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Fix/matches span #400

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merged 2 commits into from Jun 12, 2020
+23 −13
Merged

Fix/matches span #400

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0a6bc51
Use proper span when generating `matches` token
Aaron1011 Jun 12, 2020
83894e2
Some tweaks
CreepySkeleton Jun 12, 2020
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13 changes: 11 additions & 2 deletions structopt-derive/src/lib.rs
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Expand Up @@ -28,7 +28,7 @@ use crate::{

use proc_macro2::{Span, TokenStream};
use proc_macro_error::{abort, abort_call_site, proc_macro_error, set_dummy};
use quote::{quote, quote_spanned};
use quote::{format_ident, quote, quote_spanned};
use syn::{punctuated::Punctuated, spanned::Spanned, token::Comma, *};

/// Default casing style for generated arguments.
Expand Down Expand Up @@ -239,6 +239,16 @@ fn gen_augmentation(
}

fn gen_constructor(fields: &Punctuated<Field, Comma>, parent_attribute: &Attrs) -> TokenStream {
// This ident is used in several match branches below,
// and the `quote[_spanned]` invocations have different spans.
//
// Given that this ident is used in several places and
// that the branches are located inside of a loop, it is possible that
// this ident will be given _different_ spans in different places, and
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Note that a plain quote { } or format_ident will always use Span::call_site() for hygiene, so the generated matches token will always be 'the same' from the perspective of the compiler's name resolution. However, this change is still a good idea, since it makes it clear that matches is logically independent of the loop.

// thus will not be the _same_ ident anymore. To make sure the `matches`
// is always the same, we factor it out.
let matches = format_ident!("matches");

let fields = fields.iter().map(|field| {
let attrs = Attrs::from_field(
field,
Expand All @@ -248,7 +258,6 @@ fn gen_constructor(fields: &Punctuated<Field, Comma>, parent_attribute: &Attrs)
);
let field_name = field.ident.as_ref().unwrap();
let kind = attrs.kind();
let matches = quote! { matches };
match &*kind {
Kind::ExternalSubcommand => abort!(
kind.span(),
Expand Down