Skip to content

Fix link from Macros: blackbox vs whitebox to SIP-19 #627

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Nov 25, 2016
Merged

Fix link from Macros: blackbox vs whitebox to SIP-19 #627

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion overviews/macros/blackbox-whitebox.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ Blackbox def macros are treated differently from def macros of Scala 2.10. The f

1. When an application of a blackbox macro expands into tree `x`, the expansion is wrapped into a type ascription `(x: T)`, where `T` is the declared return type of the blackbox macro with type arguments and path dependencies applied in consistency with the particular macro application being expanded. This invalidates blackbox macros as an implementation vehicle of [type providers](http://meta.plasm.us/posts/2013/07/11/fake-type-providers-part-2/).
1. When an application of a blackbox macro still has undetermined type parameters after Scala's type inference algorithm has finished working, these type parameters are inferred forcedly, in exactly the same manner as type inference happens for normal methods. This makes it impossible for blackbox macros to influence type inference, prohibiting [fundep materialization](/overviews/macros/implicits.html#fundep_materialization).
1. When an application of a blackbox macro is used as an implicit candidate, no expansion is performed until the macro is selected as the result of the implicit search. This makes it impossible to [dynamically calculate availability of implicit macros](/sips/pending/source-locations.html).
1. When an application of a blackbox macro is used as an implicit candidate, no expansion is performed until the macro is selected as the result of the implicit search. This makes it impossible to [dynamically calculate availability of implicit macros](/sips/rejected/source-locations.html).
1. When an application of a blackbox macro is used as an extractor in a pattern match, it triggers an unconditional compiler error, preventing [customizations of pattern matching](https://github.com/paulp/scala/commit/84a335916556cb0fe939d1c51f27d80d9cf980dc) implemented with macros.

Whitebox def macros work exactly like def macros used to work in Scala 2.10. No restrictions of any kind get applied, so everything that could be done with macros in 2.10 should be possible in 2.11 and 2.12.