| [#980] | project: compiler | priority: low | category: missing feature | |
|---|---|---|---|---|
| submitter | assigned to | status | date submitted | |
| Burak | Martin | won't fix | 2007-03-07 10:26:57.0 | |
| subject | sometimes less inference would be more | |||
| code |
Console.println(List(1,2,3) indexOf { x:Int => x % 2 == 0 })
// what was meant was: findIndexOf |
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| what happened | This compiles and executes, but with a somewhat strange result if one is deceived by the method name:tsf-wpa-2-180:~/Documents/svn/scala buraq$ ./build/quick/bin/scala -nocompdaemon /tmp/gagaga.scala -1 |
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| what expected | Just like with equality ==, the parametric polymorphism seems to defeat the purpose of the type system in some cases. List contains the method
def indexOf[B >: A](elem: B): Int = ...so the type of the anonymous function is simply bumped up to AnyRef :-(:-( It would be nice if the user had more fine-grained control over inference that calls lower bounded methods. The present behavior is very good for method ::, but I claim most uses of lower bounds on type parameters of method are only there to have covariance for some type parameter A of the enclosing class. This would be a use case for an attribute "@don't infer type argument if it is not exactly A" def indexOf. |
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| [back to overview] | ||||
| Martin edited on 2007-03-08 10:44:47.0 |
| I don't really see what we can do here. Unless there's a concrete and implementable proposal how to modify the library and the type system. |