Consider making expr_no_struct public

[audunhalland]

Hi, I'm working on a macro where I want to parse the basic structure of a match expression, but then I want to provide my own custom parser for the body of each match arm:

let match_token: syn::Token![match] = input.parse()?;
let expr: syn::Expr = input.parse()?; // <--- issue
let content;
let brace_token = syn::braced!(content in input);

let mut arms = Vec::new();
while !content.is_empty() {
    arms.push(content.call(MyMatchArm::parse)?);
}

match foo { pat => ... } is now incorrectly parsed, because expr: Expr consumes all of foo { pat => ... }. What I need is some way to invoke expr_no_struct, which I think will correctly parse this, but it's not exposed as a public API, and I'd like to avoid copy/pasting hundreds of lines :)

Perhaps a way to do this could be to introduce a public newtype like ExprNoStruct(Expr) and implement Parse for that?

[taiki-e]

Related: #515

[dtolnay]

Closing as a duplicate of #515.