fix(parse): requires clause on one-liner and add error when used on non-template #528
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Add handling of lack of empty line after oneliner. Add parsing error when requires is used on non-template
source/parse.h
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| if (!n->template_parameters) { | ||
| error("'requires' only valid for a template"); | ||
| return {}; | ||
| } |
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It's also valid for templated entities (non-templates within templates).
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Could you provide an example?
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t: <T> type = {
f: () requires std::regular<T> = { }
}
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Also, I think the above won't handle the case of generic parameters that use wildcards instead of an explicit template parameter list? Such as
f: (x) requires std::regular<decltype(x)> = { }
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I do think there's value in diagnosing a requires on a non-templated type for type declarations.
Rationale:
- writing a stray
requireson a function already gives a nice Cpp1 diagnostic (e.g., MSVC sayserror C7599: 't::f': a trailing requires clause is only allowed on a templated function) - writing a stray
requireson a type currently lowers it to a nakedrequiresat global scope before the type which leads to a harder-to-understand Cpp1 diagnostic (e.g., MSVC sayserror C2059: syntax error: 'requires', which is correct and indicates the rough issue, but it's not as specific)
So diagnosing the type case in Cpp2 delivers the primary diagnostic usability improvement, plus I think it's easy to code, I think it just needs adding n->is_type() && in the condition Filip already wrote.
I'll modify the PR to try that out...
Restrict new check to types
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Thanks! |
…on-template (hsutter#528) * Fix parsing error of requires clause Add handling of lack of empty line after oneliner. Add parsing error when requires is used on non-template * Update parse.h Restrict new check to types --------- Co-authored-by: Herb Sutter <[email protected]>
All regression tests pass.
Closes #472