RFR: 8340831: Simplify simple validation for class definition in MethodHandles.Lookup

[Claes Redestad]

On Tue, 24 Sep 2024 22:07:25 GMT, Chen Liang <liach at openjdk.org> wrote:

> `MethodHandles.Lookup` defines a `ClassFile` for simple validations; it is unnecessary and can be scalarized manually. The removal of `ClassFile` class is also slightly helpful for bootstrap by reducing class loading. Also improved class file version checking in `VM` class.

Changes requested by redestad (Reviewer).

src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 2276:

> 2274:                 var thisClass = cm.thisClass();
> 2275:                 name = thisClass.asInternalName();
> 2276:                 sym = thisClass.asSymbol();

We only use this for determining package name are equal, and sym.packageName() does the similar transformations plus a bit more. Likely not a significant cost compared to the `ClassFile::parse` - but perhaps there's room for a utility method to get the package name directly from an internal name?

src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 2440:

> 2438:         }
> 2439: 
> 2440:         record ClassDefiner(Lookup lookup, String name, byte[] bytes, int classFlags, ClassFileDumper dumper) {

Rename `name` to `internalName`, dropping the explicit `internalName()` method.

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PR Review: https://git.openjdk.org/jdk/pull/21170#pullrequestreview-2327774125
PR Review Comment: https://git.openjdk.org/jdk/pull/21170#discussion_r1774943742
PR Review Comment: https://git.openjdk.org/jdk/pull/21170#discussion_r1774934606