Remove msrv_1_77 feature

Use `autocfg` to detect Rust >=1.77

Author: bushrat011899

Cargo.toml

@@ -27,10 +27,6 @@ default = ["std"]
 libm = ["dep:libm"]
 std = []
 
-# Allows access to functionality only available in Rust 1.77, such as round_ties_even
-# This increases the MSRV to 1.77
-msrv_1_77 = []
-
 # vestigial features, now always in effect
 i128 = []
 

build.rs

@@ -2,6 +2,7 @@ fn main() {
     let ac = autocfg::new();
 
     ac.emit_expression_cfg("1f64.total_cmp(&2f64)", "has_total_cmp"); // 1.62
+    ac.emit_expression_cfg("1.5f64.round_ties_even()", "has_round_ties_even"); // 1.77
 
     autocfg::rerun_path("build.rs");
 }

src/float.rs

@@ -869,7 +869,7 @@ impl FloatCore for f32 {
         Self::powi(self, n: i32) -> Self;
     }
 
-    #[cfg(all(feature = "std", feature = "msrv_1_77"))]
+    #[cfg(all(feature = "std", has_round_ties_even))]
     forward! {
         Self::round_ties_even(self) -> Self;
     }
@@ -936,7 +936,7 @@ impl FloatCore for f64 {
         Self::powi(self, n: i32) -> Self;
     }
 
-    #[cfg(all(feature = "std", feature = "msrv_1_77"))]
+    #[cfg(all(feature = "std", has_round_ties_even))]
     forward! {
         Self::round_ties_even(self) -> Self;
     }
@@ -2549,7 +2549,7 @@ mod tests {
     /// Compares the fallback implementation of [`round_ties_even`] to the one provided by `f32`.`
     ///
     /// [`round_ties_even`]: crate::float::FloatCore::round_ties_even
-    #[cfg(feature = "msrv_1_77")]
+    #[cfg(has_round_ties_even)]
     #[test]
     fn round_ties_even() {
         mod wrapped_f32 {