# What variables (like @type) are available in macros? **URL:** \ **Category:** Help & Support\ **Created:** [December 21, 2023, 10:50am UTC](https://forum.crystal-lang.org/t/what-variables-like-type-are-available-in-macros/6233 "2023-12-21T10:50:55Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Jochen](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/jochen/32/3490_2.png) [@Jochen](https://forum.crystal-lang.org/u/Jochen)\ **Post date:** [December 21, 2023, 10:50am UTC](https://forum.crystal-lang.org/t/what-variables-like-type-are-available-in-macros/6233/1 "2023-12-21T10:50:55Z")
Hi, I read about @type in macros in the docs, and found @def in the code, but are there any other variables available? I’m preparing a pull request to update the docs, if there are any others that should be added it would be nice to know about them. ---
**Author:** ![straight-shoota](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/straight-shoota/32/36_2.png) [@straight-shoota](https://forum.crystal-lang.org/u/straight-shoota)\ **Post date:** [December 21, 2023, 11:18am UTC](https://forum.crystal-lang.org/t/what-variables-like-type-are-available-in-macros/6233/2 "2023-12-21T11:18:43Z")
That’s great, thanks for picking this up 🫶 There’s also `@top_level` which refers to the `Program` i.e. the top level scope. All macro meta vars are defined in a single place in the macro interpreter: > There’s an additional var, `@caller` coming in ([Expose macro `Call` context via new `@caller` macro ivar by Blacksmoke16 · Pull Request #14048 · crystal-lang/crystal · GitHub](https://github.com/crystal-lang/crystal/pull/14048)) and it already has a docs PR: [Document new `@caller` macro ivar by Blacksmoke16 · Pull Request #724 · crystal-lang/crystal-book · GitHub](https://github.com/crystal-lang/crystal-book/pull/724) You might want to start working on top of that (not required, but could be easier in order to incorporate everything). ---
**Author:** ![straight-shoota](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/straight-shoota/32/36_2.png) [@straight-shoota](https://forum.crystal-lang.org/u/straight-shoota)\ **Post date:** [December 21, 2023, 11:20am UTC](https://forum.crystal-lang.org/t/what-variables-like-type-are-available-in-macros/6233/3 "2023-12-21T11:20:52Z")
And please note that the semantics of `@type` are a bit… _wanky_. This may need refinement. > > > The \[documentation for \`@type\`\](https://crystal-lang.org/reference/1.10/syntax\_a…nd\_semantics/macros/index.html#type-information) reads: > \> When a macro is invoked you can access the current scope, or type, with a special instance variable: \`@type\`. \[...\] > \> Note that \`@type\` is always the \*instance\* type, even when the macro is invoked in a class method. > > This is a bit unspecific about what "current scope" actually means. It could be the scope where the macro is defined or the caller scope. > The note about the instance type seems to point towards the latter, though because it doesn't seem to make sense for the macro scope. > The attached example also shows "current scope" as the caller's scope. However, this was added at a later point (in https://github.com/crystal-lang/crystal-book/pull/153) and just documents the actual behaviour, not necessarily the original intention. > > This is quite different from \`@type\` in a \[macro method\](https://crystal-lang.org/reference/1.10/syntax\_and\_semantics/macros/macro\_methods.html) (a \`def\` with \`{% @type %}\`) which refers to the def's scope. > > Either way, the actual behaviour is quite surprising. The caller scope semantics seems to apply only in macros defined in the top-level scope. Otherwise \`@type\` actually refers to the macro's scope! > > In the following example, the caller's scope would be \`\\` and \`C\`, respectively. But \`@type\` in \`M.foo\` is always \`M\`. > > \`\`\`cr > module M > macro foo > {% p @type %} > end > end > > macro bar > {% p @type %} > end > > bar # =\> \ > M.foo # =\> M > > class C > bar # =\> C > M.foo # =\> M > end > \`\`\` > > This seems pretty wrong. The semantics of \`@type\` should not depend on whether the macro is defined in the top-level scope or not. > > However, it's not immediately clear which semantics are actually intended / "correct". The documentation seems to indicate the caller's scope, but that contradics with \`@type\` in macro methods. It's quite disturbing for the same feature to swap semantics depending on context. > > A related discussion is the introduction of the \`@caller\` meta var (#14048). It references a macro's caller. A reference to the caller's scope could be well integrated for example as \`@caller\_scope\`, \`@caller.@scope\` or the like (IMO \`scope\` fits better than \`type\` and clearly distinguishes from \`@type\`. > > So I think I would tend to prefer \`@type\` to mean the macro's scope as the ideal semantics, exactly like in macro methods. > > But it's not trivial to resolve this to a congruent state either way because it may break existing code depending on one semantic or the other. ---
**Author:** ![Jochen](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/jochen/32/3490_2.png) [@Jochen](https://forum.crystal-lang.org/u/Jochen)\ **Post date:** [December 23, 2023, 1:02am UTC](https://forum.crystal-lang.org/t/what-variables-like-type-are-available-in-macros/6233/4 "2023-12-23T01:02:30Z")
Well, it seems to magically have resolved itself 🙂