Scala interpreter has a problem with else in new line

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Open scala interpreter and load a file that contains

val half =
	if (n % 2 == 0) 
		n / 2 
	else 
		throw new RuntimeException("n must be even")

--> illegal start of definition

whereas

val half = if (n % 2 == 0) n / 2 else throw new RuntimeException("n must be even") 

works fine.

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Imported From: https://issues.scala-lang.org/browse/SI-1945?orig=1
Reporter: Thomas (foofighter)

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@paulp said (edited by @som-snytt on Aug 31, 2013 5:40:52 PM UTC):
Sorry, this is a limitation of the interpreter. val half = if (x) y is a valid statement all by itself, so when you press enter it is processed. Avoiding this would require forcing everyone to press enter twice all the time, which is no good.

You can do this:

val half = (
    if (n % 2 == 0)
        n / 2
    else
        throw new RuntimeException("n must be even")
)

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@som-snytt said:
One heuristic is that if line 2 fails with a syntax error, try again with line 1 + line 2.

This works exactly if line 1 is a prefix of the combined input that compiles.

You could capture more errors by retrying with typer errors, for example, postfix expressions that are currently handled by the leading-dot syntax:

> List("one"->2)
> toMap

but I'm guessing there are edge cases.

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@som-snytt said:
Here is that PR: scala/scala#2989

Not reopening until consensus.