chore: checkpoint before Python removal

vendor/iri-string/src/spec/internal.rs

@@ -0,0 +1,58 @@
+//! A private module for sealed trait and internal implementations.
+//!
+//! Note that this MUST be a private module.
+//! See [Rust API Guidelines][sealed-trait] about the necessity of being private.
+//!
+//! [sealed-trait]:
+//! https://rust-lang.github.io/api-guidelines/future-proofing.html#sealed-traits-protect-against-downstream-implementations-c-sealed
+
+use crate::parser::char::is_ucschar;
+use crate::spec::{IriSpec, UriSpec};
+
+/// A trait to prohibit user-defined types from implementing `Spec`.
+///
+/// About sealed trait, see [Rust API Guidelines][future-proofing].
+///
+/// [future-proofing]: https://rust-lang.github.io/api-guidelines/future-proofing.html
+pub trait Sealed: SpecInternal {}
+
+impl Sealed for IriSpec {}
+impl Sealed for UriSpec {}
+
+/// Internal implementations for spec types.
+pub trait SpecInternal: Sized {
+    /// Checks if the given non-ASCII character matches `unreserved` or `iunreserved` rule.
+    #[must_use]
+    fn is_nonascii_char_unreserved(c: char) -> bool;
+    /// Checks if the given character matches `iprivate` rule.
+    #[must_use]
+    fn is_nonascii_char_private(c: char) -> bool;
+}
+
+impl SpecInternal for IriSpec {
+    #[inline]
+    fn is_nonascii_char_unreserved(c: char) -> bool {
+        is_ucschar(c)
+    }
+
+    fn is_nonascii_char_private(c: char) -> bool {
+        matches!(
+            u32::from(c),
+            0xE000..=0xF8FF |
+            0xF_0000..=0xF_FFFD |
+            0x10_0000..=0x10_FFFD
+        )
+    }
+}
+
+impl SpecInternal for UriSpec {
+    #[inline]
+    fn is_nonascii_char_unreserved(_: char) -> bool {
+        false
+    }
+
+    #[inline]
+    fn is_nonascii_char_private(_: char) -> bool {
+        false
+    }
+}