[gcc r13-3462] c++: ICE with invalid structured bindings [PR107276]

[gcc r13-3462] c++: ICE with invalid structured bindings [PR107276]

[Marek Polacek]

https://gcc.gnu.org/g:f7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40

commit r13-3462-gf7d8ccfda2d5c90dac97b1a3ede8b10391a3cc40
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Oct 20 15:55:28 2022 -0400

    c++: ICE with invalid structured bindings [PR107276]
    
    This test ICEs in C++23 because we reach the new code in do_auto_deduction:
    
    30468   if (cxx_dialect >= cxx23
    30469       && context == adc_return_type
    30470       && (!AUTO_IS_DECLTYPE (auto_node)
    30471           || !unparenthesized_id_or_class_member_access_p (init))
    30472       && (r = treat_lvalue_as_rvalue_p (maybe_undo_parenthesized_ref (init),
    30473                                         /*return*/true)))
    
    where 'init' is "VIEW_CONVERT_EXPR<<<< error >>>>(y)", and then the move
    in treat_lvalue_as_rvalue_p returns error_mark_node whereupon
    set_implicit_rvalue_p crashes.
    
    I don't think such V_C_Es are useful so let's not create them.  But that
    won't fix the ICE so I'm checking the return value of move.  A structured
    bindings decl can have an error type, that is set in cp_finish_decomp:
    
     8908           TREE_TYPE (first) = error_mark_node;
    
    therefore I think treat_lvalue_as_rvalue_p just needs to cope.
    
            PR c++/107276
    
    gcc/cp/ChangeLog:
    
            * typeck.cc (treat_lvalue_as_rvalue_p): Check the return value of move.
    
    gcc/ChangeLog:
    
            * tree.cc (maybe_wrap_with_location): Don't create a location wrapper
            when the type is erroneous.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/decomp4.C: New test.

Diff:
---
 gcc/cp/typeck.cc                     | 7 ++++++-
 gcc/testsuite/g++.dg/cpp2a/decomp4.C | 8 ++++++++
 gcc/tree.cc                          | 2 +-
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 530d260b1e8..ab6979bcc50 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10729,7 +10729,12 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
   if (DECL_CONTEXT (retval) != current_function_decl)
     return NULL_TREE;
   if (return_p)
-    return set_implicit_rvalue_p (move (expr));
+    {
+      expr = move (expr);
+      if (expr == error_mark_node)
+	return NULL_TREE;
+      return set_implicit_rvalue_p (expr);
+    }
 
   /* if the operand of a throw-expression is a (possibly parenthesized)
      id-expression that names an implicitly movable entity whose scope does not
diff --git a/gcc/testsuite/g++.dg/cpp2a/decomp4.C b/gcc/testsuite/g++.dg/cpp2a/decomp4.C
new file mode 100644
index 00000000000..d1b0c90ee26
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/decomp4.C
@@ -0,0 +1,8 @@
+// PR c++/107276
+// { dg-do compile { target c++20 } }
+
+auto f(auto x) {
+  auto [y] = x; // { dg-error "cannot decompose" }
+  return y;
+}
+int i = f(0);
diff --git a/gcc/tree.cc b/gcc/tree.cc
index 81a6ceaf181..04603c8c902 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -14352,7 +14352,7 @@ maybe_wrap_with_location (tree expr, location_t loc)
 
   /* For now, don't add wrappers to exceptional tree nodes, to minimize
      any impact of the wrapper nodes.  */
-  if (EXCEPTIONAL_CLASS_P (expr))
+  if (EXCEPTIONAL_CLASS_P (expr) || error_operand_p (expr))
     return expr;
 
   /* Compiler-generated temporary variables don't need a wrapper.  */