feat(build): emit checked param tokens

Generate ParamName constants for handle data parameters so public code can refer to checked param metadata instead of stringly typed names.

req: codegen/003

slhx-core/src/lib.rs

@@ -186,6 +186,35 @@ impl core::fmt::Display for CssClass {
     }
 }
 
+/// A generated, checked parameter token.
+/// req: codegen/003
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub struct ParamName {
+    name: &'static str,
+}
+
+impl ParamName {
+    pub const fn new(name: &'static str) -> Self {
+        Self { name }
+    }
+
+    pub const fn as_str(self) -> &'static str {
+        self.name
+    }
+}
+
+impl AsRef<str> for ParamName {
+    fn as_ref(&self) -> &str {
+        self.name
+    }
+}
+
+impl core::fmt::Display for ParamName {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.name)
+    }
+}
+
 /// A generated, checked component token.
 /// req: component/003
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]

slhx-core/tests/effect_batch.rs

@@ -1,7 +1,7 @@
 use slhx_core::{
     event, navigate, redirect, replace, Atom, AtomSnapshot, AtomState, BuildFingerprint,
     ComponentRef, CssClass, CssClasses, Effect, EffectBatch, Form, Handle, IntoEffect, KeyedSlot,
-    NavigateMode, Payload, ResourceKind, SafeHtml, ScopeKey, Slot,
+    NavigateMode, ParamName, Payload, ResourceKind, SafeHtml, ScopeKey, Slot,
 };
 
 #[test]
@@ -93,6 +93,14 @@ fn slot_html_requires_explicit_safe_html() {
     assert_eq!(payload, Payload::Html(String::from("<strong>ok</strong>")));
 }
 
+#[test]
+fn param_names_format_generated_param_names() {
+    // req: codegen/003
+    let param = ParamName::new("todo_id");
+    assert_eq!(param.as_str(), "todo_id");
+    assert_eq!(param.to_string(), "todo_id");
+}
+
 #[test]
 fn component_refs_format_generated_component_names() {
     // req: component/003