From 682d401a6ba723b2bf98779d056efc8ff2640178 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Sun, 11 Jun 2023 11:09:16 -0400
Subject: [PATCH] c++: extend lookup_template_class shortcut [PR110122]
Here when substituting the injected class name A during regeneration of
the lambda, we find ourselves in lookup_template_class for A<V> with
V=_ZTAXtl3BarEE (i.e. the template parameter object for Foo{}). The call
to coerce_template_parms within then undesirably tries to make a copy of
this class NTTP argument, which fails because Foo is not copyable. But it
seems clear that this testcase shouldn't require copyability of Foo.
lookup_template_class has a shortcut for looking up the current class
scope, which would avoid the problematic coerce_template_parms call, but
the shortcut doesn't trigger because it only considers the innermost
class scope which in this case in the lambda type. So this patch fixes
this by extending the lookup_template_class shortcut to consider outer
class scopes too (and skipping over lambda types since they are never
specialized from lookup_template_class). We also need to avoid calling
coerce_template_parms when specializing a templated non-template nested
class for the first time (such as A::B in the testcase). Coercion should
be unnecessary there because the innermost arguments belong to the context
and so should have already been coerced.
PR c++/110122
gcc/cp/ChangeLog:
* pt.cc (lookup_template_class): Extend shortcut for looking up the
current class scope to consider outer class scopes too, and use
current_nonlambda_class_type instead of current_class_type. Only
call coerce_template_parms when specializing a primary template.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/nontype-class57.C: New test.
* g++.dg/cpp2a/nontype-class58.C: New test.
---
gcc/cp/pt.cc | 19 +++++++++++----
gcc/testsuite/g++.dg/cpp2a/nontype-class57.C | 25 ++++++++++++++++++++
gcc/testsuite/g++.dg/cpp2a/nontype-class58.C | 20 ++++++++++++++++
3 files changed, 60 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class57.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/nontype-class58.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 6a2cf2c123fb..2345a18becc1 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -9918,16 +9918,27 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context,
template. */
/* Shortcut looking up the current class scope again. */
- if (current_class_type)
- if (tree ti = CLASSTYPE_TEMPLATE_INFO (current_class_type))
+ for (tree cur = current_nonlambda_class_type ();
+ cur != NULL_TREE;
+ cur = get_containing_scope (cur))
+ {
+ if (!CLASS_TYPE_P (cur))
+ continue;
+
+ tree ti = CLASSTYPE_TEMPLATE_INFO (cur);
+ if (!ti || arg_depth > TMPL_ARGS_DEPTH (TI_ARGS (ti)))
+ break;
+
if (gen_tmpl == most_general_template (TI_TEMPLATE (ti))
&& comp_template_args (arglist, TI_ARGS (ti)))
- return current_class_type;
+ return cur;
+ }
/* Calculate the BOUND_ARGS. These will be the args that are
actually tsubst'd into the definition to create the
instantiation. */
- arglist = coerce_template_parms (parmlist, arglist, gen_tmpl, complain);
+ if (PRIMARY_TEMPLATE_P (gen_tmpl))
+ arglist = coerce_template_parms (parmlist, arglist, gen_tmpl, complain);
if (arglist == error_mark_node)
/* We were unable to bind the arguments. */
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class57.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class57.C
new file mode 100644
index 000000000000..1520fc59f647
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class57.C
@@ -0,0 +1,25 @@
+// PR c++/110122
+// { dg-do compile { target c++20 } }
+
+struct Foo {
+ Foo() = default;
+ Foo(const Foo&) = delete;
+};
+
+template<Foo V>
+struct A {
+ A() {
+ [] { A a; }();
+ [this] { this; }();
+ }
+
+ struct B {
+ B() {
+ [] { A a; }();
+ [this] { this; }();
+ }
+ };
+};
+
+A<Foo{}> a;
+A<Foo{}>::B b;
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class58.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class58.C
new file mode 100644
index 000000000000..5bb335ca9e77
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class58.C
@@ -0,0 +1,20 @@
+// PR c++/110122
+// { dg-do compile { target c++20 } }
+
+struct Foo {
+ Foo() = default;
+ constexpr Foo(const Foo&) { }
+};
+
+struct Bar {
+ Foo _;
+};
+
+template<Bar V>
+struct A {
+ A() {
+ [](auto){ A<V> d; }(0); // { dg-bogus "used before its definition" }
+ };
+};
+
+A<Bar{}> a;
--
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