[PATCH] c++: fix ICE with designated initializer [PR110114]

[Marek Polacek <polacek@redhat.com>]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --

r13-1227 added an assert checking that the index in a CONSTRUCTOR
is a FIELD_DECL.  That's a reasonable assumption but in this case
we never called reshape_init due to the type being incomplete, and
so the index remained an identifier node: get_class_binding never
got around to looking up the FIELD_DECL.

We can avoid the crash by returning early in build_aggr_conv; we'd
return NULL anyway due to:

  if (i < CONSTRUCTOR_NELTS (ctor))
    return NULL;

	PR c++/110114

gcc/cp/ChangeLog:

	* call.cc (build_aggr_conv): Return early if the type isn't
	complete.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/desig28.C: New test.
	* g++.dg/cpp2a/desig29.C: New test.
---
 gcc/cp/call.cc                       |  5 +++++
 gcc/testsuite/g++.dg/cpp2a/desig28.C | 17 +++++++++++++++++
 gcc/testsuite/g++.dg/cpp2a/desig29.C | 10 ++++++++++
 3 files changed, 32 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index b55230d98aa..0af20a81717 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -986,6 +986,11 @@ build_aggr_conv (tree type, tree ctor, int flags, tsubst_flags_t complain)
   tree empty_ctor = NULL_TREE;
   hash_set<tree, true> pset;
 
+  /* We've called complete_type on TYPE before calling this function, but
+     perhaps it wasn't successful.  */
+  if (!COMPLETE_TYPE_P (type))
+    return nullptr;
+
   /* We already called reshape_init in implicit_conversion, but it might not
      have done anything in the case of parenthesized aggr init.  */
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
new file mode 100644
index 00000000000..b63265fea51
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
@@ -0,0 +1,17 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct A {
+    int a,b;
+};
+
+struct B;
+
+void foo(const A &) {}
+void foo(const B &) {}
+
+int
+main ()
+{
+  foo({.a=0});
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
new file mode 100644
index 00000000000..bd1a82b041d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
@@ -0,0 +1,10 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct B;
+
+void foo(const B &) {}
+
+int main() {
+    foo({.a=0}); // { dg-error "invalid" }
+}

base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832
-- 
2.41.0