[foreign-memaccess+abi] RFR: Improve exception messages and simplify LayoutPath [v6]

[Jorn Vernee]

On Tue, 19 Sep 2023 11:12:47 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes to improve the exception messages in the internal `LayoutPath` class and also do some code simplifications.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add breadcrumbs to exception messages

Thanks for adding the breadcrumbs, I think they could be useful for debugging.

src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java line 101:

> 99:     private final long[] bounds;
> 100:     @Stable
> 101:     private final MethodHandle[] derefAdapters;

I don't see the point in adding `@Stable`. PathElements are typically created on the fly, not used as constants. Adding the annotations just seems like noise/premature optimization until we see a problematic real-world case. Please remove

src/java.base/share/classes/jdk/internal/foreign/LayoutPath.java line 329:

> 327:                     // Take what is before "Layout"
> 328:                     .substring(0, name.indexOf("Layout"))
> 329:                     .toLowerCase(Locale.ROOT);

I'd much prefer the simplicity of just passing in the name of the type as a `String` parameter.

Also, it seems like this wouldn't work for `AddressLayout` ?: `"attempting to select a address element from a non-address layout ..."`

Maybe a couple of simple `checkSequenceLayout`, `checkGroupLayout` would be better to avoid the existing duplication. I kinda feel like the new solution ends up introducing more complexity than it resolves.

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PR Review: https://git.openjdk.org/panama-foreign/pull/886#pullrequestreview-1635362383
PR Review Comment: https://git.openjdk.org/panama-foreign/pull/886#discussion_r1331456380
PR Review Comment: https://git.openjdk.org/panama-foreign/pull/886#discussion_r1331467764