On 3/14/26 4:12 PM, Jakub Jelinek wrote:
On Sat, Mar 14, 2026 at 03:50:17PM -0400, Jason Merrill wrote:
There's a second fallback (to tsubst_decl) after name lookup, I would think
that we just want to skip the lookup if DECL_NAME is null.
From quick testing, this seems to work too.
Ok for trunk if it passes full bootstrap/regtest?
OK.
2026-03-14 Jakub Jelinek <[email protected]>
PR c++/120039
PR c++/122559
* pt.cc (tsubst_expr) <case VAR_DECL>: Don't call lookup_name on
DECL_NAME (t) if it is NULL_TREE.
* g++.dg/cpp26/decomp28.C: New test.
* g++.dg/cpp26/decomp29.C: New test.
--- gcc/cp/pt.cc.jj 2026-03-14 09:46:16.671478112 +0100
+++ gcc/cp/pt.cc 2026-03-14 21:06:22.139092954 +0100
@@ -22731,7 +22731,8 @@ tsubst_expr (tree t, tree args, tsubst_f
else if (r == NULL_TREE)
{
/* First try name lookup to find the instantiation. */
- r = lookup_name (DECL_NAME (t));
+ if (DECL_NAME (t))
+ r = lookup_name (DECL_NAME (t));
if (r)
{
if (!VAR_P (r))
--- gcc/testsuite/g++.dg/cpp26/decomp28.C.jj 2026-03-14 21:05:50.802252148
+0100
+++ gcc/testsuite/g++.dg/cpp26/decomp28.C 2026-03-14 21:05:50.802252148
+0100
@@ -0,0 +1,23 @@
+// PR c++/120039
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+struct S {
+ int a; long long b; short c;
+ explicit operator bool () const noexcept { return true; }
+};
+
+template <int N>
+void
+foo ()
+{
+ S s = S { 1, 2, 3 };
+ if (auto [sx, sy, sz] : s) // { dg-warning "structured bindings in conditions only
available with" "" { target c++23_down } }
+ ; // { dg-error "expected initializer before ':' token"
"" { target *-*-* } .-1 }
+} // { dg-error "expected '\\\)' before ':' token"
"" { target *-*-* } .-2 }
+
+int
+main ()
+{
+ foo <0> ();
+}
--- gcc/testsuite/g++.dg/cpp26/decomp29.C.jj 2026-03-14 21:05:50.802350073
+0100
+++ gcc/testsuite/g++.dg/cpp26/decomp29.C 2026-03-14 21:05:50.802350073
+0100
@@ -0,0 +1,19 @@
+// PR c++/122559
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+enum class A : bool { B, C };
+
+template <typename T>
+A type (T &&x)
+{
+ if (auto [value = x ()]) // { dg-warning "structured bindings in conditions only
available with" "" { target c++23_down } }
+ return A::C; // { dg-error "expected '\\\]' before '=' token"
"" { target *-*-* } .-1 }
+ return A::B; // { dg-error "expected initializer before '\\\)' token"
"" { target *-*-* } .-2 }
+}
+
+int
+main ()
+{
+ auto _ = type (A::B);
+}
Jakub
