[foreign-memaccess+abi] RFR: Improve exception messages and simplify LayoutPath [v7]

[Jorn Vernee]

On Wed, 20 Sep 2023 13:26:30 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Use distinct methods for type check
>>  - Revert back to the old reref logic
>>  - Remove Stable annotations
>
> src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java line 333:
> 
>> 331:         if (!layoutClass.isAssignableFrom(layout.getClass())) {
>> 332:             throw badLayoutPath(
>> 333:                     String.format("attempting to select a %s element from a non-%s layout: %s (%s)",
> 
> While it is good to see the breadcrumbs, having them enclosed in parentheses creates confusion as the layouts themselves contain parentheses as shown in the example below.
> 
> Is there a better way (e.g. using `{}`)?
> 
> 
> Bad layout path: attempting to select a sequence element from a non-sequence layout: [i4(3a)i4(3b)](2) ([[2:[i4(3a)i4(3b)](2)](1)](0) -> [2:[i4(3a)i4(3b)](2)](1) -> [i4(3a)i4(3b)](2))

Maybe instead of parenthesis, you could have something like : `path =` in the message? Or maybe something like

Bad layout path: attempting to select a sequence element from a non-sequence layout: [i4(3a)i4(3b)](2), selected from: [2:[i4(3a)i4(3b)](2)](1), selected from: [[2:[i4(3a)i4(3b)](2)](1)](0)

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PR Review Comment: https://git.openjdk.org/panama-foreign/pull/886#discussion_r1331726404