Generalize quote_spanned to accept DelimSpan as span

src/lib.rs

@@ -619,28 +619,28 @@ macro_rules! quote_spanned {
 #[macro_export]
 macro_rules! quote_spanned {
     ($span:expr=>) => {{
-        let _: $crate::__private::Span = $span;
+        let _ = $crate::__private::IntoSpan::into_span($span);
         $crate::__private::TokenStream::new()
     }};
 
     // Special case rule for a single tt, for performance.
     ($span:expr=> $tt:tt) => {{
         let mut _s = $crate::__private::TokenStream::new();
-        let _span: $crate::__private::Span = $span;
+        let _span = $crate::__private::IntoSpan::into_span($span);
         $crate::quote_token_spanned!{$tt _s _span}
         _s
     }};
 
     // Special case rules for two tts, for performance.
     ($span:expr=> # $var:ident) => {{
         let mut _s = $crate::__private::TokenStream::new();
-        let _: $crate::__private::Span = $span;
+        let _ = $crate::__private::IntoSpan::into_span($span);
         $crate::ToTokens::to_tokens(&$var, &mut _s);
         _s
     }};
     ($span:expr=> $tt1:tt $tt2:tt) => {{
         let mut _s = $crate::__private::TokenStream::new();
-        let _span: $crate::__private::Span = $span;
+        let _span = $crate::__private::IntoSpan::into_span($span);
         $crate::quote_token_spanned!{$tt1 _s _span}
         $crate::quote_token_spanned!{$tt2 _s _span}
         _s
@@ -649,7 +649,7 @@ macro_rules! quote_spanned {
     // Rule for any other number of tokens.
     ($span:expr=> $($tt:tt)*) => {{
         let mut _s = $crate::__private::TokenStream::new();
-        let _span: $crate::__private::Span = $span;
+        let _span = $crate::__private::IntoSpan::into_span($span);
         $crate::quote_each_token_spanned!{_s _span $($tt)*}
         _s
     }};

src/runtime.rs

@@ -2,6 +2,7 @@ use crate::{IdentFragment, ToTokens, TokenStreamExt};
 use core::fmt;
 use core::iter;
 use core::ops::BitOr;
+use proc_macro2::extra::DelimSpan;
 use proc_macro2::{Group, Ident, Punct, Spacing, TokenTree};
 
 pub use core::option::Option;
@@ -165,6 +166,24 @@ impl<T: ToTokens> ToTokens for RepInterp<T> {
     }
 }
 
+pub trait IntoSpan {
+    fn into_span(self) -> Span;
+}
+
+impl IntoSpan for Span {
+    #[inline]
+    fn into_span(self) -> Span {
+        self
+    }
+}
+
+impl IntoSpan for DelimSpan {
+    #[inline]
+    fn into_span(self) -> Span {
+        self.join()
+    }
+}
+
 pub fn push_group(tokens: &mut TokenStream, delimiter: Delimiter, inner: TokenStream) {
     tokens.append(Group::new(delimiter, inner));
 }

tests/ui/wrong-type-span.stderr

@@ -1,8 +1,12 @@
-error[E0308]: mismatched types
+error[E0277]: the trait bound `&str: IntoSpan` is not satisfied
  --> tests/ui/wrong-type-span.rs:6:20
   |
 6 |     quote_spanned!(span=> #x);
   |     ---------------^^^^------
   |     |              |
-  |     |              expected `Span`, found `&str`
-  |     expected due to this
+  |     |              the trait `IntoSpan` is not implemented for `&str`
+  |     required by a bound introduced by this call
+  |
+  = help: the following other types implement trait `IntoSpan`:
+            Span
+            proc_macro2::extra::DelimSpan