docs: improve and add missing doc comment

Author: ryota2357

src/errors/from_utf16_error.rs

@@ -1,5 +1,9 @@
 use core::{error::Error, fmt};
 
+/// An error if the conversion from a sequence of UTF-16 code units to a [`LeanString`] fails due
+/// to invalid UTF-16 code unit sequences.
+///
+/// [`LeanString`]: crate::LeanString
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct FromUtf16Error;
 

src/errors/reserve_error.rs

@@ -1,6 +1,6 @@
 use core::{error::Error, fmt};
 
-/// A possible error value if allocating or resizing a [`LeanString`] failed.
+/// An error if allocating or resizing a [`LeanString`] failed.
 ///
 /// [`LeanString`]: crate::LeanString
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]

src/errors/to_lean_string_error.rs

@@ -2,9 +2,17 @@ use core::{error::Error, fmt};
 
 use super::ReserveError;
 
+/// An error that can occur when converting a value to a [`LeanString`].
+///
+/// This error can be caused by either a reserve error when allocating memory,
+/// or a formatting error when converting the value to a string.
+///
+/// [`LeanString`]: crate::LeanString
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum ToLeanStringError {
+    /// An error occurred while trying to allocate memory.
     Reserve(ReserveError),
+    /// A formatting error occurred during conversion.
     Fmt(fmt::Error),
 }
 

src/lib.rs

@@ -32,6 +32,7 @@ pub use traits::ToLeanString;
 
 mod features;
 
+/// Compact, clone-on-write, UTF-8 encoded, growable string type.
 #[repr(transparent)]
 pub struct LeanString(Repr);
 
@@ -123,8 +124,8 @@ impl LeanString {
 
     /// Fallible version of [`LeanString::with_capacity()`].
     ///
-    /// This method won't panic if the system is out-of-memory, or the `capacity` is too large, but
-    /// return an [`ReserveError`]. Otherwise it behaves the same as [`LeanString::with_capacity()`].
+    /// This method won't panic if the system is out of memory, or if the `capacity` is too large, but
+    /// returns a [`ReserveError`]. Otherwise it behaves the same as [`LeanString::with_capacity()`].
     #[inline]
     pub fn try_with_capacity(capacity: usize) -> Result<Self, ReserveError> {
         Repr::with_capacity(capacity).map(LeanString)

src/traits.rs

@@ -5,10 +5,22 @@ use core::{fmt, fmt::Write, num::NonZero};
 
 /// A trait for converting a value to a [`LeanString`].
 pub trait ToLeanString {
+    /// Converts the value to a [`LeanString`].
+    ///
+    /// # Panics
+    ///
+    /// Panics if conversion fails. For a non-panicking version, use [`try_to_lean_string`].
+    ///
+    /// [`try_to_lean_string`]: Self::try_to_lean_string
     fn to_lean_string(&self) -> LeanString {
         self.try_to_lean_string().unwrap_with_msg()
     }
 
+    /// Attempts to convert the value to a [`LeanString`].
+    ///
+    /// # Errors
+    ///
+    /// Returns a [`ToLeanStringError`] if the conversion fails.
     fn try_to_lean_string(&self) -> Result<LeanString, ToLeanStringError>;
 }