[C++ PATCH] PR c++/92560 - ICE with decltype and rewritten operator.

[Jason Merrill]

A call as the immediate operand of decltype is handled differently; we don't
create an object of the return type as we do normally.  But in the case of a
rewritten operator, we're adding another call as a wrapper, so the inner
call doesn't get the special handling.

Tested x86_64-pc-linux-gnu, applying to trunk.

	* call.c (build_new_op_1): Clear tf_decltype on inner call.
---
 gcc/cp/call.c                                    |  6 +++++-
 gcc/testsuite/g++.dg/cpp2a/spaceship-decltype1.C | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/spaceship-decltype1.C

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index ce942977f45..48d49b7ec87 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -6242,6 +6242,10 @@ build_new_op_1 (const op_location_t &loc, enum tree_code code, int flags,
 	    result = error_mark_node;
 	  else
 	    {
+	      tsubst_flags_t ocomplain = complain;
+	      if (cand->rewritten ())
+		/* We'll wrap this call in another one.  */
+		ocomplain &= ~tf_decltype;
 	      if (cand->reversed ())
 		{
 		  /* We swapped these in add_candidate, swap them back now.  */
@@ -6251,7 +6255,7 @@ build_new_op_1 (const op_location_t &loc, enum tree_code code, int flags,
 				"current function recursively with reversed "
 				"arguments");
 		}
-	      result = build_over_call (cand, LOOKUP_NORMAL, complain);
+	      result = build_over_call (cand, LOOKUP_NORMAL, ocomplain);
 	    }
 
 	  if (trivial_fn_p (cand->fn))
diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-decltype1.C b/gcc/testsuite/g++.dg/cpp2a/spaceship-decltype1.C
new file mode 100644
index 00000000000..bc673b2e020
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-decltype1.C
@@ -0,0 +1,11 @@
+// PR c++/92560
+// { dg-do compile { target c++2a } }
+
+#include <compare>
+
+struct X
+{
+  friend std::strong_ordering operator<=>(X, X);
+} x;
+
+using T = decltype(x < x);

base-commit: b746406f8489fd246aabe01bdf0fc2f319be5b05
-- 
2.18.1