runtime(java): Optionally recognise _module_ import declarations

Define "g:java_syntax_previews" and include number 476 in
its list to enable this recognition:
------------------------------------------------------------
        let g:java_syntax_previews = [476]
------------------------------------------------------------

Reference:
https://openjdk.org/jeps/476

closes: #15709

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/syntax/java.vim b/runtime/syntax/java.vim
index bbef266..800faa4 100644
--- a/runtime/syntax/java.vim
+++ b/runtime/syntax/java.vim
@@ -3,7 +3,7 @@
 " Maintainer:		Aliaksei Budavei <0x000c70 AT gmail DOT com>
 " Former Maintainer:	Claudio Fleiner <claudio@fleiner.com>
 " Repository:		https://github.com/zzzyxwvut/java-vim.git
-" Last Change:		2024 Sep 18
+" Last Change:		2024 Sep 19
 
 " Please check :help java.vim for comments on some of the options available.
 
@@ -92,6 +92,13 @@
 syn keyword javaOperator	new instanceof
 syn match   javaOperator	"\<var\>\%(\s*(\)\@!"
 
+if s:ff.IsRequestedPreviewFeature(476)
+  " Module imports can be used in any source file.
+  syn match   javaExternal	"\<import\s\+module\>" contains=javaModuleImport
+  syn keyword javaModuleImport	contained module
+  hi def link javaModuleImport	Statement
+endif
+
 " Since the yield statement, which could take a parenthesised operand,
 " and _qualified_ yield methods get along within the switch block
 " (JLS-17, §3.8), it seems futile to make a region definition for this
diff --git a/runtime/syntax/testdir/dumps/java_module_info_00.dump b/runtime/syntax/testdir/dumps/java_module_info_00.dump
index a80da89..82ef0b2 100644
--- a/runtime/syntax/testdir/dumps/java_module_info_00.dump
+++ b/runtime/syntax/testdir/dumps/java_module_info_00.dump
@@ -1,6 +1,6 @@
 >/+0#0000e05#ffffff0@1| |T|h|i|s| |m|o|d|u|l|e| |d|e|c|l|a|r|a|t|i|o|n| |b|e|l|o|n|g|s| |t|o| |t|h|e| |s|a|m|p|l|e| |p|r|o|j|e|c|t| |p|u|b|l|i|s|h|e|d| |a|t| +0#0000000&@5
 |/+0#0000e05&@1| |h|t@1|p|s|:|/@1|g|i|t|h|u|b|.|c|o|m|/|z@2|y|x|w|v|u|t|/|m|o|d|u|l|e|-|i|n|f|o|.|g|i|t| |.| +0#0000000&@25
-@75
+|i+0#e000e06&|m|p|o|r|t| |m+0#af5f00255&|o|d|u|l|e| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @50
 |i+0#e000e06&|m|p|o|r|t| +0#0000000&|j|a|v|a|.|u|t|i|l|.|S|e|r|v|i|c|e|L|o|a|d|e|r|;| @43
 @75
 |/+0#0000e05&|*@1| +0#0000000&@71
@@ -12,7 +12,7 @@
 | +0#0000e05&|*| |@+0#e000e06&|p|r|o|v|i|d|e|s| |o+0#00e0e07&|r|g|.|d|e|m|o|.|i|n|t|e|r|n|a|l|.|T|e|s|t|a|b|l|e| +0#0000000&@35
 | +0#0000e05&|*| |@+0#e000e06&|s|e@1| +0#0000e05&|S+0#00e0e07&|e|r|v|i|c|e|L|o|a|d|e|r| +0#0000000&@53
 | +0#0000e05&|*|/| +0#0000000&@71
-|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| @47
+|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| |/+0#0000e05&@1| |J|D|K| |2|3|+| |(|-@1|e|n|a|b|l|e|-|p|r|e|v|i|e|w| |-@1|r|e|l|e|a|s|e| |2|3|)|.| +0#0000000&@3
 |{| @73
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|s+0#00e0003&|t|a|t|i|c| +0#0000000&|j|d|k|.|j|f|r|;| @46
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @51
diff --git a/runtime/syntax/testdir/dumps/java_module_info_01.dump b/runtime/syntax/testdir/dumps/java_module_info_01.dump
index 793cb89..039b16f 100644
--- a/runtime/syntax/testdir/dumps/java_module_info_01.dump
+++ b/runtime/syntax/testdir/dumps/java_module_info_01.dump
@@ -1,5 +1,5 @@
 | +0#0000e05#ffffff0|*|/| +0#0000000&@71
-|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| @47
+|m+0#00e0003&|o|d|u|l|e| +0#0000000&|o|r|g|.|m+0#00e0003&|o|d|u|l|e|.+0#0000000&|i|n|f|o|.|d|e|m|o| |/+0#0000e05&@1| |J|D|K| |2|3|+| |(|-@1|e|n|a|b|l|e|-|p|r|e|v|i|e|w| |-@1|r|e|l|e|a|s|e| |2|3|)|.| +0#0000000&@3
 |{| @73
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|s+0#00e0003&|t|a|t|i|c| +0#0000000&|j|d|k|.|j|f|r|;| @46
 @4|r+0#af5f00255&|e|q|u|i|r|e|s| +0#0000000&|j|a|v|a|.|b|a|s|e|;| @51
diff --git a/runtime/syntax/testdir/input/java_module_info.java b/runtime/syntax/testdir/input/java_module_info.java
index bfbea93..0fe49ef 100644
--- a/runtime/syntax/testdir/input/java_module_info.java
+++ b/runtime/syntax/testdir/input/java_module_info.java
@@ -1,6 +1,6 @@
 // This module declaration belongs to the sample project published at
 // https://github.com/zzzyxwvut/module-info.git .
-
+import module java.base;
 import java.util.ServiceLoader;
 
 /**
@@ -12,7 +12,7 @@
  * @provides org.demo.internal.Testable
  * @see ServiceLoader
  */
-module org.module.info.demo
+module org.module.info.demo	// JDK 23+ (--enable-preview --release 23).
 {
 	requires static jdk.jfr;
 	requires java.base;
diff --git a/runtime/syntax/testdir/input/setup/java_module_info.vim b/runtime/syntax/testdir/input/setup/java_module_info.vim
index 2711c1a..b7b818f 100644
--- a/runtime/syntax/testdir/input/setup/java_module_info.vim
+++ b/runtime/syntax/testdir/input/setup/java_module_info.vim
@@ -28,3 +28,5 @@
     cmd:	'RestoreFilename()',
     once:	true,
 }])
+
+g:java_syntax_previews = [476]