Rollup merge of rust-lang#59116 - estebank:comma-sugg, r=petrochenkov

Be more discerning on when to attempt suggesting a comma in a macro invocation

Fix rust-lang#58796.

Author: Mark-Simulacrum

src/libsyntax/tokenstream.rs

@@ -178,9 +178,11 @@ impl TokenStream {
             while let Some((pos, ts)) = iter.next() {
                 if let Some((_, next)) = iter.peek() {
                     let sp = match (&ts, &next) {
-                        ((TokenTree::Token(_, token::Token::Comma), NonJoint), _) |
-                        (_, (TokenTree::Token(_, token::Token::Comma), NonJoint)) => continue,
-                        ((TokenTree::Token(sp, _), NonJoint), _) => *sp,
+                        (_, (TokenTree::Token(_, token::Token::Comma), _)) => continue,
+                        ((TokenTree::Token(sp, token_left), NonJoint),
+                         (TokenTree::Token(_, token_right), _))
+                        if (token_left.is_ident() || token_left.is_lit()) &&
+                            (token_right.is_ident() || token_right.is_lit()) => *sp,
                         ((TokenTree::Delimited(sp, ..), NonJoint), _) => sp.entire(),
                         _ => continue,
                     };

src/test/ui/macros/missing-comma.rs

@@ -6,6 +6,11 @@ macro_rules! foo {
     ($a:ident, $b:ident, $c:ident, $d:ident, $e:ident) => ();
 }
 
+macro_rules! bar {
+    ($lvl:expr, $($arg:tt)+) => {}
+}
+
+
 fn main() {
     println!("{}" a);
     //~^ ERROR expected token: `,`
@@ -17,4 +22,6 @@ fn main() {
     //~^ ERROR no rules expected the token `d`
     foo!(a, b, c d e);
     //~^ ERROR no rules expected the token `d`
+    bar!(Level::Error, );
+    //~^ ERROR unexpected end of macro invocation
 }

src/test/ui/macros/missing-comma.stderr

@@ -1,11 +1,11 @@
 error: expected token: `,`
-  --> $DIR/missing-comma.rs:10:19
+  --> $DIR/missing-comma.rs:15:19
    |
 LL |     println!("{}" a);
    |                   ^
 
 error: no rules expected the token `b`
-  --> $DIR/missing-comma.rs:12:12
+  --> $DIR/missing-comma.rs:17:12
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -16,7 +16,7 @@ LL |     foo!(a b);
    |           help: missing comma here
 
 error: no rules expected the token `e`
-  --> $DIR/missing-comma.rs:14:21
+  --> $DIR/missing-comma.rs:19:21
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -27,7 +27,7 @@ LL |     foo!(a, b, c, d e);
    |                    help: missing comma here
 
 error: no rules expected the token `d`
-  --> $DIR/missing-comma.rs:16:18
+  --> $DIR/missing-comma.rs:21:18
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -38,13 +38,22 @@ LL |     foo!(a, b, c d, e);
    |                 help: missing comma here
 
 error: no rules expected the token `d`
-  --> $DIR/missing-comma.rs:18:18
+  --> $DIR/missing-comma.rs:23:18
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
 ...
 LL |     foo!(a, b, c d e);
    |                  ^ no rules expected this token in macro call
 
-error: aborting due to 5 previous errors
+error: unexpected end of macro invocation
+  --> $DIR/missing-comma.rs:25:23
+   |
+LL | macro_rules! bar {
+   | ---------------- when calling this macro
+...
+LL |     bar!(Level::Error, );
+   |                       ^ missing tokens in macro arguments
+
+error: aborting due to 6 previous errors