JDK-8262003: Class.arrayType should not throw IllegalArgumentException

[Mandy Chung]

Hi Johannes,

Changing Class::arrayType to throw ISA makes sense to me.   I think 
`TypeDescriptor.ofField::arrayType` spec should also be updated to throw 
ISA to follow what JVM checks for array dimension because it's a static 
constraint check [1] (rather than a resolution error) for `anewarray` 
instruction to create an array no more than 255 dimensions.

The CSR looks okay.  I agree that the compatibility risk is low.

I'd like to review PR along with CSR together.

Mandy
[1] 
https://docs.oracle.com/javase/specs/jvms/se15/html/jvms-4.html#jvms-4.9.1

On 2/23/21 6:38 AM, Johannes Kuhn wrote:
> I want to learn about writing a CSR, and need a sponsor teaching me 
> the ropes.
>
> ----
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8262003
>
> Currently, Class.arrayType() will throw an IllegalArgumentException if 
> the maximum number of dimensions will be exceeded.
>
> Throwing an IllegalArgumentException from a method that doesn't take 
> an argument is, at least, strange.
>
> Therefore I would like to update the specification to allow this 
> method to throw an IllegalStateException, similar to what 
> ClassDesc.arrayType() does.
>
> ----
>
> The current plan is:
>
> * Create a CSR detailing the spec changes: 
> https://bugs.openjdk.java.net/browse/JDK-8262211
> * Surround the code with a try-catch block. Checking for the error 
> case is hard, and somewhat rare, so I think this is appropriate.
> * Copy the @throws javadoc line from ClassDesc.arrayType to 
> Class.arrayType
>
> But there are a few questions I would love to get the answer on:
>
> * Both Class.arrayType() and ClassDesc.arrayType() are specified by 
> TypeDescriptor.OfField. Should the specification of 
> TypeDescriptor.OfField.arrayType() changed as well?
> * Is the draft of my CSR fine? Should I add some details, or omit 
> things? Rephrase things?
>
> In advance, thanks for any support and feedback on this.
>
> - Johannes