Remove unmaintained proc-macro-error2 dependency (RUSTSEC-2026-0173) (#707)

* Remove unmaintained proc-macro-error2 dependency (RUSTSEC-2026-0173)

* Use syn::Error compile error instead of unreachable! for span_pos failure

Author: thomasqueirozb

mlua_derive/Cargo.toml

@@ -13,11 +13,10 @@ license = "MIT"
 proc-macro = true
 
 [features]
-macros = ["proc-macro-error2", "itertools"]
+macros = ["itertools"]
 
 [dependencies]
 quote = "1.0"
 proc-macro2 = { version = "1.0", features = ["span-locations"] }
-proc-macro-error2 = { version = "2.0.1", optional = true }
 syn = { version = "2.0", features = ["full"] }
 itertools = { version = "0.14", optional = true }

mlua_derive/src/chunk/mod.rs

@@ -63,8 +63,8 @@ pub(crate) struct Chunk {
 }
 
 impl Chunk {
-    pub(crate) fn new(tokens: TokenStream) -> Self {
-        let tokens = Tokens::retokenize(tokens);
+    pub(crate) fn new(tokens: TokenStream) -> Result<Self, TokenStream2> {
+        let tokens = Tokens::retokenize(tokens)?;
 
         let mut source = String::new();
         let mut caps = Captures::new();
@@ -91,10 +91,10 @@ impl Chunk {
             prev_end = Some(t.end());
         }
 
-        Self {
+        Ok(Self {
             source: source.trim_end().to_string(),
             caps,
-        }
+        })
     }
 
     pub(crate) fn captures(&self) -> &[Capture] {

mlua_derive/src/chunk/token.rs

@@ -1,10 +1,11 @@
 use std::cmp::{Eq, PartialEq};
+use std::convert::TryFrom;
 use std::fmt::{self, Display, Formatter};
 use std::vec::IntoIter;
 
-use itertools::Itertools;
 use proc_macro::{Delimiter, Span, TokenStream, TokenTree};
-use proc_macro2::Span as Span2;
+use proc_macro2::{Span as Span2, TokenStream as TokenStream2};
+use syn;
 
 #[derive(Clone, Copy, Debug)]
 pub(crate) struct Pos {
@@ -32,19 +33,21 @@ impl Pos {
     }
 }
 
-fn span_pos(span: &Span) -> (Pos, Pos) {
+fn span_pos(span: &Span) -> Result<(Pos, Pos), TokenStream2> {
     let span2: Span2 = (*span).into();
     let start = span2.start();
     let end = span2.end();
 
     // Rust 1.88 stabilized Span APIs, so this branch must be unreachable
     if start.line == 0 || end.line == 0 {
-        proc_macro_error2::abort_call_site!(
-            "cannot retrieve span location information; mlua requires nightly Rust or stable >= 1.88"
-        );
+        return Err(syn::Error::new(
+            Span2::call_site(),
+            "cannot retrieve span location information; mlua requires nightly Rust or stable >= 1.88",
+        )
+        .to_compile_error());
     }
 
-    (Pos::new(start.line, start.column), Pos::new(end.line, end.column))
+    Ok((Pos::new(start.line, start.column), Pos::new(end.line, end.column)))
 }
 
 /// Attribute of token.
@@ -74,33 +77,32 @@ impl PartialEq for Token {
 impl Eq for Token {}
 
 impl Token {
-    fn new(tree: TokenTree) -> Self {
-        let (start, end) = span_pos(&tree.span());
+    fn new(tree: TokenTree) -> Result<Self, TokenStream2> {
+        let (start, end) = span_pos(&tree.span())?;
         let source = tree.span().source_text().unwrap_or_else(|| tree.to_string());
-        Self {
+        Ok(Self {
             source,
             start,
             end,
             tree,
             attr: TokenAttr::None,
-        }
+        })
     }
 
-    fn new_delim(source: String, tree: TokenTree, open: bool) -> Self {
-        let (start, end) = span_pos(&tree.span());
+    fn new_delim(source: String, tree: TokenTree, open: bool) -> Result<Self, TokenStream2> {
+        let (start, end) = span_pos(&tree.span())?;
         let (start, end) = if open {
             (start, start.right())
         } else {
             (end.left(), end)
         };
-
-        Self {
+        Ok(Self {
             source,
             tree,
             start,
             end,
             attr: TokenAttr::None,
-        }
+        })
     }
 
     pub(crate) fn tree(&self) -> &TokenTree {
@@ -133,27 +135,33 @@ impl Token {
 pub(crate) struct Tokens(pub(crate) Vec<Token>);
 
 impl Tokens {
-    pub(crate) fn retokenize(tt: TokenStream) -> Tokens {
-        Tokens(
-            tt.into_iter()
-                .flat_map(Tokens::from)
-                .batching(|iter| {
-                    // Find variable tokens: `$` + `ident` => `$ident`
-                    let t = iter.next()?;
-                    if t.is("$") {
-                        if let Some(next) = iter.next()
-                            && matches!(next.tree, TokenTree::Ident(_))
-                        {
-                            Some(next.attr(TokenAttr::Cap))
-                        } else {
-                            proc_macro_error2::abort!(t.tree.span(), "`$` must be followed by an identifier");
-                        }
-                    } else {
-                        Some(t)
-                    }
-                })
-                .collect(),
-        )
+    pub(crate) fn retokenize(tt: TokenStream) -> Result<Tokens, TokenStream2> {
+        let mut flat = Vec::new();
+        for tree in tt.into_iter() {
+            flat.extend(Tokens::try_from(tree)?.0);
+        }
+
+        let mut tokens = Vec::new();
+        let mut iter = flat.into_iter();
+        while let Some(t) = iter.next() {
+            // Find variable tokens: `$` + `ident` => `$ident`
+            if t.is("$") {
+                if let Some(next) = iter.next()
+                    && matches!(next.tree, TokenTree::Ident(_))
+                {
+                    tokens.push(next.attr(TokenAttr::Cap));
+                } else {
+                    return Err(syn::Error::new(
+                        t.tree.span().into(),
+                        "`$` must be followed by an identifier",
+                    )
+                    .to_compile_error());
+                }
+            } else {
+                tokens.push(t);
+            }
+        }
+        Ok(Tokens(tokens))
     }
 }
 
@@ -166,8 +174,10 @@ impl IntoIterator for Tokens {
     }
 }
 
-impl From<TokenTree> for Tokens {
-    fn from(tt: TokenTree) -> Self {
+impl TryFrom<TokenTree> for Tokens {
+    type Error = TokenStream2;
+
+    fn try_from(tt: TokenTree) -> Result<Self, TokenStream2> {
         let tts = match tt.clone() {
             TokenTree::Group(g) => {
                 let (b, e) = match g.delimiter() {
@@ -178,15 +188,16 @@ impl From<TokenTree> for Tokens {
                 };
                 let (b, e) = (b.into(), e.into());
 
-                vec![Token::new_delim(b, tt.clone(), true)]
-                    .into_iter()
-                    .chain(g.stream().into_iter().flat_map(Tokens::from))
-                    .chain(vec![Token::new_delim(e, tt, false)])
-                    .collect()
+                let mut result = vec![Token::new_delim(b, tt.clone(), true)?];
+                for inner in g.stream().into_iter() {
+                    result.extend(Tokens::try_from(inner)?.0);
+                }
+                result.push(Token::new_delim(e, tt, false)?);
+                result
             }
-            _ => vec![Token::new(tt)],
+            _ => vec![Token::new(tt)?],
         };
-        Tokens(tts)
+        Ok(Tokens(tts))
     }
 }
 

mlua_derive/src/lib.rs

@@ -3,7 +3,7 @@ use proc_macro::TokenStream;
 mod module;
 
 #[cfg(feature = "macros")]
-use {crate::chunk::Chunk, proc_macro_error2::proc_macro_error};
+use crate::chunk::Chunk;
 
 #[cfg(feature = "macros")]
 macro_rules! try_compile {
@@ -22,9 +22,11 @@ pub fn lua_module(attr: TokenStream, item: TokenStream) -> TokenStream {
 
 #[cfg(feature = "macros")]
 #[proc_macro]
-#[proc_macro_error]
 pub fn chunk(input: TokenStream) -> TokenStream {
-    Chunk::new(input).expand().into()
+    match Chunk::new(input) {
+        Ok(chunk) => chunk.expand().into(),
+        Err(err) => err.into(),
+    }
 }
 
 #[cfg(feature = "macros")]