Explain passing template function as an argument

JMazurkiewicz · JMazurkiewicz · commit 50d40239e22a · 2024-03-14T13:45:05.000+01:00
Addresses (maybe) #81055 (comment)
diff --git a/libcxx/test/std/utilities/function.objects/func.bind.partial/bind_back.verify.cpp b/libcxx/test/std/utilities/function.objects/func.bind.partial/bind_back.verify.cpp
@@ -25,8 +25,9 @@ void test() {
     static_assert(f1() == 1); // expected-error {{static assertion expression is not an integral constant expression}}
   }
 
-  { // Various failures
-    auto d = std::bind_back(do_nothing, 2); // expected-error {{no matching function for call to 'bind_back'}}
+  { // Test calling `bind_back` with template function
+    auto f1 = std::bind_back(do_nothing, 2);
+    // expected-error@-1 {{no matching function for call to 'bind_back'}}
   }
 
   { // Mandates: is_constructible_v<decay_t<F>, F>

Original file line number	Diff line number	Diff line change
`@@ -25,8 +25,9 @@ void test() {`
`25`	`25`	`static_assert(f1() == 1); // expected-error {{static assertion expression is not an integral constant expression}}`
`26`	`26`	`}`
`27`	`27`
`28`		`- { // Various failures`
`29`		`- auto d = std::bind_back(do_nothing, 2); // expected-error {{no matching function for call to 'bind_back'}}`
	`28`	+ { // Test calling `bind_back` with template function
	`29`	`+ auto f1 = std::bind_back(do_nothing, 2);`
	`30`	`+ // expected-error@-1 {{no matching function for call to 'bind_back'}}`
`30`	`31`	`}`
`31`	`32`
`32`	`33`	`{ // Mandates: is_constructible_v<decay_t<F>, F>`