[foreign-memaccess+abi] RFR: Improve exception messages and simplify LayoutPath [v8]

[Gavin Ray]

On Wed, 20 Sep 2023 16:42:07 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:
> 
>   Rework bredcrumbs appearance

Could I make a suggestion?

For the following `MemoryLayout`:


        MemoryLayout struct = MemoryLayout.structLayout(
                MemoryLayout.sequenceLayout(2, MemoryLayout.structLayout(
                                JAVA_INT.withOrder(ByteOrder.LITTLE_ENDIAN).withName("3a"),
                                JAVA_INT.withOrder(ByteOrder.LITTLE_ENDIAN).withName("3b")
                        ).withName("2")
                ).withName("1")
        ).withName("0");


I find the notation like:

                "[i4(3a)i4(3b)](2), selected from: " +
                "[2:[i4(3a)i4(3b)](2)](1), selected from: " +
                "[[2:[i4(3a)i4(3b)](2)](1)](0)";


Difficult to interpret. Maybe something like the below could be clearer/easier-to-read?

(0: struct)
├── (1: sequence) x 2
│   ├── (2: struct)      ERROR: Invalid sequence selection!
│   │   ├── (3a: i4 LE)
│   │   └── (3b: i4 LE)

-------------

PR Comment: https://git.openjdk.org/panama-foreign/pull/886#issuecomment-1731740775