Recover from missing comma between enum variants

Author: estebank

src/libsyntax/parse/parser.rs

@@ -7711,11 +7711,29 @@ impl<'a> Parser<'a> {
             };
             variants.push(respan(vlo.to(self.prev_span), vr));
 
-            if !self.eat(&token::Comma) { break; }
+            if !self.eat(&token::Comma) {
+                if self.token.is_ident() &&
+                    !self.token.is_special_ident() &&
+                    !self.token.is_used_keyword() &&
+                    !self.token.is_unused_keyword()
+                {
+                    let sp = self.sess.source_map().next_point(self.prev_span);
+                    let mut err = self.struct_span_err(sp, "missing comma");
+                    err.span_suggestion_short(
+                        sp,
+                        "missing comma",
+                        ",".to_owned(),
+                        Applicability::MaybeIncorrect,
+                    );
+                    err.emit();
+                } else {
+                    break;
+                }
+            }
         }
         self.expect(&token::CloseDelim(token::Brace))?;
         if !any_disr.is_empty() && !all_nullary {
-            let mut err =self.struct_span_err(
+            let mut err = self.struct_span_err(
                 any_disr.clone(),
                 "discriminator values can only be used with a field-less enum",
             );

src/test/ui/issues/issue-28433.rs

@@ -1,13 +1,14 @@
 // compile-flags: -Z continue-parse-after-error
 
-enum bird {
-    pub duck,
-    //~^ ERROR: expected identifier, found keyword `pub`
-    //~| ERROR: expected
-    goose
+enum Bird {
+    pub Duck,
+    //~^ ERROR expected identifier, found keyword `pub`
+    //~| ERROR missing comma
+    //~| WARN variant `pub` should have an upper camel case name
+    Goose
 }
 
 
 fn main() {
-    let y = bird::goose;
+    let y = Bird::Goose;
 }

src/test/ui/issues/issue-28433.stderr

@@ -1,18 +1,26 @@
 error: expected identifier, found keyword `pub`
   --> $DIR/issue-28433.rs:4:5
    |
-LL |     pub duck,
+LL |     pub Duck,
    |     ^^^ expected identifier, found keyword
 help: you can escape reserved keywords to use them as identifiers
    |
-LL |     r#pub duck,
+LL |     r#pub Duck,
    |     ^^^^^
 
-error: expected one of `(`, `,`, `=`, `{`, or `}`, found `duck`
-  --> $DIR/issue-28433.rs:4:9
+error: missing comma
+  --> $DIR/issue-28433.rs:4:8
    |
-LL |     pub duck,
-   |         ^^^^ expected one of `(`, `,`, `=`, `{`, or `}` here
+LL |     pub Duck,
+   |        ^ help: missing comma
+
+warning: variant `pub` should have an upper camel case name
+  --> $DIR/issue-28433.rs:4:5
+   |
+LL |     pub Duck,
+   |     ^^^ help: convert the identifier to upper camel case: `Pub`
+   |
+   = note: #[warn(non_camel_case_types)] on by default
 
 error: aborting due to 2 previous errors
 

src/test/ui/parser/recover-enum.rs

@@ -3,7 +3,11 @@
 fn main() {
     enum Test {
         Very
-        Bad //~ ERROR found `Bad`
-        Stuff
+        //~^ ERROR missing comma
+        Bad(usize)
+        //~^ ERROR missing comma
+        Stuff { a: usize }
+        //~^ ERROR missing comma
+        Here
     }
 }

src/test/ui/parser/recover-enum.stderr

@@ -1,10 +1,20 @@
-error: expected one of `(`, `,`, `=`, `{`, or `}`, found `Bad`
-  --> $DIR/recover-enum.rs:6:9
+error: missing comma
+  --> $DIR/recover-enum.rs:5:13
    |
 LL |         Very
-   |             - expected one of `(`, `,`, `=`, `{`, or `}` here
-LL |         Bad
-   |         ^^^ unexpected token
+   |             ^ help: missing comma
 
-error: aborting due to previous error
+error: missing comma
+  --> $DIR/recover-enum.rs:7:19
+   |
+LL |         Bad(usize)
+   |                   ^ help: missing comma
+
+error: missing comma
+  --> $DIR/recover-enum.rs:9:27
+   |
+LL |         Stuff { a: usize }
+   |                           ^ help: missing comma
+
+error: aborting due to 3 previous errors