Implement FromIterator for RootCertStore (#1708)

Co-authored-by: Daniel McCarney <daniel@binaryparadox.net>

examples/src/bin/limitedclient.rs

@@ -8,8 +8,7 @@ use std::net::TcpStream;
 use std::sync::Arc;
 
 fn main() {
-    let mut root_store = rustls::RootCertStore::empty();
-    root_store.extend(
+    let root_store = rustls::RootCertStore::from_iter(
         webpki_roots::TLS_SERVER_ROOTS
             .iter()
             .cloned(),

examples/src/bin/simple_0rtt_client.rs

@@ -66,8 +66,7 @@ fn start_connection(config: &Arc<rustls::ClientConfig>, domain_name: &str) {
 fn main() {
     env_logger::init();
 
-    let mut root_store = RootCertStore::empty();
-    root_store.extend(
+    let root_store = RootCertStore::from_iter(
         webpki_roots::TLS_SERVER_ROOTS
             .iter()
             .cloned(),

examples/src/bin/simpleclient.rs

@@ -15,8 +15,7 @@ use std::sync::Arc;
 use rustls::RootCertStore;
 
 fn main() {
-    let mut root_store = RootCertStore::empty();
-    root_store.extend(
+    let root_store = RootCertStore::from_iter(
         webpki_roots::TLS_SERVER_ROOTS
             .iter()
             .cloned(),

provider-example/examples/client.rs

@@ -5,8 +5,7 @@ use std::sync::Arc;
 fn main() {
     env_logger::init();
 
-    let mut root_store = rustls::RootCertStore::empty();
-    root_store.extend(
+    let root_store = rustls::RootCertStore::from_iter(
         webpki_roots::TLS_SERVER_ROOTS
             .iter()
             .cloned(),

rustls/src/lib.rs

@@ -116,11 +116,10 @@
 //!
 //! ```rust,no_run
 //! # #[cfg(feature = "ring")] {
-//! let mut root_store = rustls::RootCertStore::empty();
-//! root_store.extend(
+//! let root_store = rustls::RootCertStore::from_iter(
 //!     webpki_roots::TLS_SERVER_ROOTS
 //!         .iter()
-//!         .cloned()
+//!         .cloned(),
 //! );
 //! # }
 //! ```
@@ -147,11 +146,10 @@
 //! # use rustls;
 //! # use webpki;
 //! # use std::sync::Arc;
-//! # let mut root_store = rustls::RootCertStore::empty();
-//! # root_store.extend(
+//! # let root_store = rustls::RootCertStore::from_iter(
 //! #  webpki_roots::TLS_SERVER_ROOTS
 //! #      .iter()
-//! #      .cloned()
+//! #      .cloned(),
 //! # );
 //! # let config = rustls::ClientConfig::builder()
 //! #     .with_root_certificates(root_store)

rustls/src/webpki/anchors.rs

@@ -103,6 +103,14 @@ impl RootCertStore {
     }
 }
 
+impl FromIterator<TrustAnchor<'static>> for RootCertStore {
+    fn from_iter<T: IntoIterator<Item = TrustAnchor<'static>>>(iter: T) -> Self {
+        Self {
+            roots: iter.into_iter().collect(),
+        }
+    }
+}
+
 impl Extend<TrustAnchor<'static>> for RootCertStore {
     fn extend<T: IntoIterator<Item = TrustAnchor<'static>>>(&mut self, iter: T) {
         self.roots.extend(iter);
@@ -122,13 +130,12 @@ fn root_cert_store_debug() {
     use core::iter;
     use pki_types::Der;
 
-    let mut store = RootCertStore::empty();
     let ta = TrustAnchor {
         subject: Der::from_slice(&[]),
         subject_public_key_info: Der::from_slice(&[]),
         name_constraints: None,
     };
-    store.extend(iter::repeat(ta).take(138));
+    let store = RootCertStore::from_iter(iter::repeat(ta).take(138));
 
     assert_eq!(
         format!("{:?}", store),