proc_macro: Use ToTokens trait in quote macro

Author: SpriteOvO

library/proc_macro/src/quote.rs

@@ -4,7 +4,9 @@
 //! This quasiquoter uses macros 2.0 hygiene to reliably access
 //! items from `proc_macro`, to build a `proc_macro::TokenStream`.
 
-use crate::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
+use crate::{
+    Delimiter, Group, Ident, Literal, Punct, Spacing, Span, ToTokens, TokenStream, TokenTree,
+};
 
 macro_rules! quote_tt {
     (($($t:tt)*)) => { Group::new(Delimiter::Parenthesis, quote!($($t)*)) };
@@ -50,7 +52,7 @@ macro_rules! quote {
     () => { TokenStream::new() };
     ($($t:tt)*) => {
         [
-            $(TokenStream::from(quote_ts!($t)),)*
+            $(ToTokens::into_token_stream(quote_ts!($t)),)*
         ].iter().cloned().collect::<TokenStream>()
     };
 }
@@ -73,7 +75,7 @@ pub fn quote(stream: TokenStream) -> TokenStream {
                 after_dollar = false;
                 match tree {
                     TokenTree::Ident(_) => {
-                        return Some(quote!(Into::<crate::TokenStream>::into(
+                        return Some(quote!(ToTokens::into_token_stream(
                         Clone::clone(&(@ tree))),));
                     }
                     TokenTree::Punct(ref tt) if tt.as_char() == '$' => {}

tests/ui/macros/auxiliary/issue-100199.rs

@@ -1,8 +1,9 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 
-use proc_macro::{quote, Ident, Span, TokenStream, TokenTree};
+use proc_macro::{Ident, Span, TokenStream, TokenTree, quote};
 
 #[proc_macro_attribute]
 pub fn struct_with_bound(_: TokenStream, _: TokenStream) -> TokenStream {

tests/ui/macros/auxiliary/proc_macro_def.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 

tests/ui/proc-macro/auxiliary/cond_plugin.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 

tests/ui/proc-macro/auxiliary/double.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 use proc_macro::*;

tests/ui/proc-macro/auxiliary/generate-dollar-ident.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 use proc_macro::*;

tests/ui/proc-macro/auxiliary/hygiene_example_codegen.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro as proc_macro_renamed; // This does not break `quote!`
 

tests/ui/proc-macro/auxiliary/mixed-site-span.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 use proc_macro::*;
@@ -13,10 +14,8 @@ pub fn proc_macro_rules(input: TokenStream) -> TokenStream {
         let local_use = id("local_use");
         let mut single_quote = Punct::new('\'', Spacing::Joint);
         single_quote.set_span(Span::mixed_site());
-        let label_use: TokenStream = [
-            TokenTree::from(single_quote),
-            id("label_use"),
-        ].iter().cloned().collect();
+        let label_use: TokenStream =
+            [TokenTree::from(single_quote), id("label_use")].iter().cloned().collect();
         quote!(
             struct $item_def;
             let $local_def = 0;

tests/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs

@@ -1,4 +1,5 @@
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 use proc_macro::{TokenStream, quote};

tests/ui/proc-macro/auxiliary/resolved-located-at.rs

@@ -1,6 +1,7 @@
 #![feature(proc_macro_def_site)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
 
 extern crate proc_macro;
 use proc_macro::*;

tests/ui/proc-macro/quote-interpolation.rs

@@ -0,0 +1,16 @@
+//@ check-pass
+
+#![feature(proc_macro_quote)]
+#![feature(proc_macro_totokens)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::*;
+
+fn main() {
+    let x = Ident::new("foo", Span::call_site());
+    let _ = quote! {
+        let $x = 199;
+    };
+}