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| author | metagn <10591326+metagn@users.noreply.github.com> | 2022-01-20 22:57:50 +0300 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2022-01-20 20:57:50 +0100 |
| commit | 2bd1aa186e09565b2103394bd281478fa1b10ef1 (patch) | |
| tree | 3c1d9b68565f1c2f98fb3691fc4da1a81045460f /doc/manual.rst | |
| parent | 1563cb2f6e37f07c303d095dabde74955be1e523 (diff) | |
| download | Nim-2bd1aa186e09565b2103394bd281478fa1b10ef1.tar.gz | |
New/better macro pragmas, mark some as experimental (#19406)
* New/better macro pragmas, make some experimental fix #15920, close #18212, close #14781, close #6696, close https://github.com/nim-lang/RFCs/issues/220 Variable macro pragmas have been changed to only take a unary section node. They can now also be applied in sections with multiple variables, as well as `const` sections. They also accept arguments. Templates now support macro pragmas, mirroring other routine types. Type and variable macro pragmas have been made experimental. Symbols without parentheses instatiating nullary macros or templates has also been documented in the experimental manual. A check for a redefinition error based on the left hand side of variable definitions when using variable macro pragmas was disabled. This nerfs `byaddr` specifically, however this has been documented as a consequence of the experimental features `byaddr` uses. Given how simple these changes are I'm worried if I'm missing something. * accomodate compiler boot * allow weird pragmas * add test for #10994 * remove some control flow, try remove some logic
Diffstat (limited to 'doc/manual.rst')
| -rw-r--r-- | doc/manual.rst | 28 |
1 files changed, 12 insertions, 16 deletions
diff --git a/doc/manual.rst b/doc/manual.rst index 4eabd0225..2469a0525 100644 --- a/doc/manual.rst +++ b/doc/manual.rst @@ -7781,9 +7781,10 @@ More examples with custom pragmas: Macro pragmas ------------- -All macros and templates can also be used as pragmas. They can be attached -to routines (procs, iterators, etc), type names, or type expressions. The -compiler will perform the following simple syntactic transformations: +Macros and templates can sometimes be called with the pragma syntax. Cases +where this is possible include when attached to routine (procs, iterators, etc) +declarations or routine type expressions. The compiler will perform the +following simple syntactic transformations: .. code-block:: nim template command(name: string, def: untyped) = discard @@ -7810,20 +7811,15 @@ This is translated to: ------ -.. code-block:: nim - type - MyObject {.schema: "schema.protobuf".} = object - -This is translated to a call to the `schema` macro with a `nnkTypeDef` -AST node capturing both the left-hand side and right-hand side of the -definition. The macro can return a potentially modified `nnkTypeDef` tree -or multiple `nnkTypeDef` trees contained in a `nnkTypeSection` node -which will replace the original row in the type section. - -When multiple macro pragmas are applied to the same definition, the -compiler will apply them consequently from left to right. Each macro -will receive as input the output of the previous one. +When multiple macro pragmas are applied to the same definition, the first one +from left to right will be evaluated. This macro can then choose to keep +the remaining macro pragmas in its output, and those will be evaluated in +the same way. +There are a few more applications of macro pragmas, such as in type, +variable and constant declarations, but this behavior is considered to be +experimental and is documented in the `experimental manual +<manual_experimental.html#extended-macro-pragmas>` instead. Foreign function interface |