refactor: Remove vec_map dependency

Doesn't look like this dependency is buying us anything at this point,
so removing it.

Cargo.toml

@@ -65,7 +65,6 @@ bitflags = "1.2"
 textwrap = { version = "0.14.0", default-features = false, features = [] }
 indexmap = "1.0"
 os_str_bytes = "4.1"
-vec_map = "0.8"
 strsim = { version = "0.10",  optional = true }
 yaml-rust = { version = "0.4.1",  optional = true }
 atty = { version = "0.2",  optional = true }

src/build/arg/mod.rs

@@ -31,7 +31,6 @@ use yaml_rust::Yaml;
 // Internal
 use crate::{
     build::{arg::settings::ArgFlags, usage_parser::UsageParser},
-    util::VecMap,
     util::{Id, Key},
     INTERNAL_ERROR_MSG,
 };
@@ -111,7 +110,7 @@ pub struct Arg<'help> {
     pub(crate) validator_os: Option<Arc<Mutex<ValidatorOs<'help>>>>,
     pub(crate) val_delim: Option<char>,
     pub(crate) default_vals: Vec<&'help OsStr>,
-    pub(crate) default_vals_ifs: VecMap<(Id, Option<&'help OsStr>, Option<&'help OsStr>)>,
+    pub(crate) default_vals_ifs: Vec<(Id, Option<&'help OsStr>, Option<&'help OsStr>)>,
     pub(crate) default_missing_vals: Vec<&'help OsStr>,
     #[cfg(feature = "env")]
     pub(crate) env: Option<(&'help OsStr, Option<OsString>)>,
@@ -2938,9 +2937,7 @@ impl<'help> Arg<'help> {
         val: Option<&'help OsStr>,
         default: Option<&'help OsStr>,
     ) -> Self {
-        let l = self.default_vals_ifs.len();
+        self.default_vals_ifs.push((arg_id.into(), val, default));
-        self.default_vals_ifs
-            .insert(l, (arg_id.into(), val, default));
         self.takes_value(true)
     }
 

src/output/help.rs

@@ -215,7 +215,7 @@ impl<'help, 'app, 'parser, 'writer> Help<'help, 'app, 'parser, 'writer> {
                 longest = longest.max(display_width(arg.to_string().as_str()));
                 debug!("Help::write_args: New Longest...{}", longest);
             }
-            let btm = ord_m.entry(arg.disp_ord).or_insert(BTreeMap::new());
+            let btm = ord_m.entry(arg.disp_ord).or_insert_with(BTreeMap::new);
 
             // Formatting key like this to ensure that:
             // 1. Argument has long flags are printed just after short flags.
@@ -873,7 +873,9 @@ impl<'help, 'app, 'parser, 'writer> Help<'help, 'app, 'parser, 'writer> {
             .iter()
             .filter(|subcommand| should_show_subcommand(subcommand))
         {
-            let btm = ord_m.entry(subcommand.disp_ord).or_insert(BTreeMap::new());
+            let btm = ord_m
+                .entry(subcommand.disp_ord)
+                .or_insert_with(BTreeMap::new);
             let mut sc_str = String::new();
             sc_str.push_str(
                 &subcommand

src/parse/parser.rs

@@ -1655,7 +1655,7 @@ impl<'help, 'app> Parser<'help, 'app> {
         if !arg.default_vals_ifs.is_empty() {
             debug!("Parser::add_value: has conditional defaults");
             if matcher.get(&arg.id).is_none() {
-                for (id, val, default) in arg.default_vals_ifs.values() {
+                for (id, val, default) in arg.default_vals_ifs.iter() {
                     let add = if let Some(a) = matcher.get(id) {
                         if let Some(v) = val {
                             a.vals_flatten().any(|value| v == value)

src/util/mod.rs

@@ -11,7 +11,6 @@ pub use self::fnv::Key;
 #[cfg(feature = "env")]
 pub(crate) use self::str_to_bool::str_to_bool;
 pub(crate) use self::{graph::ChildGraph, id::Id};
-pub(crate) use vec_map::VecMap;
 
 #[cfg(feature = "color")]
 pub(crate) use termcolor;