convenient infallible unwrapper

Author: functora

rust/functora-tagged/README.md

@@ -88,17 +88,18 @@ When a `Tag` type has a default `Refine` implementation that doesn't add new con
 
 ```rust
 use functora_tagged::*;
+use std::convert::Infallible;
 
 pub enum NonNegTag {}
 
 impl Refine<usize> for NonNegTag {
-    type RefineError = ();
+    type RefineError = Infallible;
 }
 
 pub type NonNeg = Tagged<usize, NonNegTag>;
 
 let rep = 123;
-let new = NonNeg::new(rep).unwrap();
+let new = NonNeg::new(rep).infallible();
 
 assert_eq!(*new.rep(), rep);
 ```

rust/functora-tagged/src/infallible.rs

@@ -0,0 +1,11 @@
+use std::convert::Infallible;
+
+pub trait InfallibleInto<T> {
+    fn infallible(self) -> T;
+}
+
+impl<T> InfallibleInto<T> for Result<T, Infallible> {
+    fn infallible(self) -> T {
+        self.unwrap()
+    }
+}

rust/functora-tagged/src/lib.rs

@@ -6,6 +6,8 @@ use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
 use std::ops::Deref;
 use std::str::FromStr;
+pub mod infallible;
+pub use infallible::*;
 
 #[derive(Debug)]
 pub struct Tagged<Rep, Tag>(Rep, PhantomData<Tag>);

rust/functora-tagged/tests/integration.rs

@@ -1,7 +1,10 @@
 use derive_more::Display;
-use functora_tagged::{ParseError, Refine, Tagged};
+use functora_tagged::{
+    InfallibleInto, ParseError, Refine, Tagged,
+};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+use std::convert::Infallible;
 use std::error::Error;
 use std::fmt::Debug;
 
@@ -17,6 +20,10 @@ pub type UserId = Tagged<NonEmpty<String>, UserIdTag>;
 pub enum EmailTag {}
 pub type Email = Tagged<NonEmpty<String>, EmailTag>;
 
+#[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Debug)]
+pub enum UpperTag {}
+pub type UpperString = Tagged<String, UpperTag>;
+
 #[derive(
     Eq, PartialEq, Ord, PartialOrd, Clone, Debug, Display,
 )]
@@ -76,6 +83,15 @@ impl Refine<NonEmpty<String>> for EmailTag {
     }
 }
 
+impl Refine<String> for UpperTag {
+    type RefineError = Infallible;
+    fn refine(
+        rep: String,
+    ) -> Result<String, Self::RefineError> {
+        Ok(rep.to_uppercase())
+    }
+}
+
 #[test]
 fn test_non_empty_from_str_success() {
     let ne: NonEmpty<String> = "hello".parse().unwrap();
@@ -154,6 +170,13 @@ fn test_tagged_clone_debug() {
     assert!(dbg.contains("PhantomData"));
 }
 
+#[test]
+fn test_upper_string_infallible() {
+    let tagged: UpperString =
+        UpperString::new("test".into()).infallible();
+    assert_eq!(tagged.rep(), "TEST");
+}
+
 #[cfg(feature = "serde")]
 #[test]
 fn test_serde_user_id_roundtrip() {