cleanup and add some new methods

src/lib.rs

@@ -1,4 +1,4 @@
-#![allow(unknown_lints)] // `warn(rustdoc::all)` triggers this for weird nightly reasons
+#![allow(unknown_lints)] // `warn(rustdoc::all)` triggers this for some reason
 #![warn(rustdoc::all)]
 #![warn(clippy::all)]
 #![warn(clippy::pedantic)]
@@ -21,14 +21,17 @@ use std::{
 
 /// A smaller [`Cow<'static, str>`](Cow).
 ///
-/// This type can represent either an [`&'static str`](prim@str), or a [`String`], and fits within 3 words
-/// (the same size as `String`). It does this by storing a capacity of `0` when it is borrowed.
-/// However, this does mean that it is impossible to distinguish between borrowed and owned when
-/// `capacity == len == 0`, but in that case it really doesn't matter much anyway since an owned
-/// `String` with capacity equal to zero has not yet allocated.
+/// This type can represent either an [`&'static str`](prim@str), or a [`String`], and fits within
+/// 3 words (the same size as `String`). It does this by storing a capacity of `0` when it is
+/// borrowed. However, this does mean that it is impossible to distinguish between borrowed and
+/// owned when `capacity == len == 0`, but in that case it really doesn't matter much anyway since
+/// an owned `String` with capacity equal to zero has not yet allocated.
 ///
-/// When doing non-mutating actions such as [`Deref::deref`], the string remains in whatever state it
-/// was in. When doing mutating actions such as [`DerefMut::deref_mut`], the string becomes owned.
+/// Note that this method of distinguishing a borrowed string from an owned string still allows
+/// storing a [`NonNull`] pointer, So this type is *still* 3 words when in an [`Option`].
+///
+/// When doing non-mutating actions such as [`Deref::deref`], the string remains in whatever state
+/// it was in. When doing mutating actions such as [`DerefMut::deref_mut`], the string is made owned.
 ///
 /// ## Mutation as a `String`
 ///
@@ -149,13 +152,9 @@ impl Stringish {
     /// If the `Stringish` is borrowed, the data is copied into a new allocation and the
     /// `Stringish` becomes owned. Otherwise, nothing happens.
     pub fn make_owned(&mut self) {
-        if let None | Some(true) = self.is_owned() {
-            return;
+        if let Some(s) = self.as_static_str() {
+            *self = Stringish::new_owned(String::from(s));
         }
-
-        let mut s = String::with_capacity(self.len);
-        s.push_str(self);
-        *self = Stringish::new_owned(s);
     }
 
     /// Converts a `Stringish` into an owned [`String`].
@@ -171,7 +170,48 @@ impl Stringish {
         unsafe { String::from_raw_parts(this.ptr.as_ptr(), this.len, this.cap) }
     }
 
-    // Reborrowing
+    /// Returns the inner [`&'static str`](prim@str) if the `Stringish` is borrowed.
+    #[must_use]
+    pub fn as_static_str(&self) -> Option<&'static str> {
+        if let None | Some(true) = self.is_borrowed() {
+            // SAFETY: if we are borrowed then we borrow a `&'static str`, so lifetime extension is safe
+            Some(unsafe { &*(self.as_str() as *const str) })
+        } else {
+            None
+        }
+    }
+
+    /// Converts the `Stringish` into a [`Cow<'static, str>`](Cow).
+    ///
+    /// This is the inverse of [`Stringish::from_cow`]
+    #[must_use]
+    pub fn into_cow(self) -> Cow<'static, str> {
+        if let Some(s) = self.as_static_str() {
+            Cow::Borrowed(s)
+        } else {
+            Cow::Owned(self.into_owned())
+        }
+    }
+
+    /// Consumes and leaks the `Stringish`, returning an immutable reference to the contents.
+    ///
+    /// If the `Stringish` is borrowed, no allocation needs to be created since it already contains
+    /// a [`&'static str`](prim@str).
+    ///
+    /// If you wish to get a mutable reference, see [`String::leak`].
+    #[must_use]
+    pub fn leak(self) -> &'static str {
+        if let Some(s) = self.as_static_str() {
+            s
+        } else {
+            // SAFETY: workaround for `String::leak` being unstable
+            unsafe { str::from_utf8_unchecked(self.into_owned().into_bytes().leak()) }
+        }
+    }
+
+    /////////////////
+    // Reborrowing //
+    /////////////////
 
     /// Returns a byte slice of this `Stringish`'s contents.
     #[must_use]
@@ -239,6 +279,15 @@ impl From<Cow<'static, str>> for Stringish {
     }
 }
 
+/// Converts a `Stringish` into a [`Cow<'static, str>`](Cow).
+///
+/// See also: [`Stringish::into_cow`]
+impl From<Stringish> for Cow<'static, str> {
+    fn from(stringish: Stringish) -> Self {
+        stringish.into_cow()
+    }
+}
+
 impl Deref for Stringish {
     type Target = str;
 
@@ -254,7 +303,9 @@ impl DerefMut for Stringish {
 }
 
 impl Stringish {
-    // Mutation as a `String`
+    ////////////////////////////
+    // Mutation as a `String` //
+    ////////////////////////////
 
     /// Allows mutation of this `Stringish` as a `String` using a guard.
     ///