[PATCH v2] c++: fix ICE with consteval functions in template decls [PR122658]

[Daniele Sahebi]

Fixed what was asked.
Bootstrapped and regtested on x86_64-linux-unknown-gnu, please tell me
if there are any other issues.

---
Currently, build_over_call calls build_cplus_new in template decls, generating
a TARGET_EXPR that it then passes to fold_non_dependent_expr, which ends up
calling tsubst_expr, and since tsubst_expr doesn't handle TARGET_EXPRs, it ICEs.

Since there is no way for this code path to be executed without causing an
ICE, I believe it can be removed.

        PR c++/122658

gcc/cp/ChangeLog:

        * call.cc (build_over_call): Remove if block that ICEs.

gcc/testsuite/ChangeLog:

        * g++.dg/pr122658.C: New test.

Co-authored-by: Jakub Jelinek <ja...@redhat.com>
---
 gcc/cp/call.cc                  | 13 +++----------
 gcc/testsuite/g++.dg/pr122658.C | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 10 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/pr122658.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index f80d597b3394..7985c2d5e1bb 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -10328,18 +10328,11 @@ build_over_call (struct z_candidate *cand, int flags, 
tsubst_flags_t complain)
        TREE_NO_WARNING (expr) = true;
       if (immediate_invocation_p (fn))
        {
-         tree obj_arg = NULL_TREE, exprimm = expr;
+         tree obj_arg = NULL_TREE;
          if (DECL_CONSTRUCTOR_P (fn))
            obj_arg = first_arg;
-         if (obj_arg
-             && is_dummy_object (obj_arg)
-             && !type_dependent_expression_p (obj_arg))
-           {
-             exprimm = build_cplus_new (DECL_CONTEXT (fn), expr, complain);
-             obj_arg = NULL_TREE;
-           }
          /* Look through *(const T *)&obj.  */
-         else if (obj_arg && INDIRECT_REF_P (obj_arg))
+         if (obj_arg && INDIRECT_REF_P (obj_arg))
            {
              tree addr = TREE_OPERAND (obj_arg, 0);
              STRIP_NOPS (addr);
@@ -10351,7 +10344,7 @@ build_over_call (struct z_candidate *cand, int flags, 
tsubst_flags_t complain)
                    obj_arg = TREE_OPERAND (addr, 0);
                }
            }
-         fold_non_dependent_expr (exprimm, complain,
+         fold_non_dependent_expr (expr, complain,
                                   /*manifestly_const_eval=*/true,
                                   obj_arg);
        }
diff --git a/gcc/testsuite/g++.dg/pr122658.C b/gcc/testsuite/g++.dg/pr122658.C
new file mode 100644
index 000000000000..22b9d3e664ab
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr122658.C
@@ -0,0 +1,15 @@
+/* PR c++/53055 */
+/* { dg-do compile } */
+/* { dg-options "-std=c++20" } */
+
+struct S {
+  consteval S () noexcept { }
+  consteval S (const S &) = default;
+};
+
+template <typename T>
+void
+foo ()
+{
+  constexpr auto s = S();
+}
-- 
2.47.3