Document why we map type_ to type

Author: gnzlbg

libc-test/build.rs

@@ -1022,14 +1022,9 @@ fn test_dragonflybsd(target: &str) {
                 s.replace("e_nsec", ".tv_nsec")
             }
             "u64" if struct_ == "epoll_event" => "data.u64".to_string(),
-            "type_"
-                if struct_ == "input_event"
-                    || struct_ == "input_mask"
-                    || struct_ == "ff_effect"
-                    || struct_ == "rtprio" =>
-            {
-                "type".to_string()
-            }
+            // Field is named `type` in C but that is a Rust keyword,
+            // so these fields are translated to `type_` in the bindings.
+            "type_" if struct_ == "rtprio" => "type".to_string(),
             s => s.to_string(),
         }
     });
@@ -1555,7 +1550,10 @@ fn test_freebsd(target: &str) {
             s if s.ends_with("_nsec") && struct_.starts_with("stat") => {
                 s.replace("e_nsec", ".tv_nsec")
             }
-          s => s.to_string(),
+            // Field is named `type` in C but that is a Rust keyword,
+            // so these fields are translated to `type_` in the bindings.
+            "type_" if struct_ == "rtprio" => "type".to_string(),
+            s => s.to_string(),
         }
     });
 
@@ -2313,12 +2311,13 @@ fn test_linux(target: &str) {
             }
             // FIXME: is this necessary?
             "u64" if struct_ == "epoll_event" => "data.u64".to_string(),
-            // FIXME: is this necessary?
+            // The following structs have a field called `type` in C,
+            // but `type` is a Rust keyword, so these fields are translated
+            // to `type_` in Rust.
             "type_"
                 if struct_ == "input_event"
                     || struct_ == "input_mask"
-                    || struct_ == "ff_effect"
-                    || struct_ == "rtprio" =>
+                    || struct_ == "ff_effect" =>
             {
                 "type".to_string()
             }