Work around Rust hygiene bug.

See: rust-lang/rust#74036

Fixes #14.

assert2-macros/src/hygiene_bug.rs

@@ -0,0 +1,20 @@
+use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
+
+pub fn fix(ts: TokenStream) -> TokenStream {
+	ts.into_iter()
+		.map(|t| match t {
+			TokenTree::Group(g) => {
+				let mut fixed = Group::new(
+					match g.delimiter() {
+						Delimiter::None => Delimiter::Parenthesis,
+						d => d,
+					},
+					fix(g.stream()),
+				);
+				fixed.set_span(g.span());
+				TokenTree::Group(fixed)
+			}
+			t => t,
+		})
+		.collect()
+}

assert2-macros/src/lib.rs

@@ -15,17 +15,19 @@ type FormatArgs = Punctuated<syn::Expr, syn::token::Comma>;
 #[proc_macro_hack]
 #[doc(hidden)]
 pub fn check_impl(tokens: TokenStream) -> TokenStream {
-	check_or_assert_impl(syn::parse_macro_input!(tokens)).into()
+	hygiene_bug::fix(check_or_assert_impl(syn::parse_macro_input!(tokens)).into())
 }
 
+mod hygiene_bug;
+
 #[cfg(feature = "let-assert")]
 mod let_assert;
 
 #[cfg(feature = "let-assert")]
 #[proc_macro]
 #[doc(hidden)]
 pub fn let_assert_impl(tokens: proc_macro::TokenStream) -> proc_macro::TokenStream {
-	let_assert::let_assert_impl(syn::parse_macro_input!(tokens)).into()
+	hygiene_bug::fix(let_assert::let_assert_impl(syn::parse_macro_input!(tokens)).into())
 }
 
 /// Real implementation for assert!() and check!().