[gcc r14-8697] c++: ICE with throw inside concept [PR112437]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:65b105b4f399559685200e1598ead8c7d0935c04

commit r14-8697-g65b105b4f399559685200e1598ead8c7d0935c04
Author: Marek Polacek <polacek@redhat.com>
Date:   Wed Jan 31 17:33:26 2024 -0500

    c++: ICE with throw inside concept [PR112437]
    
    We crash in the loop at the end of treat_lvalue_as_rvalue_p for code
    like
    
      template <class T>
      concept Throwable = requires(T x) { throw x; };
    
    because the code assumes that we eventually reach sk_function_parms or
    sk_try and bail, but in a concept we're in a sk_namespace.
    
    We're already checking sk_try so we don't crash in a function-try-block,
    but I've added a test anyway.
    
            PR c++/112437
    
    gcc/cp/ChangeLog:
    
            * typeck.cc (treat_lvalue_as_rvalue_p): Bail out on sk_namespace in
            the move on throw of parms loop.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/concepts-throw1.C: New test.
            * g++.dg/eh/throw4.C: New test.

Diff:
---
 gcc/cp/typeck.cc                             |  4 +++-
 gcc/testsuite/g++.dg/cpp2a/concepts-throw1.C |  8 ++++++++
 gcc/testsuite/g++.dg/eh/throw4.C             | 13 +++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index a15eda3f5f8c..4937022ff207 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10863,7 +10863,9 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
       for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
 	if (decl == retval)
 	  return set_implicit_rvalue_p (move (expr));
-      if (b->kind == sk_function_parms || b->kind == sk_try)
+      if (b->kind == sk_function_parms
+	  || b->kind == sk_try
+	  || b->kind == sk_namespace)
 	return NULL_TREE;
     }
 }
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-throw1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-throw1.C
new file mode 100644
index 000000000000..bc3e3b6891ab
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-throw1.C
@@ -0,0 +1,8 @@
+// PR c++/112437
+// { dg-do compile { target c++20 } }
+
+struct S {};
+template <class T>
+concept Throwable = requires(T x) { throw x; };
+
+bool a = Throwable<S>;
diff --git a/gcc/testsuite/g++.dg/eh/throw4.C b/gcc/testsuite/g++.dg/eh/throw4.C
new file mode 100644
index 000000000000..b474472de489
--- /dev/null
+++ b/gcc/testsuite/g++.dg/eh/throw4.C
@@ -0,0 +1,13 @@
+// PR c++/112437
+// { dg-do compile }
+
+struct S {};
+
+S
+foo (S s)
+try {
+  throw s;
+}
+catch (...) {
+  throw s;
+}