[TRY] enumerate list of unavailable target features

Author: sayantn

.github/workflows/main.yml

@@ -40,6 +40,7 @@ jobs:
     name: Test
     runs-on: ${{ matrix.target.os }}
     strategy:
+      fail-fast: true
       matrix:
         profile:
         - dev

crates/std_detect/src/detect/macros.rs

@@ -14,6 +14,20 @@ macro_rules! detect_feature {
     };
 }
 
+#[macro_export]
+macro_rules! detect_feature_direct {
+    ($feature:tt, $feature_lit:tt) => {
+        $crate::detect_feature_direct!($feature, $feature_lit : $feature_lit)
+    };
+    ($feature:tt, $feature_lit:tt : $($target_feature_lit:tt),*) => {
+        $(cfg!(target_feature = $target_feature_lit) ||)*
+            $crate::detect::check_for($crate::detect::Feature::$feature)
+    };
+    ($feature:tt, $feature_lit:tt, without cfg check: true) => {
+        $crate::detect::check_for($crate::detect::Feature::$feature)
+    };
+}
+
 #[allow(unused_macros, reason = "it's used in the features! macro below")]
 macro_rules! check_cfg_feature {
     ($feature:tt, $feature_lit:tt) => {
@@ -140,6 +154,20 @@ macro_rules! features {
             )*
         }
 
+        #[test]
+        #[cfg($cfg)]
+        fn all_present() {
+            let mut all_present = true;
+            $(
+                let present = $crate::detect_feature_direct!($feature, $feature_lit $(, without cfg check: $feature_cfg_check)? $(: $($target_feature_lit),*)?);
+                all_present &= present;
+                if !present {
+                    println!("{} not available", $feature_lit);
+                }
+            )*
+            assert!(all_present, "not all features are available");
+        }
+
         /// Each variant denotes a position in a bitset for a particular feature.
         ///
         /// PLEASE: do not use this, it is an implementation detail subject