[gcc/devel/c++-contracts] c++: disable constexpr assume contract special handling

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:61b1ec945d6ec8a7580980507f732789b0f8ca87

commit 61b1ec945d6ec8a7580980507f732789b0f8ca87
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Oct 17 15:58:03 2022 -0400

    c++: disable constexpr assume contract special handling
    
    This code was trying to avoid instantiating for an assumed contract, but the
    instantiation in contracts-assume6.C was happening earlier.  Now it doesn't,
    but the testcase still expects it.  So disable this code for now.
    
    gcc/cp/ChangeLog:
    
            * constexpr.cc (cxx_eval_constant_expression): Don't try to avoid
            instantiation for CCS_ASSUME.

Diff:
---
 gcc/cp/constexpr.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 09267e538a8..57617847634 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -7740,11 +7740,14 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 	tree c = CONTRACT_CONDITION (t);
 	if (semantic == CCS_ASSUME)
 	  {
+#if 0
 	    /* For an assume contract, try evaluating it without instantiating
 	       anything.  If non-constant, assume it's satisfied.  */
+	    /* This breaks contracts-assume6.C.  */
 
 	    if (!cp_tree_defined_p (c))
 	      break;
+#endif
 
 	    bool dummy_nc = false, dummy_ov = false;
 	    constexpr_ctx new_ctx = *ctx;