Handle implicits with default parameters. #1073
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/rebuild |
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The first commit in this PR was a merge commit which is confusing, I've fixed that and push-forced |
| acc += arg | ||
| argsOrError(pnames1, ptypes1, acc) | ||
| case ambi: AmbiguousImplicits => | ||
| () => s"ambiguous implicits: ${ambi.explanation} of $where" |
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Why not simply return a String?
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Because we do not want to incur the cost of constructing it when the error does not get reported. Error strings are always lazy.
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OK, intuitively I'd think that the cost of creating a closure would be higher than the cost of constructing a String
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Certainly not if the string is interpolated.
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This doesn't work for implicit parameter lists where only some of the parameters have default values: class A
object Impl {
def foo()(implicit ev: Int, x: A = null): Int = 2
def test: Int = {
implicit val ii: Int = 1
foo()
}
}stack trace: https://gist.github.com/smarter/40c990590e42be4b28f5 |
If an implicit parameter has a default, then that default should be taken in case no implicit argument is found.
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Now also handles mixed lists where some implicits have defaults and others don't. |
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I am going to merge because I have to touch this code again for the classtags issue and I don't want to be slowed down with merging the two fixes afterwards. |
Handle implicits with default parameters.
Fixes #576.
run/pending/Meter now compiles; crashes at runtime.
Review by @smarter.