1 files changed, 80 insertions, 0 deletions
diff --git a/src/code.rs b/src/code.rs
new file mode 100644
index 0000000..22dc795
--- /dev/null
+++ b/src/code.rs
@@ -0,0 +1,80 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+    utils::gen_all_variants_with,
+};
+
+#[derive(Debug)]
+pub struct Code(pub String);
+
+impl Parse for Code {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "code" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                let la = content.lookahead1();
+                if la.peek(syn::LitStr) {
+                    let str = content.parse::<syn::LitStr>()?;
+                    Ok(Code(str.value()))
+                } else {
+                    let path = content.parse::<syn::Path>()?;
+                    Ok(Code(
+                        path.segments
+                            .iter()
+                            .map(|s| s.ident.to_string())
+                            .collect::<Vec<_>>()
+                            .join("::"),
+                    ))
+                }
+            } else {
+                input.parse::<Token![=]>()?;
+                Ok(Code(input.parse::<syn::LitStr>()?.value()))
+            }
+        } else {
+            Err(syn::Error::new(ident.span(), "diagnostic code is required. Use #[diagnostic(code = ...)] or #[diagnostic(code(...))] to define one."))
+        }
+    }
+}
+
+impl Code {
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Code,
+            |ident, fields, DiagnosticConcreteArgs { code, .. }| {
+                let code = &code.as_ref()?.0;
+                Some(match fields {
+                    syn::Fields::Named(_) => {
+                        quote! { Self::#ident { .. } => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                    syn::Fields::Unnamed(_) => {
+                        quote! { Self::#ident(..) => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                    syn::Fields::Unit => {
+                        quote! { Self::#ident => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self) -> Option<TokenStream> {
+        let code = &self.0;
+        Some(quote! {
+            fn code(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                std::option::Option::Some(std::boxed::Box::new(#code))
+            }
+        })
+    }
+}