[PATCH] c++: non-dependent call to consteval operator [PR105912]

[Patrick Palka via Gcc-patches]

Here we were crashing when substituting a non-dependent call to a
consteval operator, whose CALL_EXPR_OPERATOR_SYNTAX flag we try to
propagate to the result, but the result isn't a CALL_EXPR since the
called function is consteval.  This patch fixes this by checking the
result of extract_call_expr accordingly.  (Note that we can't easily
check DECL_IMMEDIATE_FUNCTION_P here because we don't know which
function was selected by overload resolution from this call frame.)

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
for trunk/12?

        PR c++/105912

gcc/cp/ChangeLog:

        * pt.cc (tsubst_copy_and_build) <case CALL_EXPR>: Guard against
        NULL_TREE extract_call_expr result.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/consteval31.C: New test.
---
 gcc/cp/pt.cc                             | 10 +++++----
 gcc/testsuite/g++.dg/cpp2a/consteval31.C | 26 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/consteval31.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 232964c2831..8a6ae5c42fe 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21207,10 +21207,12 @@ tsubst_copy_and_build (tree t,
            bool rev = CALL_EXPR_REVERSE_ARGS (t);
            if (op || ord || rev)
              {
-               function = extract_call_expr (ret);
-               CALL_EXPR_OPERATOR_SYNTAX (function) = op;
-               CALL_EXPR_ORDERED_ARGS (function) = ord;
-               CALL_EXPR_REVERSE_ARGS (function) = rev;
+               if (tree call = extract_call_expr (ret))
+                 {
+                   CALL_EXPR_OPERATOR_SYNTAX (call) = op;
+                   CALL_EXPR_ORDERED_ARGS (call) = ord;
+                   CALL_EXPR_REVERSE_ARGS (call) = rev;
+                 }
              }
          }
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval31.C 
b/gcc/testsuite/g++.dg/cpp2a/consteval31.C
new file mode 100644
index 00000000000..85a4d1794e5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/consteval31.C
@@ -0,0 +1,26 @@
+// PR c++/105912
+// { dg-do compile { target c++20 } }
+
+struct A {
+  consteval A operator+() {
+    return {};
+  }
+};
+
+consteval A operator~(A) {
+  return {};
+}
+
+consteval A operator+(A, A) {
+  return {};
+}
+
+template<class>
+void f() {
+  A a;
+  ~a;
+  a + a;
+  +a;
+}
+
+template void f<int>();
-- 
2.37.0.3.g30cc8d0f14