Recover from incorrect pub kw in "reasonable" places

Author: estebank

src/libsyntax/parse/parser.rs

@@ -1524,7 +1524,7 @@ impl<'a> Parser<'a> {
                          at_end: &mut bool,
                          mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
         let lo = self.span;
-
+        self.eat_bad_pub();
         let (name, node, generics) = if self.eat_keyword(keywords::Type) {
             self.parse_trait_item_assoc_ty()?
         } else if self.is_const_item() {
@@ -7680,6 +7680,7 @@ impl<'a> Parser<'a> {
 
             let struct_def;
             let mut disr_expr = None;
+            self.eat_bad_pub();
             let ident = self.parse_ident()?;
             if self.check(&token::OpenDelim(token::Brace)) {
                 // Parse a struct variant.
@@ -8618,6 +8619,17 @@ impl<'a> Parser<'a> {
             Applicability::MaybeIncorrect,
         ).emit();
     }
+
+    /// Recover from `pub` keyword in places where it seems _reasonable_ but isn't valid.
+    fn eat_bad_pub(&mut self) {
+        if self.token.is_keyword(keywords::Pub) {
+            self.bump();
+            let mut err = self.diagnostic()
+                .struct_span_err(self.prev_span, "unnecessary visibility qualifier");
+            err.span_label(self.prev_span, "`pub` not permitted here");
+            err.emit();
+        }
+    }
 }
 
 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {

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

@@ -2,9 +2,7 @@
 
 enum Bird {
     pub Duck,
-    //~^ ERROR expected identifier, found keyword `pub`
-    //~| ERROR missing comma
-    //~| WARN variant `pub` should have an upper camel case name
+    //~^ ERROR unnecessary visibility qualifier
     Goose
 }
 

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

@@ -1,26 +1,8 @@
-error: expected identifier, found keyword `pub`
+error: unnecessary visibility qualifier
   --> $DIR/issue-28433.rs:4:5
    |
 LL |     pub Duck,
-   |     ^^^ expected identifier, found keyword
-help: you can escape reserved keywords to use them as identifiers
-   |
-LL |     r#pub Duck,
-   |     ^^^^^
-
-error: missing comma
-  --> $DIR/issue-28433.rs:4:8
-   |
-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
+   |     ^^^ `pub` not permitted here
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 

src/test/ui/parser/trait-pub-assoc-const.rs

@@ -1,6 +1,6 @@
 trait Foo {
     pub const Foo: u32;
-    //~^ ERROR expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found
+    //~^ ERROR unnecessary visibility qualifier
 }
 
 fn main() {}

src/test/ui/parser/trait-pub-assoc-const.stderr

@@ -1,10 +1,8 @@
-error: expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found `pub`
+error: unnecessary visibility qualifier
   --> $DIR/trait-pub-assoc-const.rs:2:5
    |
-LL | trait Foo {
-   |            - expected one of 7 possible tokens here
 LL |     pub const Foo: u32;
-   |     ^^^ unexpected token
+   |     ^^^ `pub` not permitted here
 
 error: aborting due to previous error
 

src/test/ui/parser/trait-pub-assoc-ty.rs

@@ -1,6 +1,6 @@
 trait Foo {
     pub type Foo;
-    //~^ ERROR expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found
+    //~^ ERROR unnecessary visibility qualifier
 }
 
 fn main() {}

src/test/ui/parser/trait-pub-assoc-ty.stderr

@@ -1,10 +1,8 @@
-error: expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found `pub`
+error: unnecessary visibility qualifier
   --> $DIR/trait-pub-assoc-ty.rs:2:5
    |
-LL | trait Foo {
-   |            - expected one of 7 possible tokens here
 LL |     pub type Foo;
-   |     ^^^ unexpected token
+   |     ^^^ `pub` not permitted here
 
 error: aborting due to previous error
 

src/test/ui/parser/trait-pub-method.rs

@@ -1,6 +1,6 @@
 trait Foo {
     pub fn foo();
-    //~^ ERROR expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found
+    //~^ ERROR unnecessary visibility qualifier
 }
 
 fn main() {}

src/test/ui/parser/trait-pub-method.stderr

@@ -1,10 +1,8 @@
-error: expected one of `async`, `const`, `extern`, `fn`, `type`, `unsafe`, or `}`, found `pub`
+error: unnecessary visibility qualifier
   --> $DIR/trait-pub-method.rs:2:5
    |
-LL | trait Foo {
-   |            - expected one of 7 possible tokens here
 LL |     pub fn foo();
-   |     ^^^ unexpected token
+   |     ^^^ `pub` not permitted here
 
 error: aborting due to previous error