A type definition snippet, unsurprisingly, defines one or more Pascal types. Only simple types are supported: classes, objects and records that contain methods are not. If you're not sure, the only types supported are those that can be completely defined in the interface section of a unit.
Each type definition snippet must begin with the type keyword as the first non-space text in the source code. Comments may not preceed it. The type keyword is followed by at least one space or newline and then one or more type definitions.
Here's an example of a valid type definition:
type TMyType = 1..20; TMySecondType = array[TMyType] of Integer;
Type definitions may refer to other type definitions or constants, providing they are defined in Delphi units or elsewhere in the database. The snippet's units and dependencies references should indicate where to find the other types and constants. Type definitions must not reference routines or freeform snippets.