[PATCH] c++: Don't ICE in build_class_member_access_expr during error recovery [PR118225]

[Simon Martin]

The invalid case in this PR trips on an assertion in
build_class_member_access_expr that build_base_path would never return
an error_mark_node, which is actually incorrect if the object involves a
tree with an error_mark_node DECL_INITIAL, like here.

This patch simply removes the assertion, even though it has been here
for 22+ years (r0-44513-g50ad96428042fa). An alternative would be to
assert that object != error_mark_node || seen_error (), but that'd be
virtually not asserting anything IMO.

Successfully tested on x86_64-pc-linux-gnu.

        PR c++/118225

gcc/cp/ChangeLog:

        * typeck.cc (build_class_member_access_expr): Remove incorrect
        gcc_assert.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/constexpr-ice21.C: New test.

---
 gcc/cp/typeck.cc                             |  3 ---
 gcc/testsuite/g++.dg/cpp0x/constexpr-ice21.C | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-ice21.C

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 1f9a74166f4..14912254c9c 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -2978,9 +2978,6 @@ build_class_member_access_expr (cp_expr object, tree 
member,
          /* Convert to the base.  */
          object = build_base_path (PLUS_EXPR, object, binfo,
                                    /*nonnull=*/1, complain);
-         /* If we found the base successfully then we should be able
-            to convert to it successfully.  */
-         gcc_assert (object != error_mark_node);
        }
 
       /* If MEMBER is from an anonymous aggregate, we have converted
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice21.C 
b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice21.C
new file mode 100644
index 00000000000..46273654f24
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice21.C
@@ -0,0 +1,17 @@
+// PR c++/118225
+// { dg-do "compile" { target c++11} }
+
+struct NoMut1 { int a, b; };
+struct NoMut3 : virtual NoMut1 {
+  constexpr NoMut3(int a, int b) // { dg-error "virtual base" "" { target 
c++23 } }
+    : NoMut1{a, b}
+  {} // { dg-error "virtual base" }
+};
+void mutable_subobjects() {
+  constexpr NoMut3 nm3 = {1, 2}; // { dg-error "call to non" }
+  struct A {
+    void f() {
+      static_assert(nm3.a == 1, ""); // { dg-error "local variable" }
+    }
+  };
+}
-- 
2.44.0