Merge #44

44: Scope trait TextLen just for primitives r=matklad a=CAD97

As an alternative to #41 

I thought I posted this already....

Co-authored-by: CAD97 <[email protected]>

Author: bors[bot]

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "text-size"
-version = "0.99.0"
+version = "1.0.0-pre.1"
 edition = "2018"
 
 authors = [

src/traits.rs

@@ -3,26 +3,34 @@ use {
     std::{borrow::Cow, convert::TryInto, rc::Rc, sync::Arc},
 };
 
-/// Text-like structures that have a text size.
-pub trait TextLen: Copy {
-    /// The size of this text-alike.
+use priv_in_pub::Sealed;
+mod priv_in_pub {
+    pub trait Sealed {}
+}
+
+/// Primitives with a textual length that can be passed to [`TextSize::of`].
+pub trait TextLen: Copy + Sealed {
+    /// The textual length of this primitive.
     fn text_len(self) -> TextSize;
 }
 
+impl Sealed for &'_ str {}
 impl TextLen for &'_ str {
     #[inline]
     fn text_len(self) -> TextSize {
         self.len().try_into().unwrap()
     }
 }
 
+impl Sealed for char {}
 impl TextLen for char {
     #[inline]
     fn text_len(self) -> TextSize {
         (self.len_utf8() as u32).into()
     }
 }
 
+impl<D> Sealed for &'_ D where D: TextLen + Copy {}
 impl<D> TextLen for &'_ D
 where
     D: TextLen + Copy,
@@ -38,6 +46,7 @@ where
 // open a PR and we are likely to accept it. Or convince Rust to deref to &str.
 macro_rules! impl_textlen_for_string {
     ($($ty:ty),+ $(,)?) => {$(
+        impl Sealed for $ty {}
         impl TextLen for $ty {
             #[inline]
             fn text_len(self) -> TextSize {

tests/constructors.rs

@@ -6,7 +6,7 @@ use {
 #[derive(Copy, Clone)]
 struct BadRope<'a>(&'a [&'a str]);
 
-impl TextLen for BadRope<'_> {
+impl BadRope<'_> {
     fn text_len(self) -> TextSize {
         self.0.iter().map(TextSize::of).sum()
     }
@@ -29,6 +29,7 @@ fn main() {
         &String::new().into_boxed_str(),
         &Arc::new(String::new()),
         &Cow::Borrowed(""),
-        BadRope(&[""]),
     }
+
+    let _ = BadRope(&[""]).text_len();
 }