This error message...
Syntax error, insert "EnumBody" to complete ClassBodyDeclarations
...implies that eclipse detected a syntax error in your code.
Presumanbly, you have tried something in the similar lines:
public enum Foo;
which produces the error as:
Syntax error, insert "EnumBody" to complete ClassBodyDeclarations
Some more details about your usecase, program structure, eclipse version, syntax error recovery and reporting components of the Eclipse JVM would have helped us to analyze the error in a better way. However, this error:

signifies that an unusual syntactic error have misled the compiler's syntax error recovery module algorithm. Possibly, it's a bug within eclipse within the Enumerations module which is handled in a different fashion than the other tokens which causes it to be recovered in a different way and hence shows up the syntax error.