yewstack/yew · error · syn::Error

byte-strings can't be converted to HTML text note: remove th

Error message

byte-strings can't be converted to HTML text
note: remove the `b` prefix or convert this to a `String`

What it means

`HtmlNode::parse` accepts literals as HTML text children, but a byte-string literal (`b"…"`, of type `&[u8; N]`) has no text representation in the virtual DOM, so it is rejected at its span with instructions to drop the `b` prefix or convert to a `String` (html_node.rs:20-27). The check runs before any code generation.

Source

Thrown at packages/yew-macro/src/html_tree/html_node.rs:23

use syn::spanned::Spanned;
use syn::{Expr, Lit};

use super::ToNodeIterator;
use crate::PeekValue;
use crate::stringify::Stringify;

pub enum HtmlNode {
    Literal(Box<Lit>),
    Expression(Box<Expr>),
}

impl Parse for HtmlNode {
    fn parse(input: ParseStream) -> Result<Self> {
        let node = if HtmlNode::peek(input.cursor()).is_some() {
            let lit = input.parse()?;
            match lit {
                Lit::ByteStr(lit) => {
                    return Err(syn::Error::new(
                        lit.span(),
                        "byte-strings can't be converted to HTML text
                         note: remove the `b` prefix or convert this to a `String`",
                    ));
                }
                Lit::Verbatim(lit) => {
                    return Err(syn::Error::new(lit.span(), "unsupported literal"));
                }
                _ => (),
            }
            HtmlNode::Literal(Box::new(lit))
        } else {
            HtmlNode::Expression(Box::new(input.parse()?))
        };

        Ok(node)
    }
}

View on GitHub (pinned to 0e4a05472f)

Solutions

1. Remove the `b` prefix if the content is text: `{ "payload" }`
2. If it is truly binary, decode first: `String::from_utf8_lossy(&BYTES)` and interpolate the result
3. For non-UTF-8 data, render a placeholder (hex dump, byte count) computed in plain Rust

Example fix

// before
html! { <p>{ b"payload" }</p> }

// after
html! { <p>{ "payload" }</p> }

When it happens

Trigger: `html! { <p>{ b"raw bytes" }</p> }` — any byte-string literal used where an HTML child (text) is expected.

Common situations: Interfacing with binary protocols or embedded assets and pasting a `b"…"` sample into markup, or code near `include_bytes!` where a byte literal is mistaken for ordinary text.

Related errors

• unsupported literal
• string literals must not contain more than one class (hint:
• expected a valid closing tag for component note: found openi
• missing condition for `if` expression
• this `if` expression has a condition, but no block

AI-assisted analysis of yewstack/yew@0e4a05472f (2026-08-22). Data as JSON: /api/errors/3589d161babab286. Report an issue: GitHub.