Some small clean ups.

crates/mdman/src/hbs.rs

@@ -24,14 +24,13 @@ pub fn expand(file: &Path, formatter: FormatterRef) -> Result<String, Error> {
     handlebars.register_template_file("template", file)?;
     let includes = file.parent().unwrap().join("includes");
     handlebars.register_templates_directory(".md", includes)?;
-    let mut data: HashMap<String, String> = HashMap::new();
     let man_name = file
         .file_stem()
         .expect("expected filename")
         .to_str()
         .expect("utf8 filename")
         .to_string();
-    data.insert("man_name".to_string(), man_name);
+    let data: HashMap<String, String> = [("man_name", man_name)].into();
     let expanded = handlebars.render("template", &data)?;
     Ok(expanded)
 }

src/bin/cargo/commands/verify_project.rs

@@ -13,14 +13,12 @@ pub fn cli() -> App {
 
 pub fn exec(config: &mut Config, args: &ArgMatches) -> CliResult {
     if let Err(e) = args.workspace(config) {
-        let mut h = HashMap::new();
-        h.insert("invalid".to_string(), e.to_string());
+        let h: HashMap<_, _> = [("invalid", e.to_string())].into();
         config.shell().print_json(&h)?;
         process::exit(1)
     }
 
-    let mut h = HashMap::new();
-    h.insert("success".to_string(), "true".to_string());
+    let h: HashMap<_, _> = [("success", "true")].into();
     config.shell().print_json(&h)?;
     Ok(())
 }

src/cargo/core/compiler/rustdoc.rs

@@ -64,8 +64,7 @@ pub struct RustdocExternMap {
 
 impl Default for RustdocExternMap {
     fn default() -> Self {
-        let mut registries = HashMap::new();
-        registries.insert(CRATES_IO_REGISTRY.into(), DOCS_RS_URL.into());
+        let registries = [(CRATES_IO_REGISTRY.into(), DOCS_RS_URL.into())].into();
         Self {
             registries,
             std: None,

src/cargo/core/compiler/standard_lib.rs

@@ -53,8 +53,7 @@ pub fn resolve_std<'cfg>(
         })
         .collect::<CargoResult<Vec<_>>>()?;
     let crates_io_url = crate::sources::CRATES_IO_INDEX.parse().unwrap();
-    let mut patch = HashMap::new();
-    patch.insert(crates_io_url, patches);
+    let patch = [(crates_io_url, patches)].into();
     let members = vec![
         String::from("library/std"),
         String::from("library/core"),

src/cargo/core/profiles.rs

@@ -139,11 +139,12 @@ impl Profiles {
 
     /// Returns the hard-coded directory names for built-in profiles.
     fn predefined_dir_names() -> HashMap<InternedString, InternedString> {
-        let mut dir_names = HashMap::new();
-        dir_names.insert(InternedString::new("dev"), InternedString::new("debug"));
-        dir_names.insert(InternedString::new("test"), InternedString::new("debug"));
-        dir_names.insert(InternedString::new("bench"), InternedString::new("release"));
-        dir_names
+        [
+            (InternedString::new("dev"), InternedString::new("debug")),
+            (InternedString::new("test"), InternedString::new("debug")),
+            (InternedString::new("bench"), InternedString::new("release")),
+        ]
+        .into()
     }
 
     /// Initialize `by_name` with the two "root" profiles, `dev`, and

src/cargo/ops/registry.rs

@@ -24,7 +24,6 @@ use crate::sources::{RegistrySource, SourceConfigMap, CRATES_IO_DOMAIN, CRATES_I
 use crate::util::config::{self, Config, SslVersionConfig, SslVersionConfigRange};
 use crate::util::errors::CargoResult;
 use crate::util::important_paths::find_root_manifest_for_wd;
-use crate::util::validate_package_name;
 use crate::util::IntoUrl;
 use crate::{drop_print, drop_println, version};
 
@@ -344,7 +343,6 @@ pub fn registry_configuration(
     // `registry.default` is handled in command-line parsing.
     let (index, token, process) = match registry {
         Some(registry) => {
-            validate_package_name(registry, "registry name", "")?;
             let index = Some(config.get_registry_index(registry)?.to_string());
             let token_key = format!("registries.{}.token", registry);
             let token = config.get_string(&token_key)?.map(|p| p.val);
@@ -418,8 +416,8 @@ fn registry(
     }
     // Parse all configuration options
     let reg_cfg = registry_configuration(config, registry.as_deref())?;
-    let opt_index = reg_cfg.index.as_ref().or_else(|| index.as_ref());
-    let sid = get_source_id(config, opt_index, registry.as_ref())?;
+    let opt_index = reg_cfg.index.as_deref().or_else(|| index.as_deref());
+    let sid = get_source_id(config, opt_index, registry.as_deref())?;
     if !sid.is_remote_registry() {
         bail!(
             "{} does not support API commands.\n\
@@ -892,11 +890,7 @@ pub fn yank(
 ///
 /// The `index` and `reg` values are from the command-line or config settings.
 /// If both are None, returns the source for crates.io.
-fn get_source_id(
-    config: &Config,
-    index: Option<&String>,
-    reg: Option<&String>,
-) -> CargoResult<SourceId> {
+fn get_source_id(config: &Config, index: Option<&str>, reg: Option<&str>) -> CargoResult<SourceId> {
     match (reg, index) {
         (Some(r), _) => SourceId::alt_registry(config, r),
         (_, Some(i)) => SourceId::for_registry(&i.into_url()?),

src/cargo/util/config/mod.rs

@@ -1053,8 +1053,7 @@ impl Config {
     }
 
     fn load_file(&self, path: &Path, includes: bool) -> CargoResult<ConfigValue> {
-        let mut seen = HashSet::new();
-        self._load_file(path, &mut seen, includes)
+        self._load_file(path, &mut HashSet::new(), includes)
     }
 
     fn _load_file(
@@ -1119,7 +1118,7 @@ impl Config {
         cv: &mut CV,
         remove: bool,
     ) -> CargoResult<Vec<(String, PathBuf, Definition)>> {
-        let abs = |path: &String, def: &Definition| -> (String, PathBuf, Definition) {
+        let abs = |path: &str, def: &Definition| -> (String, PathBuf, Definition) {
             let abs_path = match def {
                 Definition::Path(p) => p.parent().unwrap().join(&path),
                 Definition::Environment(_) | Definition::Cli => self.cwd().join(&path),
@@ -1171,9 +1170,8 @@ impl Config {
                         anyhow::format_err!("config path {:?} is not utf-8", arg_as_path)
                     })?
                     .to_string();
-                let mut map = HashMap::new();
                 let value = CV::String(str_path, Definition::Cli);
-                map.insert("include".to_string(), value);
+                let map = [("include".to_string(), value)].into();
                 CV::Table(map, Definition::Cli)
             } else {
                 // We only want to allow "dotted key" (see https://toml.io/en/v1.0.0#keys)
@@ -1253,9 +1251,8 @@ impl Config {
                 CV::from_toml(Definition::Cli, toml_v)
                     .with_context(|| format!("failed to convert --config argument `{arg}`"))?
             };
-            let mut seen = HashSet::new();
             let tmp_table = self
-                .load_includes(tmp_table, &mut seen)
+                .load_includes(tmp_table, &mut HashSet::new())
                 .with_context(|| "failed to load --config include".to_string())?;
             loaded_args
                 .merge(tmp_table, true)
@@ -1419,8 +1416,7 @@ impl Config {
 
             if let Some(token) = value_map.remove("token") {
                 if let Vacant(entry) = value_map.entry("registry".into()) {
-                    let mut map = HashMap::new();
-                    map.insert("token".into(), token);
+                    let map = [("token".into(), token)].into();
                     let table = CV::Table(map, def.clone());
                     entry.insert(table);
                 }
@@ -1994,8 +1990,7 @@ pub fn save_credentials(
 
     // Move the old token location to the new one.
     if let Some(token) = toml.as_table_mut().unwrap().remove("token") {
-        let mut map = HashMap::new();
-        map.insert("token".to_string(), token);
+        let map: HashMap<_, _> = [("token".to_string(), token)].into();
         toml.as_table_mut()
             .unwrap()
             .insert("registry".into(), map.into());
@@ -2006,13 +2001,11 @@ pub fn save_credentials(
         let (key, mut value) = {
             let key = "token".to_string();
             let value = ConfigValue::String(token, Definition::Path(file.path().to_path_buf()));
-            let mut map = HashMap::new();
-            map.insert(key, value);
+            let map = [(key, value)].into();
             let table = CV::Table(map, Definition::Path(file.path().to_path_buf()));
 
             if let Some(registry) = registry {
-                let mut map = HashMap::new();
-                map.insert(registry.to_string(), table);
+                let map = [(registry.to_string(), table)].into();
                 (
                     "registries".into(),
                     CV::Table(map, Definition::Path(file.path().to_path_buf())),

src/cargo/util/diagnostic_server.rs

@@ -75,9 +75,8 @@ impl Message {
             .shutdown(Shutdown::Write)
             .context("failed to shutdown")?;
 
-        let mut tmp = Vec::new();
         client
-            .read_to_end(&mut tmp)
+            .read_to_end(&mut Vec::new())
             .context("failed to receive a disconnect")?;
 
         Ok(())