Match crate and slug names

compiler/rustc_middle/src/error.rs

@@ -64,3 +64,11 @@ pub(crate) struct StrictCoherenceNeedsNegativeCoherence {
     #[label]
     pub attr_span: Option<Span>,
 }
+
+#[derive(Diagnostic)]
+#[diag(middle_const_not_used_in_type_alias)]
+pub(super) struct ConstNotUsedTraitAlias {
+    pub ct: String,
+    #[primary_span]
+    pub span: Span,
+}