units: Fix `missing_errors_doc` clippy lint

Change the lint to `warn` in `units/Cargo.toml`.
Allow `missing_errors_doc` in `amount/serde.rs` and `fee_rate/serde.rs`.
Add missing `# Errors` sections to rustdocs where the lint gives a
warning.

units/Cargo.toml

@@ -105,7 +105,7 @@ match_wild_err_arm = "warn"
 match_wildcard_for_single_variants = "warn"
 maybe_infinite_iter = "warn"
 mismatching_type_param_order = "warn"
-missing_errors_doc = "allow" # TODO: Still needs considering.
+missing_errors_doc = "warn"
 missing_fields_in_debug = "warn"
 missing_panics_doc = "allow" # TODO: Still needs considering.
 must_use_candidate = "allow" # Useful for audit but many false positives.

units/src/amount/serde.rs

@@ -2,6 +2,7 @@
 
 // methods are implementation of a standardized serde-specific signature
 #![allow(missing_docs)]
+#![allow(clippy::missing_errors_doc)]
 
 //! This module adds serde serialization and deserialization support for amounts.
 //!

units/src/fee_rate/serde.rs

@@ -3,6 +3,7 @@
 // Module implements standardized serde-specific trait methods.
 #![allow(missing_docs)]
 #![allow(clippy::trivially_copy_pass_by_ref)]
+#![allow(clippy::missing_errors_doc)]
 
 //! This module adds serde serialization and deserialization support for amounts.
 //!

units/src/locktime/absolute.rs

@@ -41,6 +41,10 @@ impl Height {
     /// Constructs a new [`Height`] from a hex string.
     ///
     /// The input string may or may not contain a typical hex prefix e.g., `0x`.
+    ///
+    /// # Errors
+    ///
+    /// If the input string is not a valid hex representation of a block height.
     pub fn from_hex(s: &str) -> Result<Self, ParseHeightError> {
         parse_hex(s, Self::from_consensus)
     }
@@ -139,6 +143,10 @@ impl Time {
     /// Constructs a new [`Time`] from a hex string.
     ///
     /// The input string may or may not contain a typical hex prefix e.g., `0x`.
+    ///
+    /// # Errors
+    ///
+    /// If the input string is not a valid hex representation of a block time.
     pub fn from_hex(s: &str) -> Result<Self, ParseTimeError> { parse_hex(s, Self::from_consensus) }
 
     /// Constructs a new block time.

units/src/parse.rs

@@ -76,22 +76,29 @@ mod sealed {
 
 /// Parses the input string as an integer returning an error carrying rich context.
 ///
-/// On error this function allocates to copy the input string into the error return. If the caller
-/// has a `String` or `Box<str>` which is not used later it's better to call
+/// If the caller has a `String` or `Box<str>` which is not used later it's better to call
 /// [`parse::int_from_string`] or [`parse::int_from_box`] respectively.
 ///
 /// [`parse::int_from_string`]: crate::parse::int_from_string
 /// [`parse::int_from_box`]: crate::parse::int_from_box
+///
+/// # Errors
+///
+/// On error this function allocates to copy the input string into the error return.
 pub fn int_from_str<T: Integer>(s: &str) -> Result<T, ParseIntError> { int(s) }
 
 /// Parses the input string as an integer returning an error carrying rich context.
 ///
+/// # Errors
+///
 /// On error the input string is moved into the error return without allocating.
 #[cfg(feature = "alloc")]
 pub fn int_from_string<T: Integer>(s: alloc::string::String) -> Result<T, ParseIntError> { int(s) }
 
 /// Parses the input string as an integer returning an error carrying rich context.
 ///
+/// # Errors
+///
 /// On error the input string is converted into the error return without allocating.
 #[cfg(feature = "alloc")]
 pub fn int_from_box<T: Integer>(s: alloc::boxed::Box<str>) -> Result<T, ParseIntError> { int(s) }