Bootstrap arguments

[John Rose]

On Aug 25, 2011, at 11:23 PM, Jeroen Frijters wrote:

> I was surprised by this as well (from an implementers point of view), because the use of asType is an implementation detail. Normally when you call a method taking a boolean/byte/short/char you also load an int onto the stack, so why would this case be any different?

When you call a function of type, say, (B), you are promising that the 32-bit int you loaded onto the stack fits into the declared subrange, say, -128..127.

(This is a little-known invariant of the verifier.  Although all primitive arguments and return values are passed in 32 and 64 bit containers, some of the 32-bit values are required/guaranteed to be constrained to a subrange of values.)

So if you start with an arbitrary int value (as an ldc produces) you need an extra dynamic operation to force the value into the required subrange.

-- John
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