Suggest an appropriate token when encountering pub Ident<'a>

Author: estebank

src/libsyntax/parse/parser.rs

@@ -5802,20 +5802,14 @@ impl<'a> Parser<'a> {
     }
 
     fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) {
-        if let Err(mut err) = self.complain_if_pub_macro_diag(vis, sp) {
-            err.emit();
-        }
-    }
-
-    fn complain_if_pub_macro_diag(&mut self, vis: &VisibilityKind, sp: Span) -> PResult<'a, ()> {
         match *vis {
-            VisibilityKind::Inherited => Ok(()),
+            VisibilityKind::Inherited => {}
             _ => {
                 let is_macro_rules: bool = match self.token {
                     token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
                     _ => false,
                 };
-                if is_macro_rules {
+                let mut err = if is_macro_rules {
                     let mut err = self.diagnostic()
                         .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
                     err.span_suggestion_with_applicability(
@@ -5824,13 +5818,14 @@ impl<'a> Parser<'a> {
                         "#[macro_export]".to_owned(),
                         Applicability::MaybeIncorrect // speculative
                     );
-                    Err(err)
+                    err
                 } else {
                     let mut err = self.diagnostic()
                         .struct_span_err(sp, "can't qualify macro invocation with `pub`");
                     err.help("try adjusting the macro to put `pub` inside the invocation");
-                    Err(err)
-                }
+                    err
+                };
+                err.emit();
             }
         }
     }
@@ -7439,6 +7434,28 @@ impl<'a> Parser<'a> {
                     }
                 }
                 return Err(err);
+            } else if self.look_ahead(1, |t| *t == token::Lt) {
+                let ident = self.parse_ident().unwrap();
+                self.eat_to_tokens(&[&token::Gt]);
+                self.bump();
+                let (kw, kw_name, ambiguous) = if self.check(&token::OpenDelim(token::Paren)) {
+                    ("fn", "method", false)
+                } else if self.check(&token::OpenDelim(token::Brace)) {
+                    ("struct", "struct", false)
+                } else {
+                    ("fn` or `struct", "method or struct", true)
+                };
+                let msg = format!("missing `{}` for {} definition", kw, kw_name);
+                let mut err = self.diagnostic().struct_span_err(sp, &msg);
+                if !ambiguous {
+                    err.span_suggestion_short_with_applicability(
+                        sp,
+                        &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
+                        format!(" {} ", kw),
+                        Applicability::MachineApplicable,
+                    );
+                }
+                return Err(err);
             }
         }
         self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)

src/test/ui/pub/pub-ident-fn-with-lifetime.rs

@@ -0,0 +1,6 @@
+pub   foo<'a>(_s: &'a usize) -> bool { true }
+//~^ ERROR missing `fn` for method definition
+
+fn main() {
+    foo(2);
+}

src/test/ui/pub/pub-ident-fn-with-lifetime.stderr

@@ -0,0 +1,12 @@
+error: missing `fn` for method definition
+  --> $DIR/pub-ident-fn-with-lifetime.rs:1:4
+   |
+LL | pub   foo<'a>(_s: &'a usize) -> bool { true }
+   |    ^^^
+help: add `fn` here to parse `foo` as a public method
+   |
+LL | pub fn foo<'a>(_s: &'a usize) -> bool { true }
+   |     ^^
+
+error: aborting due to previous error
+

src/test/ui/pub/pub-ident-struct-with-lifetime.rs

@@ -0,0 +1,4 @@
+pub S<'a> {
+//~^ ERROR missing `struct` for struct definition
+}
+fn main() {}

src/test/ui/pub/pub-ident-struct-with-lifetime.stderr

@@ -0,0 +1,12 @@
+error: missing `struct` for struct definition
+  --> $DIR/pub-ident-struct-with-lifetime.rs:1:4
+   |
+LL | pub S<'a> {
+   |    ^
+help: add `struct` here to parse `S` as a public struct
+   |
+LL | pub struct S<'a> {
+   |     ^^^^^^
+
+error: aborting due to previous error
+

src/test/ui/pub/pub-ident-with-lifetime-incomplete.rs

@@ -0,0 +1,5 @@
+fn main() {
+}
+
+pub   foo<'a>
+//~^ ERROR missing `fn` or `struct` for method or struct definition

src/test/ui/pub/pub-ident-with-lifetime-incomplete.stderr

@@ -0,0 +1,8 @@
+error: missing `fn` or `struct` for method or struct definition
+  --> $DIR/pub-ident-with-lifetime-incomplete.rs:4:4
+   |
+LL | pub   foo<'a>
+   |    ^^^
+
+error: aborting due to previous error
+