chore: remove AsRef impl from the StringLiteral macro since I don't like that behavior, reorganize it to prevent leaking proc-macro2 / syn / quote

string-literal-macros-impl/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "string-literal-macros-impl"
+version = "0.1.0"
+edition = "2024"
+license.workspace = true
+
+[dependencies]
+darling = "0.23.0"
+proc-macro2 = { workspace = true }
+quote = { workspace = true }
+syn = { workspace = true }

string-literal-macros-impl/src/lib.rs

@@ -0,0 +1,71 @@
+use darling::FromDeriveInput;
+use proc_macro2::{Span, TokenStream};
+use quote::{ToTokens, quote};
+use syn::{Ident, LitStr, Path, parse_quote, parse2};
+
+#[derive(FromDeriveInput)]
+#[darling(supports(struct_unit))]
+#[darling(attributes(string_literal))]
+struct StringLiteral {
+    ident: Ident,
+    value: String,
+}
+
+impl ToTokens for StringLiteral {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Self { ident, value } = self;
+
+        let display_trait: Path = parse_quote!(::std::fmt::Display);
+        let from_trait: Path = parse_quote!(::core::convert::From);
+        let from_str_trait: Path = parse_quote!(::std::str::FromStr);
+        let result: Path = parse_quote!(::core::result::Result);
+        let wrong_literal_error_generic: Path = parse_quote!(::string_literal::WrongLiteralError);
+        let wrong_literal_error: Path = parse_quote!(#wrong_literal_error_generic<#ident>);
+        let write_macro: Path = parse_quote!(::std::write);
+
+        let value_literal = LitStr::new(value.as_str(), Span::call_site());
+
+        let output = quote! {
+            impl #from_trait<&#ident> for &'static str {
+                fn from(unit: &#ident) -> Self {
+                    #value_literal
+                }
+            }
+
+            impl #from_str_trait for #ident {
+                type Err = #wrong_literal_error;
+
+                fn from_str(s: &str) -> #result<Self, Self::Err> {
+                    if s == #value_literal {
+                        Ok(Self)
+                    } else {
+                        Err(#wrong_literal_error_generic { actual: s.to_owned(), expected: #ident })
+                    }
+                }
+            }
+
+            impl #display_trait for #ident {
+                fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                    #write_macro!(f, "state_changed")
+                }
+            }
+        };
+        dbg!(&output.to_string());
+
+        tokens.extend(output);
+    }
+}
+
+pub fn string_literal_impl(input: TokenStream) -> TokenStream {
+    let derive_input = match parse2(input) {
+        Ok(derive_input) => derive_input,
+        Err(error) => return error.into_compile_error(),
+    };
+
+    let string_literal = match StringLiteral::from_derive_input(&derive_input) {
+        Ok(string_literal) => string_literal,
+        Err(error) => return error.write_errors(),
+    };
+
+    quote! { #string_literal }
+}