Fix pretty-printing of !.

This fixes several FIXMEs in `tests/ui/macros/stringify.rs`.

Author: nnethercote

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -173,12 +173,7 @@ fn space_between(tt1: &TokenTree, tt2: &TokenTree) -> bool {
         // ANYTHING + `,`: `foo,`
         // ANYTHING + `;`: `x = 3;`, `[T; 3]`
         // ANYTHING + `.`: `x.y`, `tup.0`
-        // ANYTHING + `!`: `foo! { ... }`
-        //
-        // FIXME: Incorrect cases:
-        // - Logical not: `x =! y`, `if! x { f(); }`
-        // - Never type: `Fn() ->!`
-        (_, Tok(Token { kind: Comma | Semi | Dot | Not, .. }, _)) => false,
+        (_, Tok(Token { kind: Comma | Semi | Dot, .. }, _)) => false,
 
         // IDENT + `(`: `f(3)`
         //
@@ -189,6 +184,16 @@ fn space_between(tt1: &TokenTree, tt2: &TokenTree) -> bool {
         // `#` + `[`: `#[attr]`
         (Tok(Token { kind: Pound, .. }, _), Del(_, Bracket, _)) => false,
 
+        // `#` + `!`: `#![attr]`
+        (Tok(Token { kind: Pound, .. }, _), Tok(Token { kind: Not, .. }, _)) => false,
+
+        // IDENT + `!`: `println!()`, but `if !x { ... }` needs a space after the `if`
+        (Tok(Token { kind: Ident(sym, is_raw), span }, _), Tok(Token { kind: Not, .. }, _))
+            if !Ident::new(*sym, *span).is_reserved() || *is_raw =>
+        {
+            false
+        }
+
         _ => true,
     }
 }

tests/ui/macros/stringify.rs

@@ -103,13 +103,13 @@ fn test_expr() {
     c1!(expr, [ true || false ], "true || false");
     c1!(expr, [ true || false && false ], "true || false && false");
     c1!(expr, [ a < 1 && 2 < b && c > 3 && 4 > d ], "a < 1 && 2 < b && c > 3 && 4 > d");
-    c2!(expr, [ a & b & !c ], "a & b & !c", "a & b &! c"); // FIXME
+    c2!(expr, [ a & b & !c ], "a & b & !c", "a & b & ! c");
     c2!(expr,
         [ a + b * c - d + -1 * -2 - -3],
         "a + b * c - d + -1 * -2 - -3",
         "a + b * c - d + - 1 * - 2 - - 3"
     );
-    c2!(expr, [ x = !y ], "x = !y", "x =! y"); // FIXME
+    c2!(expr, [ x = !y ], "x = !y", "x = ! y");
 
     // ExprKind::Unary
     c2!(expr, [ *expr ], "*expr", "* expr");
@@ -132,7 +132,7 @@ fn test_expr() {
 
     // ExprKind::If
     c1!(expr, [ if true {} ], "if true {}");
-    c2!(expr, [ if !true {} ], "if !true {}", "if! true {}"); // FIXME
+    c2!(expr, [ if !true {} ], "if !true {}", "if ! true {}");
     c2!(expr,
         [ if ::std::blah() { } else { } ],
         "if ::std::blah() {} else {}",
@@ -725,8 +725,8 @@ fn test_ty() {
     c2!(ty, [ Ref<'a> ], "Ref<'a>", "Ref < 'a >");
     c2!(ty, [ PhantomData<T> ], "PhantomData<T>", "PhantomData < T >");
     c2!(ty, [ PhantomData::<T> ], "PhantomData<T>", "PhantomData :: < T >");
-    c2!(ty, [ Fn() -> ! ], "Fn() -> !", "Fn() ->!");
-    c2!(ty, [ Fn(u8) -> ! ], "Fn(u8) -> !", "Fn(u8) ->!"); // FIXME
+    c1!(ty, [ Fn() -> ! ], "Fn() -> !");
+    c1!(ty, [ Fn(u8) -> ! ], "Fn(u8) -> !");
     c2!(ty, [ <Struct as Trait>::Type ], "<Struct as Trait>::Type", "< Struct as Trait > :: Type");
 
     // TyKind::TraitObject