RFR: 8328481: Implement Module Imports [v4]

[Maurizio Cimadamore]

On Tue, 9 Apr 2024 13:38:29 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> This is an implementation of JEP JDK-8315129: Module Import Declarations (Preview). Please see the JEP for details:
>> https://bugs.openjdk.org/browse/JDK-8315129
>> 
>> It is mostly straightforward - the module imports are parsed, and then expanded to import-on-demand in `TypeEnter`.
>> There is a few notable aspects, however:
>> - the AST node for import (`JCImport`) is holding the imported element as a field access, because so far, the imported element always had to have a '.' (even for import-on-demand). But for module imports, it is permissible to import from a module whose name does not have a dot (`import module m;`). The use of field access for ordinary import seems very useful, so I preferred to keep that, and created a new internal-only AST node for module imports. There is still only one public API AST node/interface, so this is purely an implementation choice.
>> - JShell now supports module imports as well; and the default, implicit, script is changed to use it to import all of `java.base` if preview is enabled. It is expected that the default would be changed if/when the module imports feature is finalized.
>
> Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Adding more tests for ambiguities.

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/JCTree.java line 719:

> 717:     public static class JCModuleImport extends JCImportBase {
> 718:         /** The module name. */
> 719:         public JCExpression module;

Does it need to be an expression? Or is a name enough?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18614#discussion_r1559303562