contact: forbid indexing and slicing

src/contact.rs

@@ -1,5 +1,7 @@
 //! Contacts module
 
+#![forbid(clippy::indexing_slicing)]
+
 use async_std::path::PathBuf;
 use deltachat_derive::*;
 use itertools::Itertools;
@@ -1029,10 +1031,10 @@ pub fn addr_normalize(addr: &str) -> &str {
     let norm = addr.trim();
 
     if norm.starts_with("mailto:") {
-        return &norm[7..];
+        norm.get(7..).unwrap_or(norm)
+    } else {
+        norm
     }
-
-    norm
 }
 
 fn sanitize_name_and_addr(name: impl AsRef<str>, addr: impl AsRef<str>) -> (String, String) {
@@ -1042,11 +1044,15 @@ fn sanitize_name_and_addr(name: impl AsRef<str>, addr: impl AsRef<str>) -> (Stri
     if let Some(captures) = ADDR_WITH_NAME_REGEX.captures(addr.as_ref()) {
         (
             if name.as_ref().is_empty() {
-                normalize_name(&captures[1])
+                captures
+                    .get(1)
+                    .map_or("".to_string(), |m| normalize_name(m.as_str()))
             } else {
                 name.as_ref().to_string()
             },
-            captures[2].to_string(),
+            captures
+                .get(2)
+                .map_or("".to_string(), |m| m.as_str().to_string()),
         )
     } else {
         (name.as_ref().to_string(), addr.as_ref().to_string())
@@ -1117,24 +1123,17 @@ pub(crate) async fn set_profile_image(
 ///
 /// Typically, this function is not needed as it is called implicitly by `Contact::add_address_book`.
 pub fn normalize_name(full_name: impl AsRef<str>) -> String {
-    let mut full_name = full_name.as_ref().trim();
+    let full_name = full_name.as_ref().trim();
     if full_name.is_empty() {
         return full_name.into();
     }
 
-    let len = full_name.len();
-    if len > 1 {
-        let firstchar = full_name.as_bytes()[0];
-        let lastchar = full_name.as_bytes()[len - 1];
-        if firstchar == b'\'' && lastchar == b'\''
-            || firstchar == b'\"' && lastchar == b'\"'
-            || firstchar == b'<' && lastchar == b'>'
-        {
-            full_name = &full_name[1..len - 1];
-        }
+    match full_name.as_bytes() {
+        [b'\'', .., b'\''] | [b'\"', .., b'\"'] | [b'<', .., b'>'] => full_name
+            .get(1..full_name.len() - 1)
+            .map_or("".to_string(), |s| s.trim().into()),
+        _ => full_name.to_string(),
     }
-
-    full_name.trim().into()
 }
 
 fn cat_fingerprint(