GraphiteEditor/Graphite · error · syn::Error

Failed to parse implementations for argument '{name}': {e}

Error message

Failed to parse implementations for argument '{name}': {e}

What it means

parse_implementations parses an #[implementations(...)] attribute on a plain (non-node) field as a comma-terminated list of bare Rust types (Punctuated<Type, Comma>). When the tokens are not bare types, the syn error is wrapped with the offending argument's identifier so you can find the right parameter.

Source

Thrown at node-graph/node-macro/src/parsing.rs:737

						}
						// Skip Modify* traits as they don't affect usage tracking
						// Also ignore other traits like Ctx, ExtractAll, etc.
						_ => {}
					}
				}
			}
		}
	}

	features
}

fn parse_implementations(attr: &Attribute, name: &Ident) -> syn::Result<Punctuated<Type, Comma>> {
	let content: TokenStream2 = attr.parse_args()?;
	let parser = Punctuated::<Type, Comma>::parse_terminated;
	parser.parse2(content.clone()).map_err(|e| {
		let span = e.span(); // Get the span of the error
		Error::new(span, format!("Failed to parse implementations for argument '{name}': {e}"))
	})
}

fn parse_node_implementations<T: Parse>(attr: &Attribute, name: &Ident) -> syn::Result<Punctuated<T, Comma>> {
	let content: TokenStream2 = attr.parse_args()?;
	let parser = Punctuated::<T, Comma>::parse_terminated;
	parser.parse2(content.clone()).map_err(|e| {
		Error::new(
			e.span(),
			formatdoc!(
				"Invalid #[implementations(...)] for argument `{}`.
				Expected a comma-separated list of `InputType -> OutputType` pairs.
				Example: #[implementations(i32 -> f64, String -> Vec<u8>)]
				Error: {}",
				name,
				e
			),
		)

View on GitHub (pinned to c507b35645)

Solutions

1. Use bare, comma-separated types here: #[implementations(f32, f64)]
2. If node-style pairs were intended, that attribute belongs on a node function's parameter parsed by parse_node_implementations instead
3. Use the argument name in the message to locate which parameter's attribute is malformed

Example fix

// before: pairs on a plain (non-node) field
#[implementations(f64 -> f64)]

// after: bare types
#[implementations(f32, f64)]

When it happens

Trigger: Using node-style pairs where bare types are expected: #[implementations(f64 -> f64)] on a regular field; passing literals or strings; stray tokens left after the last type in the list.

Common situations: Copy-pasting an #[implementations(...)] attribute from a node function parameter onto a plain helper struct field (or vice versa); confusion between the two implementations grammars supported by this codebase.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Failed to parse input type for #[implementation(...)]. Expec
• Expected `->` arrow after input type in #[implementations(..
• Failed to parse output type for #[implementation(...)]. Expe
• Failed to parse node_fn attributes: {e}
• Invalid #[implementations(...)] for argument `{}`. Expected

AI-assisted analysis of GraphiteEditor/Graphite@c507b35645 (2026-08-16). Data as JSON: /api/errors/c6a34a2f60b55ce0. Report an issue: GitHub.