wip: debug/08-escape-hatch

lab-yue · Feb 4, 2024 · 6e73f7e · 6e73f7e
1 parent 7c1ec9d
commit 6e73f7e
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Showing 3 changed files with 42 additions and 6 deletions.
diff --git a/debug/src/lib.rs b/debug/src/lib.rs
@@ -4,7 +4,7 @@ use proc_macro::TokenStream;
 use quote::{quote, ToTokens};
 use syn::{
     parse_macro_input, AngleBracketedGenericArguments, DeriveInput, ExprLit, GenericArgument, Lit,
-    MetaNameValue, Path, PathArguments, PathSegment, Type, TypePath,
+    Meta, MetaNameValue, Path, PathArguments, PathSegment, Type, TypePath,
 };
 
 #[proc_macro_derive(CustomDebug, attributes(debug))]
@@ -25,6 +25,33 @@ pub fn derive(input: TokenStream) -> TokenStream {
         associated.insert(ty.ident.to_string(), vec![]);
     });
 
+    let custom_bound = input.attrs.iter().find_map(|attr| {
+        if attr.path().is_ident("debug") {
+            if let Ok(meta) = attr.parse_args::<Meta>() {
+                if let Ok(MetaNameValue {
+                    value:
+                        syn::Expr::Lit(ExprLit {
+                            lit: Lit::Str(lit_str),
+                            ..
+                        }),
+                    ..
+                }) = meta.require_name_value()
+                {
+                    return Some(
+                        lit_str
+                            .value()
+                            .parse::<proc_macro2::TokenStream>()
+                            .unwrap_or(
+                                syn::Error::new(lit_str.span(), "expect to be token stream")
+                                    .into_compile_error(),
+                            ),
+                    );
+                }
+            }
+        }
+        None
+    });
+
     let mut fields = vec![];
     match &input.data {
         syn::Data::Struct(s) => {
@@ -58,7 +85,9 @@ pub fn derive(input: TokenStream) -> TokenStream {
                     _ => {}
                 };
 
-                collect_associated_types(&f.ty, &mut associated);
+                if custom_bound.is_none() {
+                    collect_associated_types(&f.ty, &mut associated);
+                }
 
                 let display = match fmt {
                     Some(fmt) => quote!(&format_args!(#fmt, &self.#field_name)),
@@ -98,9 +127,9 @@ pub fn derive(input: TokenStream) -> TokenStream {
 
     let (bound, type_generics) = if bounds.len() > 0 {
         (
-            quote!(
+            custom_bound.unwrap_or(quote!(
                     #(#bounds),*
-            ),
+            )),
             quote!(
                     <#(#types),*>
             ),

diff --git a/debug/tests/progress.rs b/debug/tests/progress.rs
@@ -8,5 +8,5 @@ fn tests() {
     t.pass("tests/05-phantom-data.rs");
     t.pass("tests/06-bound-trouble.rs");
     t.pass("tests/07-associated-type.rs");
-    //t.pass("tests/08-escape-hatch.rs");
+    t.pass("tests/08-escape-hatch.rs");
 }
diff --git a/main.rs b/main.rs
@@ -6,13 +6,20 @@
 // To run the code:
 //     $ cargo run
 use derive_debug::CustomDebug;
+use std::fmt::Debug;
 
 pub trait Trait {
     type Value;
 }
 
 #[derive(CustomDebug)]
-pub struct Field<T: Trait> {
+#[debug(bound = "T::Value: Debug")]
+pub struct Wrapper<T: Trait> {
+    field: Field<T>,
+}
+
+#[derive(CustomDebug)]
+struct Field<T: Trait> {
     values: Vec<T::Value>,
 }