Only eat semicolons for statements that need them

When parsing a statement (e.g. inside a function body),
we now consider `struct Foo {};` and `$stmt;` to each consist
of two statements: `struct Foo {}` and `;`, and `$stmt` and `;`.

As a result, an attribute macro invoke as
`fn foo() { #[attr] struct Bar{}; }` will see `struct Bar{}` as its
input. Additionally, the 'unused semicolon' lint now fires in more
places.

compiler/rustc_parse/src/parser/stmt.rs

@@ -473,8 +473,7 @@ pub fn parse_full_stmt(
                 // so capture it
                 add_semi_token(local.tokens.as_mut());
             }
-            StmtKind::Empty => eat_semi = false,
-            _ => {}
+            StmtKind::Empty | StmtKind::Item(_) | StmtKind::Semi(_) => eat_semi = false,
         }
 
         if eat_semi && self.eat(&token::Semi) {

src/test/ui/proc-macro/allowed-attr-stmt-expr.stdout

@@ -261,7 +261,7 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         span: $DIR/allowed-attr-stmt-expr.rs:53:54: 53:56 (#0),
     },
 ]
-PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other { } ;
+PRINT-ATTR INPUT (DISPLAY): #[rustc_dummy] struct Other { }
 PRINT-ATTR INPUT (DEBUG): TokenStream [
     Punct {
         ch: '#',
@@ -291,9 +291,4 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
         stream: TokenStream [],
         span: $DIR/allowed-attr-stmt-expr.rs:57:18: 57:20 (#0),
     },
-    Punct {
-        ch: ';',
-        spacing: Alone,
-        span: $DIR/allowed-attr-stmt-expr.rs:57:20: 57:21 (#0),
-    },
 ]