cfg_select!: allow optional comma after { /* ... */ }

compiler/rustc_parse/src/parser/cfg_select.rs

@@ -7,14 +7,19 @@ use crate::exp;
 use crate::parser::{AttrWrapper, ForceCollect, Parser, Restrictions, Trailing, UsePreAttrPos};
 
 impl<'a> Parser<'a> {
-    /// Parses a `TokenTree` consisting either of `{ /* ... */ }` (and strip the braces) or an
-    /// expression followed by a comma (and strip the comma).
+    /// Parses a `TokenTree` consisting either of `{ /* ... */ }` optionally followed by a comma
+    /// (and strip the braces and the optional comma) or an expression followed by a comma
+    /// (and strip the comma).
     pub fn parse_delimited_token_tree(&mut self) -> PResult<'a, TokenStream> {
         if self.token == token::OpenBrace {
             // Strip the outer '{' and '}'.
             match self.parse_token_tree() {
-                TokenTree::Token(..) => unreachable!("because of the expect above"),
-                TokenTree::Delimited(.., tts) => return Ok(tts),
+                TokenTree::Token(..) => unreachable!("because the current token is a '{{'"),
+                TokenTree::Delimited(.., tts) => {
+                    // Optionally end with a comma.
+                    let _ = self.eat(exp!(Comma));
+                    return Ok(tts);
+                }
             }
         }
         let expr = self.collect_tokens(None, AttrWrapper::empty(), ForceCollect::Yes, |p, _| {

tests/ui/macros/cfg_select.rs

@@ -34,6 +34,7 @@ fn arm_rhs_expr_3() -> i32 {
         any(true) => 1,
         any(false) => 2,
         any(true) => { 42 }
+        any(true) => { 42 },
         any(false) => -1 as i32,
         any(true) => 2 + 2,
         any(false) => "",
@@ -62,7 +63,7 @@ fn expand_to_statements() -> i32 {
 }
 
 type ExpandToType = cfg_select! {
-    unix => u32,
+    unix => { u32 },
     _ => i32,
 };
 
@@ -113,7 +114,7 @@ impl T for S {
     cfg_select! {
         false => {
             fn a() {}
-        }
+        },
         _ => {
             fn b() {}
         }
@@ -145,7 +146,7 @@ cfg_select! {
 
 cfg_select! {
     unix => {}
-    not(unix) => {}
+    not(unix) => {},
     _ => {}
     //~^ WARN unreachable configuration predicate
 }

tests/ui/macros/cfg_select.stderr

@@ -1,5 +1,5 @@
 error: none of the predicates in this `cfg_select` evaluated to true
-  --> $DIR/cfg_select.rs:161:1
+  --> $DIR/cfg_select.rs:162:1
    |
 LL | / cfg_select! {
 LL | |
@@ -8,55 +8,55 @@ LL | | }
    | |_^
 
 error: none of the predicates in this `cfg_select` evaluated to true
-  --> $DIR/cfg_select.rs:166:1
+  --> $DIR/cfg_select.rs:167:1
    |
 LL | cfg_select! {}
    | ^^^^^^^^^^^^^^
 
 error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `=>`
-  --> $DIR/cfg_select.rs:170:5
+  --> $DIR/cfg_select.rs:171:5
    |
 LL |     => {}
    |     ^^
 
 error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found expression
-  --> $DIR/cfg_select.rs:175:5
+  --> $DIR/cfg_select.rs:176:5
    |
 LL |     () => {}
    |     ^^ expressions are not allowed here
 
 error[E0539]: malformed `cfg_select` macro input
-  --> $DIR/cfg_select.rs:180:5
+  --> $DIR/cfg_select.rs:181:5
    |
 LL |     "str" => {}
    |     ^^^^^ expected a valid identifier here
 
 error[E0539]: malformed `cfg_select` macro input
-  --> $DIR/cfg_select.rs:185:5
+  --> $DIR/cfg_select.rs:186:5
    |
 LL |     a::b => {}
    |     ^^^^ expected a valid identifier here
 
 error[E0537]: invalid predicate `a`
-  --> $DIR/cfg_select.rs:190:5
+  --> $DIR/cfg_select.rs:191:5
    |
 LL |     a() => {}
    |     ^^^
 
 error: expected one of `(`, `::`, `=>`, or `=`, found `+`
-  --> $DIR/cfg_select.rs:195:7
+  --> $DIR/cfg_select.rs:196:7
    |
 LL |     a + 1 => {}
    |       ^ expected one of `(`, `::`, `=>`, or `=`
 
 error: expected one of `(`, `::`, `=>`, or `=`, found `!`
-  --> $DIR/cfg_select.rs:201:8
+  --> $DIR/cfg_select.rs:202:8
    |
 LL |     cfg!() => {}
    |        ^ expected one of `(`, `::`, `=>`, or `=`
 
 warning: unreachable configuration predicate
-  --> $DIR/cfg_select.rs:136:5
+  --> $DIR/cfg_select.rs:137:5
    |
 LL |     _ => {}
    |     - always matches
@@ -70,7 +70,7 @@ LL | #![warn(unreachable_cfg_select_predicates)] // Unused warnings are disabled
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unreachable configuration predicate
-  --> $DIR/cfg_select.rs:142:5
+  --> $DIR/cfg_select.rs:143:5
    |
 LL |     true => {}
    |     ---- always matches
@@ -78,25 +78,25 @@ LL |     _ => {}
    |     ^ this configuration predicate is never reached
 
 warning: unreachable configuration predicate
-  --> $DIR/cfg_select.rs:149:5
+  --> $DIR/cfg_select.rs:150:5
    |
 LL |     _ => {}
    |     ^ this configuration predicate is never reached
 
 warning: unreachable configuration predicate
-  --> $DIR/cfg_select.rs:155:5
+  --> $DIR/cfg_select.rs:156:5
    |
 LL |     test => {}
    |     ^^^^ this configuration predicate is never reached
 
 warning: unreachable configuration predicate
-  --> $DIR/cfg_select.rs:157:5
+  --> $DIR/cfg_select.rs:158:5
    |
 LL |     _ => {}
    |     ^ this configuration predicate is never reached
 
 warning: unexpected `cfg` condition name: `a`
-  --> $DIR/cfg_select.rs:195:5
+  --> $DIR/cfg_select.rs:196:5
    |
 LL |     a + 1 => {}
    |     ^ help: found config with similar value: `target_feature = "a"`
@@ -107,7 +107,7 @@ LL |     a + 1 => {}
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: unexpected `cfg` condition name: `cfg`
-  --> $DIR/cfg_select.rs:201:5
+  --> $DIR/cfg_select.rs:202:5
    |
 LL |     cfg!() => {}
    |     ^^^