1 files changed, 23 insertions, 23 deletions
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index e9a55af52e8..5de39c8d14d 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -6,7 +6,7 @@ use crate::ext::base::{ExtCtxt, MacEager, MacResult};
 use crate::parse::token::{self, Token};
 use crate::ptr::P;
 use crate::symbol::kw;
-use crate::tokenstream::{TokenTree};
+use crate::tokenstream::{TokenTree, TokenStream};
 
 use smallvec::smallvec;
 use syntax_pos::Span;
@@ -27,12 +27,11 @@ pub type ErrorMap = BTreeMap<Name, ErrorInfo>;
 
 pub fn expand_diagnostic_used<'cx>(ecx: &'cx mut ExtCtxt<'_>,
                                    span: Span,
-                                   token_tree: &[TokenTree])
+                                   tts: TokenStream)
                                    -> Box<dyn MacResult+'cx> {
-    let code = match token_tree {
-        [
-            TokenTree::Token(Token { kind: token::Ident(code, _), .. })
-        ] => code,
+    assert_eq!(tts.len(), 1);
+    let code = match tts.into_trees().next() {
+        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
         _ => unreachable!()
     };
 
@@ -62,20 +61,21 @@ pub fn expand_diagnostic_used<'cx>(ecx: &'cx mut ExtCtxt<'_>,
 
 pub fn expand_register_diagnostic<'cx>(ecx: &'cx mut ExtCtxt<'_>,
                                        span: Span,
-                                       token_tree: &[TokenTree])
+                                       tts: TokenStream)
                                        -> Box<dyn MacResult+'cx> {
-    let (code, description) = match  token_tree {
-        [
-            TokenTree::Token(Token { kind: token::Ident(code, _), .. })
-        ] => {
-            (*code, None)
-        },
-        [
-            TokenTree::Token(Token { kind: token::Ident(code, _), .. }),
-            TokenTree::Token(Token { kind: token::Comma, .. }),
-            TokenTree::Token(Token { kind: token::Literal(token::Lit { symbol, .. }), ..})
-        ] => {
-            (*code, Some(*symbol))
+    assert!(tts.len() == 1 || tts.len() == 3);
+    let mut cursor = tts.into_trees();
+    let code = match cursor.next() {
+        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
+        _ => unreachable!()
+    };
+    let description = match  (cursor.next(), cursor.next()) {
+        (None, None) => None,
+        (
+            Some(TokenTree::Token(Token { kind: token::Comma, .. })),
+            Some(TokenTree::Token(Token { kind: token::Literal(token::Lit { symbol, .. }), ..}))
+        ) => {
+            Some(symbol)
         },
         _ => unreachable!()
     };
@@ -121,12 +121,12 @@ pub fn expand_register_diagnostic<'cx>(ecx: &'cx mut ExtCtxt<'_>,
 
 pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt<'_>,
                                           span: Span,
-                                          token_tree: &[TokenTree])
+                                          tts: TokenStream)
                                           -> Box<dyn MacResult+'cx> {
-    assert_eq!(token_tree.len(), 3);
-    let ident = match &token_tree[2] {
+    assert_eq!(tts.len(), 3);
+    let ident = match tts.into_trees().nth(2) {
         // DIAGNOSTICS ident.
-        &TokenTree::Token(Token { kind: token::Ident(name, _), span })
+        Some(TokenTree::Token(Token { kind: token::Ident(name, _), span }))
         => Ident::new(name, span),
         _ => unreachable!()
     };