Minor fixes (#87)

* Move multipart classification into own closure

* Add classification enum

* Express classification indirectly with an enum

* Express logic clause in equivalent way, add assert inline test to make sure of it

* Remove old classifier

* Remove enum indirection

* Remove closure

* Hoist common if condition into outer scope

* Simplify expression

* Simplify lifetime bounds

A missing lifetime in the GetHeader trait was inferred by lifetime elision rules
to be shorter than necessary, leading to awkward lifetime constraints being
propagated throughout many functions that didnt need them.

* Prohibit Rust 2018 idioms, return longest feasible lifetimes

* Dont duplicate crlf in extension when saving failing results

src/core/address.rs

@@ -73,7 +73,7 @@ impl<'x> Address<'x> {
     }
 
     /// Returns an iterator over the addresses in the list, or the addresses in the groups.
-    pub fn iter<'y: 'x>(&'y self) -> Box<dyn DoubleEndedIterator<Item = &Addr<'x>> + 'x> {
+    pub fn iter(&self) -> Box<dyn DoubleEndedIterator<Item = &Addr<'x>> + '_> {
         match self {
             Address::List(list) => Box::new(list.iter()),
             Address::Group(group) => {

src/core/header.rs

@@ -26,7 +26,7 @@ impl<'x> Header<'x> {
     }
 
     /// Returns the parsed header value
-    pub fn value(&self) -> &HeaderValue {
+    pub fn value(&self) -> &HeaderValue<'x> {
         &self.value
     }
 
@@ -171,14 +171,14 @@ impl<'x> HeaderValue<'x> {
         }
     }
 
-    pub fn as_received(&self) -> Option<&Received> {
+    pub fn as_received(&self) -> Option<&Received<'x>> {
         match *self {
             HeaderValue::Received(ref r) => Some(r),
             _ => None,
         }
     }
 
-    pub fn as_content_type(&self) -> Option<&ContentType> {
+    pub fn as_content_type(&self) -> Option<&ContentType<'x>> {
         match *self {
             HeaderValue::ContentType(ref c) => Some(c),
             _ => None,
@@ -374,7 +374,7 @@ impl<'x> HeaderName<'x> {
         }
     }
 
-    pub fn as_str<'y: 'x>(&'y self) -> &'x str {
+    pub fn as_str(&self) -> &str {
         match self {
             HeaderName::Other(other) => other.as_ref(),
             _ => self.as_static_str(),
@@ -542,7 +542,7 @@ impl<'x> MimeHeaders<'x> for Message<'x> {
             .and_then(|header| header.as_text())
     }
 
-    fn content_disposition(&self) -> Option<&ContentType> {
+    fn content_disposition(&self) -> Option<&ContentType<'x>> {
         self.parts[0]
             .headers
             .header_value(&HeaderName::ContentDisposition)
@@ -563,14 +563,14 @@ impl<'x> MimeHeaders<'x> for Message<'x> {
             .and_then(|header| header.as_text())
     }
 
-    fn content_type(&self) -> Option<&ContentType> {
+    fn content_type(&self) -> Option<&ContentType<'x>> {
         self.parts[0]
             .headers
             .header_value(&HeaderName::ContentType)
             .and_then(|header| header.as_content_type())
     }
 
-    fn content_language(&self) -> &HeaderValue {
+    fn content_language(&self) -> &HeaderValue<'x> {
         self.parts[0]
             .headers
             .header_value(&HeaderName::ContentLanguage)
@@ -667,7 +667,7 @@ impl<'x> MessagePart<'x> {
     }
 
     /// Get the message headers
-    pub fn headers(&self) -> &[Header] {
+    pub fn headers(&self) -> &[Header<'x>] {
         &self.headers
     }
 
@@ -713,7 +713,7 @@ impl<'x> MessagePart<'x> {
 }
 
 impl<'x> fmt::Display for MessagePart<'x> {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt.write_str(self.text_contents().unwrap_or("[no contents]"))
     }
 }
@@ -725,7 +725,7 @@ impl<'x> MimeHeaders<'x> for MessagePart<'x> {
             .and_then(|header| header.as_text())
     }
 
-    fn content_disposition(&self) -> Option<&ContentType> {
+    fn content_disposition(&self) -> Option<&ContentType<'x>> {
         self.headers
             .header_value(&HeaderName::ContentDisposition)
             .and_then(|header| header.as_content_type())
@@ -743,13 +743,13 @@ impl<'x> MimeHeaders<'x> for MessagePart<'x> {
             .and_then(|header| header.as_text())
     }
 
-    fn content_type(&self) -> Option<&ContentType> {
+    fn content_type(&self) -> Option<&ContentType<'x>> {
         self.headers
             .header_value(&HeaderName::ContentType)
             .and_then(|header| header.as_content_type())
     }
 
-    fn content_language(&self) -> &HeaderValue {
+    fn content_language(&self) -> &HeaderValue<'x> {
         self.headers
             .header_value(&HeaderName::ContentLanguage)
             .unwrap_or(&HeaderValue::Empty)
@@ -786,7 +786,7 @@ impl<'x> ContentType<'x> {
     }
 
     /// Removes an attribute by name
-    pub fn remove_attribute(&mut self, name: &str) -> Option<Cow<str>> {
+    pub fn remove_attribute(&mut self, name: &str) -> Option<Cow<'x, str>> {
         let attributes = self.attributes.as_mut()?;
 
         attributes
@@ -796,15 +796,15 @@ impl<'x> ContentType<'x> {
     }
 
     /// Returns all attributes
-    pub fn attributes(&self) -> Option<&[(Cow<str>, Cow<str>)]> {
+    pub fn attributes(&self) -> Option<&[(Cow<'x, str>, Cow<'x, str>)]> {
         self.attributes.as_deref()
     }
 
     /// Returns `true` when the provided attribute name is present
     pub fn has_attribute(&self, name: &str) -> bool {
         self.attributes
             .as_ref()
-            .map_or_else(|| false, |attr| attr.iter().any(|(key, _)| key == name))
+            .map_or(false, |attr| attr.iter().any(|(key, _)| key == name))
     }
 
     /// Returns ```true``` if the Content-Disposition type is "attachment"
@@ -840,7 +840,7 @@ impl<'x> Received<'x> {
     }
 
     /// Returns the hostname or IP address of the machine that originated the message
-    pub fn from(&self) -> Option<&Host> {
+    pub fn from(&self) -> Option<&Host<'x>> {
         self.from.as_ref()
     }
 
@@ -855,7 +855,7 @@ impl<'x> Received<'x> {
     }
 
     /// Returns the hostname or IP address of the machine that received the message
-    pub fn by(&self) -> Option<&Host> {
+    pub fn by(&self) -> Option<&Host<'x>> {
         self.by.as_ref()
     }
 
@@ -890,7 +890,7 @@ impl<'x> Received<'x> {
     }
 
     /// Returns the EHLO/LHLO/HELO hostname or IP address of the machine that sent the message
-    pub fn helo(&self) -> Option<&Host> {
+    pub fn helo(&self) -> Option<&Host<'x>> {
         self.helo.as_ref()
     }
 
@@ -921,14 +921,14 @@ impl<'x> Host<'x> {
 }
 
 impl<'x> GetHeader<'x> for Vec<Header<'x>> {
-    fn header_value(&self, name: &HeaderName) -> Option<&HeaderValue<'x>> {
+    fn header_value(&self, name: &HeaderName<'_>) -> Option<&HeaderValue<'x>> {
         self.iter()
             .rev()
             .find(|header| &header.name == name)
             .map(|header| &header.value)
     }
 
-    fn header(&self, name: impl Into<HeaderName<'x>>) -> Option<&Header> {
+    fn header(&self, name: impl Into<HeaderName<'x>>) -> Option<&Header<'x>> {
         let name = name.into();
         self.iter().rev().find(|header| header.name == name)
     }
@@ -953,7 +953,7 @@ impl<'x> From<String> for HeaderName<'x> {
 }
 
 impl From<HeaderName<'_>> for String {
-    fn from(header: HeaderName) -> Self {
+    fn from(header: HeaderName<'_>) -> Self {
         header.to_string()
     }
 }