8357178: Simplify Class::componentType

[liach]

isArray and null return is now redundant when componentType is changed to an explicit field.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8357178: Simplify Class::componentType (Enhancement - P5)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25280/head:pull/25280
$ git checkout pull/25280

Update a local copy of the PR:
$ git checkout pull/25280
$ git pull https://git.openjdk.org/jdk.git pull/25280/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25280

View PR using the GUI difftool:
$ git pr show -t 25280

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25280.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back liach! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@liach The following label will be automatically applied to this pull request:

• core-libs

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 01: Full - Incremental (f8f0bf65)
• 00: Full (272ee25d)

[jddarcy]

Did you consider calling getComponentType(), which already returns the field?

Are there regression tests for Class::componentType()/Class::getComponentType() somewhere? I didn't see them in the obvious test/jdk/java/lang/Class directory.

[liach]

Did you consider calling getComponentType(), which already returns the field?

I don't think we want an extra indirection here - The logic here is quite simple. Counterargument could be that MethodType::descriptorString calls toMethodDescriptorString, except these methods involve more complex caching and is not simple like this field access.

Are there regression tests for Class::componentType()/Class::getComponentType() somewhere? I didn't see them in the obvious test/jdk/java/lang/Class directory.

They are located in test/jdk/java/lang/constant/TypeDescriptorTest.java.

[jddarcy]

Did you consider calling getComponentType(), which already returns the field?

I don't think we want an extra indirection here - The logic here is quite simple. Counterargument could be that MethodType::descriptorString calls toMethodDescriptorString, except these methods involve more complex caching and is not simple like this field access.

My mental model anyway is that this trivial inline would be something the VM would do readily.

[minborg]

Question: Why was this overload added in the first place, as it seems equivalent to getComponentType()?

[liach]

@minborg It implements a method in TypeDescriptor.OfField.