Update to syn 2

.clippy.toml

@@ -1 +1 @@
-msrv = "1.31.0"
+msrv = "1.56.0"

.github/workflows/ci.yml

@@ -40,19 +40,6 @@ jobs:
         if: matrix.rust == 'nightly'
       - run: cargo test --all
 
-  msrv:
-    name: Rust 1.31.0
-    needs: pre_ci
-    if: needs.pre_ci.outputs.continue
-    runs-on: ubuntu-latest
-    timeout-minutes: 45
-    steps:
-      - uses: actions/checkout@v3
-      - uses: dtolnay/rust-toolchain@1.31.0
-        with:
-          components: rust-src
-      - run: cargo check
-
   clippy:
     name: Clippy
     runs-on: ubuntu-latest

Cargo.toml

@@ -9,7 +9,7 @@ edition = "2018"
 keywords = ["error", "error-handling", "derive"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/thiserror"
-rust-version = "1.31"
+rust-version = "1.56"
 
 [dependencies]
 thiserror-impl = { version = "=1.0.39", path = "impl" }

README.md

@@ -16,7 +16,7 @@ This library provides a convenient derive macro for the standard library's
 thiserror = "1.0"
 ```
 
-*Compiler support: requires rustc 1.31+*
+*Compiler support: requires rustc 1.56+*
 
 <br>
 

impl/Cargo.toml

@@ -6,15 +6,15 @@ description = "Implementation detail of the `thiserror` crate"
 edition = "2018"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/dtolnay/thiserror"
-rust-version = "1.31"
+rust-version = "1.56"
 
 [lib]
 proc-macro = true
 
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = "1.0.45"
+syn = "2.0"
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]

impl/src/attr.rs

@@ -2,9 +2,9 @@ use proc_macro2::{Delimiter, Group, Span, TokenStream, TokenTree};
 use quote::{format_ident, quote, ToTokens};
 use std::collections::BTreeSet as Set;
 use std::iter::FromIterator;
-use syn::parse::{Nothing, ParseStream};
+use syn::parse::ParseStream;
 use syn::{
-    braced, bracketed, parenthesized, token, Attribute, Error, Ident, Index, LitInt, LitStr,
+    braced, bracketed, parenthesized, token, Attribute, Error, Ident, Index, LitInt, LitStr, Meta,
     Result, Token,
 };
 
@@ -54,24 +54,27 @@ pub fn get(input: &[Attribute]) -> Result<Attrs> {
     };
 
     for attr in input {
-        if attr.path.is_ident("error") {
+        if attr.path().is_ident("error") {
             parse_error_attribute(&mut attrs, attr)?;
-        } else if attr.path.is_ident("source") {
+        } else if attr.path().is_ident("source") {
             require_empty_attribute(attr)?;
             if attrs.source.is_some() {
                 return Err(Error::new_spanned(attr, "duplicate #[source] attribute"));
             }
             attrs.source = Some(attr);
-        } else if attr.path.is_ident("backtrace") {
+        } else if attr.path().is_ident("backtrace") {
             require_empty_attribute(attr)?;
             if attrs.backtrace.is_some() {
                 return Err(Error::new_spanned(attr, "duplicate #[backtrace] attribute"));
             }
             attrs.backtrace = Some(attr);
-        } else if attr.path.is_ident("from") {
-            if !attr.tokens.is_empty() {
-                // Assume this is meant for derive_more crate or something.
-                continue;
+        } else if attr.path().is_ident("from") {
+            match attr.meta {
+                Meta::Path(_) => {}
+                Meta::List(_) | Meta::NameValue(_) => {
+                    // Assume this is meant for derive_more crate or something.
+                    continue;
+                }
             }
             if attrs.from.is_some() {
                 return Err(Error::new_spanned(attr, "duplicate #[from] attribute"));
@@ -166,21 +169,21 @@ fn parse_token_expr(input: ParseStream, mut begin_expr: bool) -> Result<TokenStr
             let delimiter = parenthesized!(content in input);
             let nested = parse_token_expr(&content, true)?;
             let mut group = Group::new(Delimiter::Parenthesis, nested);
-            group.set_span(delimiter.span);
+            group.set_span(delimiter.span.join());
             TokenTree::Group(group)
         } else if input.peek(token::Brace) {
             let content;
             let delimiter = braced!(content in input);
             let nested = parse_token_expr(&content, true)?;
             let mut group = Group::new(Delimiter::Brace, nested);
-            group.set_span(delimiter.span);
+            group.set_span(delimiter.span.join());
             TokenTree::Group(group)
         } else if input.peek(token::Bracket) {
             let content;
             let delimiter = bracketed!(content in input);
             let nested = parse_token_expr(&content, true)?;
             let mut group = Group::new(Delimiter::Bracket, nested);
-            group.set_span(delimiter.span);
+            group.set_span(delimiter.span.join());
             TokenTree::Group(group)
         } else {
             input.parse()?
@@ -191,8 +194,15 @@ fn parse_token_expr(input: ParseStream, mut begin_expr: bool) -> Result<TokenStr
 }
 
 fn require_empty_attribute(attr: &Attribute) -> Result<()> {
-    syn::parse2::<Nothing>(attr.tokens.clone())?;
-    Ok(())
+    let error_span = match &attr.meta {
+        Meta::Path(_) => return Ok(()),
+        Meta::List(meta) => meta.delimiter.span().open(),
+        Meta::NameValue(meta) => meta.eq_token.span,
+    };
+    Err(Error::new(
+        error_span,
+        "unexpected token in thiserror attribute",
+    ))
 }
 
 impl ToTokens for Display<'_> {

impl/src/expand.rs

@@ -528,8 +528,7 @@ fn type_parameter_of_option(ty: &Type) -> Option<&Type> {
 
 fn spanned_error_trait(input: &DeriveInput) -> TokenStream {
     let vis_span = match &input.vis {
-        Visibility::Public(vis) => Some(vis.pub_token.span),
-        Visibility::Crate(vis) => Some(vis.crate_token.span),
+        Visibility::Public(vis) => Some(vis.span),
         Visibility::Restricted(vis) => Some(vis.pub_token.span),
         Visibility::Inherited => None,
     };