Add proper signatureHelp for unapply methods #15203
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rochala
commented
May 17, 2022
| patterns: List[tpd.Tree] | ||
| )(using Context): (Int, Int, List[SingleDenotation]) = | ||
| val patternPosition = patterns.indexWhere(_.span.contains(span)) | ||
| val activeParameter = extractParamTypess(fun.tpe.finalResultType.widen).headOption.map { params => |
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Possible performance optimization as this is computed twice. We need to find number of parameters we can unapply to but i can't pass it without changing the API
tgodzik
approved these changes
May 18, 2022
| List(productAccessors.map(_.info.finalResultType).toList) | ||
| else | ||
| ref.symbol.primaryConstructor.paramInfo.paramInfoss | ||
| case AppliedType(TypeRef(_, cls), (appliedType @ AppliedType(tycon, args)) :: Nil) |
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Are you able to add examples to each case to say in which situation each is needed?
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I managed to simplify this logic and added comments why each case is necessary for proper handling
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SignatureHelp is used in LSP to provide help when applying or unapplying.
The real value is displaying each parameter name, type and documentation to make it easier to understand and use given method.
Currently dotty signatureHelp allowed to easily show unapply signatures but with 2 problems:
It was caused by returning signature of unapply method, not its return type.
This implementation makes signatureHelp useful.
Example:
Previously:
After changes:
Provided tests checks all supported syntax for unapply available in Scala3. They were created according to https://docs.scala-lang.org/scala3/reference/changed-features/pattern-matching.html
Returned value contains parameter names only when result is a case class, only then we are certain that unapply patterns match its apply method ( there is also check if unapply is synthetic to check for possible overrides ).
SIgnature help for unapply doesn't show values for tuples as they act as clutter.
There are possible peformance optimizations to be made in places where i left comments in this PR, but I can't find better way to do it without changing existing API.
Fixes #15126