Delete no_try_from config for rustc older than 1.34

Author: dtolnay

build.rs

@@ -58,10 +58,6 @@ fn main() {
         println!("cargo:rustc-cfg=span_locations");
     }
 
-    if version.minor < 34 {
-        println!("cargo:rustc-cfg=no_try_from");
-    }
-
     if version.minor < 39 {
         println!("cargo:rustc-cfg=no_bind_by_move_pattern_guard");
     }

src/convert.rs

@@ -1,17 +1,3 @@
 pub(crate) fn usize_to_u32(u: usize) -> Option<u32> {
-    #[cfg(not(no_try_from))]
-    {
-        u32::try_from(u).ok()
-    }
-
-    #[cfg(no_try_from)]
-    {
-        use core::mem;
-
-        if mem::size_of::<usize>() <= mem::size_of::<u32>() || u <= u32::max_value() as usize {
-            Some(u as u32)
-        } else {
-            None
-        }
-    }
+    u32::try_from(u).ok()
 }