allow multiple parameters using an underscore as name #1493
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They're now turned into gensyms, via (the misnamed) `isDiscardUnderscore`, leading to them not being added to the symbol table by `addParamOrResult`. So that gensyms are handled properly, `instantiateBody` now calls `addParams` - which calls `addParamOrResult` - instead of manually adding all parameter symbols to the symbol table via `addDecl`.
Single underscore names in C don't have any special meaning. They're mangled with their parameter position to yield a locally unique name.
If not ignored, they could be selected by named parameter passing, which would mean that they're not really hidden anymore.
zerbina
added
compiler/sem
|
I'm not exactly happy with the implementation yet. Forward declarations and re-definition checks also don't consider anonymous parameters at the moment. An alternative implementation could use |
saem
reviewed
Feb 22, 2025
| @@ -0,0 +1,9 @@ | |||
| discard """ | |||
| description: ''' | |||
| An underscore parameter cannot be reference in named parameter passing. | |||
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Suggested change
| An underscore parameter cannot be reference in named parameter passing. | |
| An underscore parameter cannot be referenced in named parameter passing. |
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Summary
Using an underscore as a parameter's name now makes the symbol
anonymous, allowing multiple parameters to use a single underscore.
This affects all routine definitions as well procedure type.
Details
The motivation is to not require one to give a name to unused
parameters, which is often the case for procedure type parameters and
sometimes for lambda expression parameters. It also makes the meaning
of a single underscore used in a definition context more consistent.
In
semProcTypeNode(which is called for all parameter lists),isDiscardUnderscoreis called on the parameter symbol, marking it asa gensym in case it's an underscore, thus preventing it from later
being added to the symbol table. The manual name check ignores
underscore parameters.
So that underscore parameters cannot be referenced in named parameter
passing,
getNamedParamFromListignores underscore parameters.Notes for Reviewers
definition positions (i.e., creating an anonymous entity)