score:3
Accepted answer
By-name arguments are evaluated whenever they are mentioned. The spec says that right-associative operator method calls are evaluated like this:
a op_: b
desugars to:
{ val someFreshName = a; b.op_:(someFreshName) }
// ↑↑↑
// Eval happens here ↑↑↑
score:10
It's a bug. An old one, at that.
The linked pull request added a compiler warning when using the -Xlint flag:
<console>:13: warning: by-name parameters will be evaluated eagerly when called as a right-associative infix operator. For more details, see SI-1980.
def :: (x: =>Int) = new Node(x) // a right-associative method
^
Source: stackoverflow.com
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