Fix FromMeta for chars (#126)

* Fix FromMeta for char
* Get rid of unwrap in from_string impl for char

Co-authored-by: Veetaha <[email protected]>
Co-authored-by: Oleksandr Kryvytskyi <[email protected]>

core/src/from_meta.rs

@@ -25,6 +25,10 @@ use {Error, Result};
 /// * As a boolean literal, e.g. `foo = true`.
 /// * As a string literal, e.g. `foo = "true"`.
 ///
+/// ## char
+/// * As a char literal, e.g. `foo = '#'`.
+/// * As a string literal consisting of a single character, e.g. `foo = "#"`.
+///
 /// ## String
 /// * As a string literal, e.g. `foo = "hello"`.
 /// * As a raw string literal, e.g. `foo = r#"hello "world""#`.
@@ -98,6 +102,7 @@ pub trait FromMeta: Sized {
         (match *value {
             Lit::Bool(ref b) => Self::from_bool(b.value),
             Lit::Str(ref s) => Self::from_string(&s.value()),
+            Lit::Char(ref ch) => Self::from_char(ch.value()),
             _ => Err(Error::unexpected_lit_type(value)),
         })
         .map_err(|e| e.with_span(value))
@@ -152,6 +157,24 @@ impl FromMeta for AtomicBool {
     }
 }
 
+impl FromMeta for char {
+    fn from_char(value: char) -> Result<Self> {
+        Ok(value)
+    }
+
+    fn from_string(s: &str) -> Result<Self> {
+        let mut chars = s.chars();
+        let char1 = chars.next();
+        let char2 = chars.next();
+
+        if let (Some(char), None) = (char1, char2) {
+            Ok(char)
+        } else {
+            Err(Error::unexpected_type("string"))
+        }
+    }
+}
+
 impl FromMeta for String {
     fn from_string(s: &str) -> Result<Self> {
         Ok(s.to_string())
@@ -595,6 +618,15 @@ mod tests {
         assert_eq!(fm::<bool>(quote!(ignore = "false")), false);
     }
 
+    #[test]
+    fn char_succeeds() {
+        // char literal
+        assert_eq!(fm::<char>(quote!(ignore = '😬')), '😬');
+
+        // string literal
+        assert_eq!(fm::<char>(quote!(ignore = "😬")), '😬');
+    }
+
     #[test]
     fn string_succeeds() {
         // cooked form