wip: use trait

Author: chansuke

src/env_var.rs

@@ -1,12 +1,23 @@
 use std::collections::HashSet;
 use std::env;
+use std::ffi::OsStr;
 use std::path::PathBuf;
 use std::process::Command;
 
 use crate::process;
 
 pub const RUST_RECURSION_COUNT_MAX: u32 = 20;
 
+trait ProcessEnvs {
+    type Item;
+    type Iter: Iterator;
+    fn get_envs(&self) -> Self::Iter<Item=Self::Item>;
+    fn env<K, V>(&mut self, key: K, val: V) -> &mut Self
+where
+    K: AsRef<OsStr>,
+    V: AsRef<OsStr>;
+}
+
 #[allow(unused)]
 pub fn append_path(name: &str, value: Vec<PathBuf>, cmd: &mut Command) {
     let old_value = process().var_os(name);