>>>> first so that we prefer processing a local specialization in an evaluated
>>>> context even if its first use is in an unevaluated context.  But this
>>>> means we need to avoid walking a tree that already has extra args/specs
>>>> saved because the list of saved specs appears to be an evaluated
>>>> context.  It seems then that we should be calculating the saved specs
>>>> from scratch each time, rather than potentially walking the saved specs
>>>> list from an earlier partial instantiation when calling build_extra_args
>>>> a second time around.
>>>
>>> Makes sense, but I wonder if we want to approach that by avoiding walking into
>>> *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into any nested
>>> extra args?  And if so, will we run into this same problem then?
>>
>> I'm not sure totally but I'd expect a nested extra-args tree to always
>> have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
>> any substitution before the inner extra-args tree can see it?
> 
> ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
> empty, and not have to explicitly avoid walking it.

It seems more robust to me to handle _EXTRA_ARGS appropriately in 
build_extra_args rather than expect callers to know that they shouldn't 
pass in a tree with _EXTRA_ARGS set.  At least check and abort in that case?

Jason

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Wed, 10 Apr 2024, Jason Merrill wrote:

> On 3/12/24 10:51, Patrick Palka wrote:
> > On Tue, 12 Mar 2024, Patrick Palka wrote:
> > > On Tue, 12 Mar 2024, Jason Merrill wrote:
> > > > On 3/11/24 12:53, Patrick Palka wrote:
> > > > > 
> > > > > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> > > > > first so that we prefer processing a local specialization in an
> > > > > evaluated
> > > > > context even if its first use is in an unevaluated context.  But this
> > > > > means we need to avoid walking a tree that already has extra
> > > > > args/specs
> > > > > saved because the list of saved specs appears to be an evaluated
> > > > > context.  It seems then that we should be calculating the saved specs
> > > > > from scratch each time, rather than potentially walking the saved
> > > > > specs
> > > > > list from an earlier partial instantiation when calling
> > > > > build_extra_args
> > > > > a second time around.
> > > > 
> > > > Makes sense, but I wonder if we want to approach that by avoiding
> > > > walking into
> > > > *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into any
> > > > nested
> > > > extra args?  And if so, will we run into this same problem then?
> > > 
> > > I'm not sure totally but I'd expect a nested extra-args tree to always
> > > have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
> > > any substitution before the inner extra-args tree can see it?
> > 
> > ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
> > empty, and not have to explicitly avoid walking it.
> 
> It seems more robust to me to handle _EXTRA_ARGS appropriately in
> build_extra_args rather than expect callers to know that they shouldn't pass
> in a tree with _EXTRA_ARGS set.  At least check and abort in that case?

Sounds good.  That IMHO seems simpler than actually avoiding walking
into *_EXTRA_ARGS from extract_locals_r because we'd have to repeat
the walking logic from cp_walk_subtree modulo the *_EXTRA_ARGS walk.

How does the following look? Bootstraped and regtested on
x86_64-pc-linux-gnu.

-- > 8--

Subject: [PATCH] c++: build_extra_args recapturing local specs [PR114303]

	PR c++/114303

gcc/cp/ChangeLog:

	* constraint.cc (tsubst_requires_expr): Clear
	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
	* pt.cc (extract_locals_r): Assert *_EXTRA_ARGS is empty.
	(tsubst_stmt) <case IF_STMT>: Call build_extra_args
	on the new IF_STMT instead of t which might already have
	IF_STMT_EXTRA_ARGS.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
---
 gcc/cp/constraint.cc                             |  1 +
 gcc/cp/pt.cc                                     | 16 +++++++++++++++-
 .../g++.dg/cpp1z/constexpr-if-lambda6.C          | 16 ++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 49de3211d4c..8a3b5d80ba7 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
 	 matching or dguide constraint rewriting), in which case we need
 	 to partially substitute.  */
       t = copy_node (t);
+      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
       REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
       return t;
     }
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c38594cd862..6cc9b95fc06 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -13310,6 +13310,19 @@ extract_locals_r (tree *tp, int *walk_subtrees, void *data_)
     /* Remember local typedefs (85214).  */
     tp = &TYPE_NAME (*tp);
 
+  if (has_extra_args_mechanism_p (*tp))
+    {
+      if (PACK_EXPANSION_P (*tp))
+	gcc_checking_assert (!PACK_EXPANSION_EXTRA_ARGS (*tp));
+      else if (TREE_CODE (*tp) == REQUIRES_EXPR)
+	gcc_checking_assert (!REQUIRES_EXPR_EXTRA_ARGS (*tp));
+      else if (TREE_CODE (*tp) == IF_STMT
+	       && IF_STMT_CONSTEXPR_P (*tp))
+	gcc_checking_assert (!IF_STMT_EXTRA_ARGS (*tp));
+      else
+	gcc_unreachable ();
+    }
+
   if (TREE_CODE (*tp) == DECL_EXPR)
     {
       tree decl = DECL_EXPR_DECL (*tp);
@@ -18738,7 +18751,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	  IF_COND (stmt) = IF_COND (t);
 	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
 	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
-	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
+	  IF_SCOPE (stmt) = NULL_TREE;
+	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
 	  add_stmt (stmt);
 	  break;
 	}
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
new file mode 100644
index 00000000000..038c2a41210
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
@@ -0,0 +1,16 @@
+// PR c++/114303
+// { dg-do compile { target c++17 } }
+
+struct A { static constexpr bool value = true; };
+
+int main() {
+  [](auto x1) {
+    return [&](auto) {
+      return [&](auto x3) {
+        if constexpr (decltype(x3)::value) {
+          static_assert(decltype(x1)::value);
+        }
+      }(A{});
+    }(0);
+  }(A{});
+}
-- 
2.44.0.548.g91ec36f2cc

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Jason Merrill]

On 4/10/24 17:39, Patrick Palka wrote:
> On Wed, 10 Apr 2024, Jason Merrill wrote:
> 
>> On 3/12/24 10:51, Patrick Palka wrote:
>>> On Tue, 12 Mar 2024, Patrick Palka wrote:
>>>> On Tue, 12 Mar 2024, Jason Merrill wrote:
>>>>> On 3/11/24 12:53, Patrick Palka wrote:
>>>>>>
>>>>>> r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
>>>>>> first so that we prefer processing a local specialization in an
>>>>>> evaluated
>>>>>> context even if its first use is in an unevaluated context.  But this
>>>>>> means we need to avoid walking a tree that already has extra
>>>>>> args/specs
>>>>>> saved because the list of saved specs appears to be an evaluated
>>>>>> context.  It seems then that we should be calculating the saved specs
>>>>>> from scratch each time, rather than potentially walking the saved
>>>>>> specs
>>>>>> list from an earlier partial instantiation when calling
>>>>>> build_extra_args
>>>>>> a second time around.
>>>>>
>>>>> Makes sense, but I wonder if we want to approach that by avoiding
>>>>> walking into
>>>>> *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into any
>>>>> nested
>>>>> extra args?  And if so, will we run into this same problem then?
>>>>
>>>> I'm not sure totally but I'd expect a nested extra-args tree to always
>>>> have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
>>>> any substitution before the inner extra-args tree can see it?
>>>
>>> ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
>>> empty, and not have to explicitly avoid walking it.
>>
>> It seems more robust to me to handle _EXTRA_ARGS appropriately in
>> build_extra_args rather than expect callers to know that they shouldn't pass
>> in a tree with _EXTRA_ARGS set.  At least check and abort in that case?
> 
> Sounds good.  That IMHO seems simpler than actually avoiding walking
> into *_EXTRA_ARGS from extract_locals_r because we'd have to repeat
> the walking logic from cp_walk_subtree modulo the *_EXTRA_ARGS walk.
> 
> How does the following look? Bootstraped and regtested on
> x86_64-pc-linux-gnu.
> 
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index c38594cd862..6cc9b95fc06 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -13310,6 +13310,19 @@ extract_locals_r (tree *tp, int *walk_subtrees, void *data_)
>       /* Remember local typedefs (85214).  */
>       tp = &TYPE_NAME (*tp);
>   

Please add a comment explaining why it needs to be null.

Also, how about a generic _EXTRA_ARGS accessor so places like this don't 
need to check each code themselves?

> +  if (has_extra_args_mechanism_p (*tp))
> +    {
> +      if (PACK_EXPANSION_P (*tp))
> +	gcc_checking_assert (!PACK_EXPANSION_EXTRA_ARGS (*tp));
> +      else if (TREE_CODE (*tp) == REQUIRES_EXPR)
> +	gcc_checking_assert (!REQUIRES_EXPR_EXTRA_ARGS (*tp));
> +      else if (TREE_CODE (*tp) == IF_STMT
> +	       && IF_STMT_CONSTEXPR_P (*tp))
> +	gcc_checking_assert (!IF_STMT_EXTRA_ARGS (*tp));
> +      else
> +	gcc_unreachable ();
> +    }
> +
>     if (TREE_CODE (*tp) == DECL_EXPR)
>       {
>         tree decl = DECL_EXPR_DECL (*tp);
> @@ -18738,7 +18751,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
>   	  IF_COND (stmt) = IF_COND (t);
>   	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
>   	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> +	  IF_SCOPE (stmt) = NULL_TREE;

What does IF_SCOPE have to do with this?

Jason

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Patrick Palka]

On Wed, 10 Apr 2024, Jason Merrill wrote:

> On 4/10/24 17:39, Patrick Palka wrote:
> > On Wed, 10 Apr 2024, Jason Merrill wrote:
> > 
> > > On 3/12/24 10:51, Patrick Palka wrote:
> > > > On Tue, 12 Mar 2024, Patrick Palka wrote:
> > > > > On Tue, 12 Mar 2024, Jason Merrill wrote:
> > > > > > On 3/11/24 12:53, Patrick Palka wrote:
> > > > > > > 
> > > > > > > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated
> > > > > > > contexts
> > > > > > > first so that we prefer processing a local specialization in an
> > > > > > > evaluated
> > > > > > > context even if its first use is in an unevaluated context.  But
> > > > > > > this
> > > > > > > means we need to avoid walking a tree that already has extra
> > > > > > > args/specs
> > > > > > > saved because the list of saved specs appears to be an evaluated
> > > > > > > context.  It seems then that we should be calculating the saved
> > > > > > > specs
> > > > > > > from scratch each time, rather than potentially walking the saved
> > > > > > > specs
> > > > > > > list from an earlier partial instantiation when calling
> > > > > > > build_extra_args
> > > > > > > a second time around.
> > > > > > 
> > > > > > Makes sense, but I wonder if we want to approach that by avoiding
> > > > > > walking into
> > > > > > *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into
> > > > > > any
> > > > > > nested
> > > > > > extra args?  And if so, will we run into this same problem then?
> > > > > 
> > > > > I'm not sure totally but I'd expect a nested extra-args tree to always
> > > > > have empty *_EXTRA_ARGS since the outer extra-args tree should
> > > > > intercept
> > > > > any substitution before the inner extra-args tree can see it?
> > > > 
> > > > ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
> > > > empty, and not have to explicitly avoid walking it.
> > > 
> > > It seems more robust to me to handle _EXTRA_ARGS appropriately in
> > > build_extra_args rather than expect callers to know that they shouldn't
> > > pass
> > > in a tree with _EXTRA_ARGS set.  At least check and abort in that case?
> > 
> > Sounds good.  That IMHO seems simpler than actually avoiding walking
> > into *_EXTRA_ARGS from extract_locals_r because we'd have to repeat
> > the walking logic from cp_walk_subtree modulo the *_EXTRA_ARGS walk.
> > 
> > How does the following look? Bootstraped and regtested on
> > x86_64-pc-linux-gnu.
> > 
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index c38594cd862..6cc9b95fc06 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -13310,6 +13310,19 @@ extract_locals_r (tree *tp, int *walk_subtrees,
> > void *data_)
> >       /* Remember local typedefs (85214).  */
> >       tp = &TYPE_NAME (*tp);
> >   
> 
> Please add a comment explaining why it needs to be null.
> 
> Also, how about a generic _EXTRA_ARGS accessor so places like this don't need
> to check each code themselves?

Sounds good.

> 
> > +  if (has_extra_args_mechanism_p (*tp))
> > +    {
> > +      if (PACK_EXPANSION_P (*tp))
> > +	gcc_checking_assert (!PACK_EXPANSION_EXTRA_ARGS (*tp));
> > +      else if (TREE_CODE (*tp) == REQUIRES_EXPR)
> > +	gcc_checking_assert (!REQUIRES_EXPR_EXTRA_ARGS (*tp));
> > +      else if (TREE_CODE (*tp) == IF_STMT
> > +	       && IF_STMT_CONSTEXPR_P (*tp))
> > +	gcc_checking_assert (!IF_STMT_EXTRA_ARGS (*tp));
> > +      else
> > +	gcc_unreachable ();
> > +    }
> > +
> >     if (TREE_CODE (*tp) == DECL_EXPR)
> >       {
> >         tree decl = DECL_EXPR_DECL (*tp);
> > @@ -18738,7 +18751,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> >   	  IF_COND (stmt) = IF_COND (t);
> >   	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
> >   	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
> > -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
> > +	  IF_SCOPE (stmt) = NULL_TREE;
> 
> What does IF_SCOPE have to do with this?

IF_SCOPE is the same field as IF_STMT_EXTRA_ARGS so we need to clear it
before calling build_extra_args to avoid tripping over the added assert.

How does the following look?

-- >8 --

Subject: [PATCH] c++: build_extra_args recapturing local specs [PR114303]

	PR c++/114303

gcc/cp/ChangeLog:

	* constraint.cc (tsubst_requires_expr): Clear
	REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
	* pt.cc (tree_extra_args): Define.
	(extract_locals_r): Assert *_EXTRA_ARGS is empty.
	(tsubst_stmt) <case IF_STMT>: Clear IF_SCOPE on the new
	IF_STMT.  Call build_extra_args on the new IF_STMT instead
	of t which might already have IF_STMT_EXTRA_ARGS.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
---
 gcc/cp/constraint.cc                          |  1 +
 gcc/cp/pt.cc                                  | 31 ++++++++++++++++++-
 .../g++.dg/cpp1z/constexpr-if-lambda6.C       | 16 ++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 49de3211d4c..8a3b5d80ba7 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
 	 matching or dguide constraint rewriting), in which case we need
 	 to partially substitute.  */
       t = copy_node (t);
+      REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
       REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
       return t;
     }
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c999e2d9baa..1b17784f6b5 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -3859,6 +3859,25 @@ has_extra_args_mechanism_p (const_tree t)
 	  || TREE_CODE (t) == LAMBDA_EXPR); /* LAMBDA_EXPR_EXTRA_ARGS  */
 }
 
+/* Return *_EXTRA_ARGS of the given supported tree T.  */
+
+static tree&
+tree_extra_args (tree t)
+{
+  gcc_checking_assert (has_extra_args_mechanism_p (t));
+
+  if (PACK_EXPANSION_P (t))
+    return PACK_EXPANSION_EXTRA_ARGS (t);
+  else if (TREE_CODE (t) == REQUIRES_EXPR)
+    return REQUIRES_EXPR_EXTRA_ARGS (t);
+  else if (TREE_CODE (t) == IF_STMT
+	   && IF_STMT_CONSTEXPR_P (t))
+    return IF_STMT_EXTRA_ARGS (t);
+  else if (TREE_CODE (t) == LAMBDA_EXPR)
+    return LAMBDA_EXPR_EXTRA_ARGS (t);
+  gcc_unreachable ();
+}
+
 /* Structure used to track the progress of find_parameter_packs_r.  */
 struct find_parameter_pack_data
 {
@@ -13292,6 +13311,15 @@ extract_locals_r (tree *tp, int *walk_subtrees, void *data_)
     /* Remember local typedefs (85214).  */
     tp = &TYPE_NAME (*tp);
 
+  if (has_extra_args_mechanism_p (*tp))
+    /* We don't want to walk *_EXTRA_ARGS to avoid seeing a captured
+       local in an evaluated context that's otherwise used only in an
+       unevaluated context (PR114303).  So callers should ensure the
+       *_EXTRA_ARGS of the outermost tree is empty.  (Nested *_EXTRA_ARGS
+       should naturally be empty since the outermost (extra-args) tree
+       will intercept any substitution.)  */
+    gcc_checking_assert (!tree_extra_args (*tp));
+
   if (TREE_CODE (*tp) == DECL_EXPR)
     {
       tree decl = DECL_EXPR_DECL (*tp);
@@ -18720,7 +18748,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	  IF_COND (stmt) = IF_COND (t);
 	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
 	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
-	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
+	  IF_SCOPE (stmt) = NULL_TREE;
+	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
 	  add_stmt (stmt);
 	  break;
 	}
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
new file mode 100644
index 00000000000..038c2a41210
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
@@ -0,0 +1,16 @@
+// PR c++/114303
+// { dg-do compile { target c++17 } }
+
+struct A { static constexpr bool value = true; };
+
+int main() {
+  [](auto x1) {
+    return [&](auto) {
+      return [&](auto x3) {
+        if constexpr (decltype(x3)::value) {
+          static_assert(decltype(x1)::value);
+        }
+      }(A{});
+    }(0);
+  }(A{});
+}
-- 
2.44.0.568.g436d4e5b14

Re: [PATCH] c++: recalculating local specs via build_extra_args [PR114303]

[Jason Merrill]

On 4/10/24 20:00, Patrick Palka wrote:
> On Wed, 10 Apr 2024, Jason Merrill wrote:
> 
>> On 4/10/24 17:39, Patrick Palka wrote:
>>> On Wed, 10 Apr 2024, Jason Merrill wrote:
>>>
>>>> On 3/12/24 10:51, Patrick Palka wrote:
>>>>> On Tue, 12 Mar 2024, Patrick Palka wrote:
>>>>>> On Tue, 12 Mar 2024, Jason Merrill wrote:
>>>>>>> On 3/11/24 12:53, Patrick Palka wrote:
>>>>>>>>
>>>>>>>> r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated
>>>>>>>> contexts
>>>>>>>> first so that we prefer processing a local specialization in an
>>>>>>>> evaluated
>>>>>>>> context even if its first use is in an unevaluated context.  But
>>>>>>>> this
>>>>>>>> means we need to avoid walking a tree that already has extra
>>>>>>>> args/specs
>>>>>>>> saved because the list of saved specs appears to be an evaluated
>>>>>>>> context.  It seems then that we should be calculating the saved
>>>>>>>> specs
>>>>>>>> from scratch each time, rather than potentially walking the saved
>>>>>>>> specs
>>>>>>>> list from an earlier partial instantiation when calling
>>>>>>>> build_extra_args
>>>>>>>> a second time around.
>>>>>>>
>>>>>>> Makes sense, but I wonder if we want to approach that by avoiding
>>>>>>> walking into
>>>>>>> *_EXTRA_ARGS in extract_locals_r?  Or do we still want to walk into
>>>>>>> any
>>>>>>> nested
>>>>>>> extra args?  And if so, will we run into this same problem then?
>>>>>>
>>>>>> I'm not sure totally but I'd expect a nested extra-args tree to always
>>>>>> have empty *_EXTRA_ARGS since the outer extra-args tree should
>>>>>> intercept
>>>>>> any substitution before the inner extra-args tree can see it?
>>>>>
>>>>> ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
>>>>> empty, and not have to explicitly avoid walking it.
>>>>
>>>> It seems more robust to me to handle _EXTRA_ARGS appropriately in
>>>> build_extra_args rather than expect callers to know that they shouldn't
>>>> pass
>>>> in a tree with _EXTRA_ARGS set.  At least check and abort in that case?
>>>
>>> Sounds good.  That IMHO seems simpler than actually avoiding walking
>>> into *_EXTRA_ARGS from extract_locals_r because we'd have to repeat
>>> the walking logic from cp_walk_subtree modulo the *_EXTRA_ARGS walk.
>>>
>>> How does the following look? Bootstraped and regtested on
>>> x86_64-pc-linux-gnu.
>>>
>>> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
>>> index c38594cd862..6cc9b95fc06 100644
>>> --- a/gcc/cp/pt.cc
>>> +++ b/gcc/cp/pt.cc
>>> @@ -13310,6 +13310,19 @@ extract_locals_r (tree *tp, int *walk_subtrees,
>>> void *data_)
>>>        /* Remember local typedefs (85214).  */
>>>        tp = &TYPE_NAME (*tp);
>>>    
>>
>> Please add a comment explaining why it needs to be null.
>>
>> Also, how about a generic _EXTRA_ARGS accessor so places like this don't need
>> to check each code themselves?
> 
> Sounds good.
> 
>>
>>> +  if (has_extra_args_mechanism_p (*tp))
>>> +    {
>>> +      if (PACK_EXPANSION_P (*tp))
>>> +	gcc_checking_assert (!PACK_EXPANSION_EXTRA_ARGS (*tp));
>>> +      else if (TREE_CODE (*tp) == REQUIRES_EXPR)
>>> +	gcc_checking_assert (!REQUIRES_EXPR_EXTRA_ARGS (*tp));
>>> +      else if (TREE_CODE (*tp) == IF_STMT
>>> +	       && IF_STMT_CONSTEXPR_P (*tp))
>>> +	gcc_checking_assert (!IF_STMT_EXTRA_ARGS (*tp));
>>> +      else
>>> +	gcc_unreachable ();
>>> +    }
>>> +
>>>      if (TREE_CODE (*tp) == DECL_EXPR)
>>>        {
>>>          tree decl = DECL_EXPR_DECL (*tp);
>>> @@ -18738,7 +18751,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
>>> complain, tree in_decl)
>>>    	  IF_COND (stmt) = IF_COND (t);
>>>    	  THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
>>>    	  ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
>>> -	  IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
>>> +	  IF_SCOPE (stmt) = NULL_TREE;
>>
>> What does IF_SCOPE have to do with this?
> 
> IF_SCOPE is the same field as IF_STMT_EXTRA_ARGS so we need to clear it
> before calling build_extra_args to avoid tripping over the added assert.

Let's clear it a few lines earlier, then, immediately after the 
poplevel; OK with that change.

finish_if_stmt clears it even before calling poplevel, but that doesn't 
seem necessary.

Jason