DRAFT: std_detect: Remove support for implied by target_features

This commit tests whether `implied by target_features: [...]` inside
the target description macro `features!` can be removed.

Author: a4lg

library/std_detect/src/detect/macros.rs

@@ -3,11 +3,7 @@
 #[unstable(feature = "stdarch_internal", issue = "none")]
 macro_rules! detect_feature {
     ($feature:tt, $feature_lit:tt) => {
-        $crate::detect_feature!($feature, $feature_lit : $feature_lit)
-    };
-    ($feature:tt, $feature_lit:tt : $($target_feature_lit:tt),*) => {
-        $(cfg!(target_feature = $target_feature_lit) ||)*
-            $crate::detect::__is_feature_detected::$feature()
+        cfg!(target_feature = $feature_lit) || $crate::detect::__is_feature_detected::$feature()
     };
     ($feature:tt, $feature_lit:tt : cfg($target_feature_cfg:meta)) => {
         cfg!($target_feature_cfg) || $crate::detect::__is_feature_detected::$feature()
@@ -20,10 +16,7 @@ macro_rules! detect_feature {
 #[allow(unused_macros, reason = "it's used in the features! macro below")]
 macro_rules! check_cfg_feature {
     ($feature:tt, $feature_lit:tt) => {
-        check_cfg_feature!($feature, $feature_lit : $feature_lit)
-    };
-    ($feature:tt, $feature_lit:tt : $($target_feature_lit:tt),*) => {
-        $(cfg!(target_feature = $target_feature_lit);)*
+        cfg!(target_feature = $feature_lit);
     };
     ($feature:tt, $feature_lit:tt : cfg($target_feature_cfg:meta)) => {
         cfg!($target_feature_cfg);
@@ -47,7 +40,6 @@ macro_rules! features {
       $(@NO_RUNTIME_DETECTION: $nort_feature:tt; )*
       $(@FEATURE: #[$stability_attr:meta] $feature:ident: $feature_lit:tt;
           $(without cfg check: $feature_cfg_check:tt;)?
-          $(implied by target_features: [$($target_feature_lit:tt),*];)?
           $(implied by cfg($target_feature_cfg:meta);)?
           $(#[$feature_comment:meta])*)*
     ) => {
@@ -63,7 +55,6 @@ macro_rules! features {
                         $feature,
                         $feature_lit
                         $(, without cfg check: $feature_cfg_check)?
-                        $(: $($target_feature_lit),*)?
                         $(: cfg($target_feature_cfg))?
                     )
                 };
@@ -154,7 +145,6 @@ macro_rules! features {
                     $feature,
                     $feature_lit
                     $(, without cfg check: $feature_cfg_check)?
-                    $(: $($target_feature_lit),*)?
                     $(: cfg($target_feature_cfg))?
                 );
             )*