fix(Diagnostic): remove usage of unsafe code from Infallible impl

Author: caass

src/diagnostic_impls.rs

@@ -2,45 +2,41 @@
 Default trait implementations for [`Diagnostic`].
 */
 
-use std::{convert::Infallible, fmt::Display, hint::unreachable_unchecked};
+use std::{convert::Infallible, fmt::Display};
 
 use crate::{Diagnostic, LabeledSpan, Severity, SourceCode};
 
-// Since all trait methods for [`Diagnostic`] take a reference to `self`, there must be an instance of `Self`.
-// However, since an instance of [`Infallible`] can never be constructed, these methods can never be called.
-// Therefore, these methods are unreachable, and can be safely optimized away by the compiler.
-#[allow(clippy::undocumented_unsafe_blocks)]
 impl Diagnostic for Infallible {
     fn code<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn severity(&self) -> Option<Severity> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn help<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn url<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn source_code(&self) -> Option<&dyn SourceCode> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn labels(&self) -> Option<Box<dyn Iterator<Item = LabeledSpan> + '_>> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn related<'a>(&'a self) -> Option<Box<dyn Iterator<Item = &'a dyn Diagnostic> + 'a>> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 
     fn diagnostic_source(&self) -> Option<&dyn Diagnostic> {
-        unsafe { unreachable_unchecked() }
+        match *self {}
     }
 }