pprust: Do not print spaces before some tokens

src/libsyntax/print/pprust.rs

@@ -152,6 +152,18 @@ pub fn to_string<F>(f: F) -> String where
     printer.s.eof()
 }
 
+// This makes comma-separated lists look slightly nicer,
+// and also addresses a specific regression described in issue #63896.
+fn tt_prepend_space(tt: &TokenTree) -> bool {
+    match tt {
+        TokenTree::Token(token) => match token.kind {
+            token::Comma => false,
+            _ => true,
+        }
+        _ => true,
+    }
+}
+
 fn binop_to_string(op: BinOpToken) -> &'static str {
     match op {
         token::Plus     => "+",
@@ -696,7 +708,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target=pp::Printer> + std::ops::DerefM
 
     fn print_tts(&mut self, tts: tokenstream::TokenStream, convert_dollar_crate: bool) {
         for (i, tt) in tts.into_trees().enumerate() {
-            if i != 0 {
+            if i != 0 && tt_prepend_space(&tt) {
                 self.space();
             }
             self.print_tt(tt, convert_dollar_crate);

src/test/pretty/attr-literals.rs

@@ -5,10 +5,10 @@
 #![feature(rustc_attrs)]
 
 fn main() {
-    #![rustc_dummy("hi" , 1 , 2 , 1.012 , pi = 3.14 , bye , name ("John"))]
+    #![rustc_dummy("hi", 1, 2, 1.012, pi = 3.14, bye, name ("John"))]
     #[rustc_dummy = 8]
     fn f() { }
 
-    #[rustc_dummy(1 , 2 , 3)]
+    #[rustc_dummy(1, 2, 3)]
     fn g() { }
 }

src/test/pretty/block-comment-wchar.pp

@@ -99,8 +99,5 @@ fn main() {
          '\u{2004}', '\u{2005}', '\u{2006}', '\u{2007}', '\u{2008}',
          '\u{2009}', '\u{200A}', '\u{2028}', '\u{2029}', '\u{202F}',
          '\u{205F}', '\u{3000}'];
-    for c in &chars {
-        let ws = c.is_whitespace();
-        println!("{} {}" , c , ws);
-    }
+    for c in &chars { let ws = c.is_whitespace(); println!("{} {}", c, ws); }
 }

src/test/pretty/delimited-token-groups.rs

@@ -5,7 +5,7 @@
 macro_rules! mac { ($ ($ tt : tt) *) => () }
 
 mac! {
-    struct S { field1 : u8 , field2 : u16 , } impl Clone for S
+    struct S { field1 : u8, field2 : u16, } impl Clone for S
     {
         fn clone () -> S
         {

src/test/pretty/do1.rs

@@ -2,4 +2,4 @@
 
 fn f<F>(f: F) where F: Fn(isize) { f(10) }
 
-fn main() { f(|i| { assert_eq!(i , 10) }) }
+fn main() { f(|i| { assert_eq!(i, 10) }) }

src/test/pretty/match-block-expr.rs

@@ -2,5 +2,5 @@
 
 fn main() {
     let x = match { 5 } { 1 => 5, 2 => 6, _ => 7, };
-    assert_eq!(x , 7);
+    assert_eq!(x, 7);
 }

src/test/ui/macros/macro-first-set.rs

@@ -25,7 +25,7 @@ macro_rules! foo_26444 {
 }
 
 fn test_26444() {
-    assert_eq!("a , b , c , d , e", foo_26444!(a, b; c; d, e));
+    assert_eq!("a, b, c, d, e", foo_26444!(a, b; c; d, e));
     assert_eq!("f", foo_26444!(; f ;));
 }
 

src/test/ui/proc-macro/auxiliary/attr-stmt-expr-rpass.rs

@@ -17,7 +17,7 @@ pub fn expect_let(attr: TokenStream, item: TokenStream) -> TokenStream {
 #[proc_macro_attribute]
 pub fn expect_print_stmt(attr: TokenStream, item: TokenStream) -> TokenStream {
     assert!(attr.to_string().is_empty());
-    assert_eq!(item.to_string(), "println!(\"{}\" , string);");
+    assert_eq!(item.to_string(), "println!(\"{}\", string);");
     item
 }
 
@@ -31,7 +31,7 @@ pub fn expect_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
 #[proc_macro_attribute]
 pub fn expect_print_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
     assert!(attr.to_string().is_empty());
-    assert_eq!(item.to_string(), "println!(\"{}\" , string)");
+    assert_eq!(item.to_string(), "println!(\"{}\", string)");
     item
 }
 

src/test/ui/proc-macro/auxiliary/attr-stmt-expr.rs

@@ -17,7 +17,7 @@ pub fn expect_let(attr: TokenStream, item: TokenStream) -> TokenStream {
 #[proc_macro_attribute]
 pub fn expect_print_stmt(attr: TokenStream, item: TokenStream) -> TokenStream {
     assert!(attr.to_string().is_empty());
-    assert_eq!(item.to_string(), "println!(\"{}\" , string);");
+    assert_eq!(item.to_string(), "println!(\"{}\", string);");
     item
 }
 
@@ -31,7 +31,7 @@ pub fn expect_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
 #[proc_macro_attribute]
 pub fn expect_print_expr(attr: TokenStream, item: TokenStream) -> TokenStream {
     assert!(attr.to_string().is_empty());
-    assert_eq!(item.to_string(), "println!(\"{}\" , string)");
+    assert_eq!(item.to_string(), "println!(\"{}\", string)");
     item
 }