xdr_codegen/parser: allow struct members to be declared as 'enum identifier'

Some specs have a construct like

  enum foo {
      A = 0,
      B = 1
  };

  struct blah {
      enum foo type;
      int a;
  };

Previously that wouldn't parse because the member declaration was
expected to start with an identifier, not the keyword 'enum'. But it's a
reasonable construct so there's no reason to disallow it.

Author: bertschinger

xdr_codegen/src/parser.rs

@@ -505,6 +505,12 @@ impl<'src> Parser<'src> {
                 let name = self.expect_identifier("Expected identifier after 'struct'");
                 XdrType::Name(name.to_string())
             }
+            TokenKind::Enum => {
+                // Don't allow anonymous enum declared within outer structs, but do allow using
+                // "enum identifier" as a long form of "identifier":
+                let name = self.expect_identifier("Expected identifier after 'enum'");
+                XdrType::Name(name.to_string())
+            }
             TokenKind::Identifier(name) => XdrType::Name(name.to_string()),
             _ => Parser::error("Expected type specifier to begin declaration", Some(tok)),
         }