Currently there is:

    Snippet
      PersistentSnippet
        ImportSnippet
        DeclarationSnippet
          MethodDeclSnippet
          VariableDeclSnippet
          TypeDeclSnippet
      StatementSnippet
      ExpressionSnippet
      ErroneousSnippet

and these Kind values corresponding to concrete classes:

    IMPORT
    METHOD_DECL
    VARIABLE_DECL
    TYPE_DECL
    STATEMENT
    EXPRESSION
    ERRONEOUS

I've heard objections to the XxxDeclSnippet format of names. My issue with just dropping it Decl is that "Variable" alone is somewhat ambiguous (to which I've heard the suggestion, of using "Var"), and more significantly that "Type" by itself is just plane confusing.

So, these changes ---

          MethodSnippet
          VarSnippet
          TypeDeclSnippet

and:

    METHOD
    VAR
    TYPE_DECL

And corresponding changes in *Key.