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

Here we're 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
selected function is consteval.  This patch fixes this by checking the
result of extract_call_expr accordingly.  (Note that we can't check
DECL_IMMEDIATE_FUNCTION_P here because we don't know which function was
selected by overload resolution from here.)

	PR c++/105912

gcc/cp/ChangeLog:

	* call.cc (extract_call_expr): Return a NULL_TREE on failure
	instead of asserting.
	* 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.

(cherry picked from commit f70c18524221dcefa6cd26cee7b55503181bd912)

3 files changed, 36 insertions, 9 deletions

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index dafcdb08acb..67c30f380f2 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7116,9 +7116,10 @@ extract_call_expr (tree call)
       default:;
       }
 
-  gcc_assert (TREE_CODE (call) == CALL_EXPR
-	      || TREE_CODE (call) == AGGR_INIT_EXPR
-	      || call == error_mark_node);
+  if (TREE_CODE (call) != CALL_EXPR
+      && TREE_CODE (call) != AGGR_INIT_EXPR
+      && call != error_mark_node)
+    return NULL_TREE;
   return call;
 }
 
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index cf4ae7775da..80fadead0f7 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21069,12 +21069,12 @@ tsubst_copy_and_build (tree t,
 	    bool ord = CALL_EXPR_ORDERED_ARGS (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;
+		}
 	  }
 
 	RETURN (ret);
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>();