[libc++] [test] Rationalize the nodiscard tests for range adaptors.

Reviewed as part of D115177.

Author: Quuxplusone

libcxx/test/libcxx/ranges/range.adaptors/range.all/all.nodiscard.verify.cpp

@@ -16,10 +16,8 @@
 
 void test() {
   int range[] = {1, 2, 3};
-  auto f = [](int i) { return i; };
 
   std::views::all(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   range | std::views::all; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::views::transform(f) | std::views::all; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::views::all | std::views::transform(f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::views::all | std::views::all; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }

libcxx/test/libcxx/ranges/range.adaptors/range.common.view/adaptor.nodiscard.verify.cpp

@@ -10,8 +10,7 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
 
-// Test the libc++ extension that std::views::common is marked as [[nodiscard]] to avoid
-// the potential for user mistakenly thinking they're calling an algorithm.
+// Test the libc++ extension that std::views::common is marked as [[nodiscard]].
 
 #include <ranges>
 
@@ -20,4 +19,5 @@ void test() {
 
   std::views::common(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   range | std::views::common; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::views::all | std::views::common; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }

libcxx/test/std/ranges/range.adaptors/range.reverse/adaptor.nodiscard.verify.cpp renamed to libcxx/test/libcxx/ranges/range.adaptors/range.reverse/adaptor.nodiscard.verify.cpp

@@ -9,10 +9,8 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
-// REQUIRES: libc++
 
-// Test the libc++ extension that std::views::reverse is marked as [[nodiscard]] to avoid
-// the potential for user mistakenly thinking they're calling an algorithm.
+// Test the libc++ extension that std::views::reverse is marked as [[nodiscard]].
 
 #include <ranges>
 
@@ -21,5 +19,5 @@ void test() {
 
   std::views::reverse(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   range | std::views::reverse; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::views::reverse | std::views::reverse; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::views::all | std::views::reverse; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }

libcxx/test/libcxx/ranges/range.adaptors/range.transform/adaptor.nodiscard.verify.cpp

@@ -10,8 +10,7 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
 
-// Test the libc++ extension that std::views::transform is marked as [[nodiscard]] to avoid
-// the potential for user mistakenly thinking they're calling an algorithm.
+// Test the libc++ extension that std::views::transform is marked as [[nodiscard]].
 
 #include <ranges>
 
@@ -22,5 +21,5 @@ void test() {
   std::views::transform(f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   std::views::transform(range, f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   range | std::views::transform(f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
-  std::views::transform(f) | std::views::transform(f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::views::all | std::views::transform(f); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }