Add ISO 8601 parser for duration format with designators

src/calendar_duration.rs

@@ -1,7 +1,9 @@
 use core::fmt;
 use core::num::NonZeroU64;
+use core::str;
 use core::time::Duration;
 
+use crate::format::{parse_iso8601_duration, ParseError, TOO_LONG};
 use crate::{expect, try_opt};
 
 /// ISO 8601 duration type.
@@ -114,6 +116,18 @@ impl fmt::Display for CalendarDuration {
     }
 }
 
+impl str::FromStr for CalendarDuration {
+    type Err = ParseError;
+
+    fn from_str(s: &str) -> Result<CalendarDuration, ParseError> {
+        let (s, duration) = parse_iso8601_duration(s)?;
+        if !s.is_empty() {
+            return Err(TOO_LONG);
+        }
+        Ok(duration)
+    }
+}
+
 impl CalendarDuration {
     /// Create a new duration initialized to `0`.
     ///

src/format/mod.rs

@@ -68,6 +68,7 @@ pub use formatting::{format, format_item, DelayedFormat};
 pub use locales::Locale;
 pub(crate) use parse::parse_rfc3339;
 pub use parse::{parse, parse_and_remainder};
+pub(crate) use parse_iso8601::parse_iso8601_duration;
 pub use parsed::Parsed;
 pub use strftime::StrftimeItems;