From c1dde60312782619e0e58e4012b93d851a8f2aeb Mon Sep 17 00:00:00 2001
From: Benoit Daloze <benoit.daloze@oracle.com>
Date: Mon, 31 Jul 2023 13:13:25 +0200
Subject: [PATCH] Ensure toArray(TYPE::new) is not used as it's less efficient
 than toArray(TYPE.EMPTY_ARRAY)

---
 src/main/.checkstyle_checks.xml                        | 10 +++++++---
 .../java/org/truffleruby/parser/ast/ArgsParseNode.java |  3 ++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/main/.checkstyle_checks.xml b/src/main/.checkstyle_checks.xml
index a4be9d466c0c..7e3549e28180 100644
--- a/src/main/.checkstyle_checks.xml
+++ b/src/main/.checkstyle_checks.xml
@@ -195,15 +195,19 @@
     </module>
     <module name="RegexpSinglelineJava">
       <property name="format" value='\.toArray\(new \w+\[\w+\.size\(\)\]\)'/>
-      <property name="message" value='Use toArray(new Type[0]) instead.'/>
+      <property name="message" value='Use toArray(Type.EMPTY_ARRAY) instead.'/>
     </module>
     <module name="RegexpSinglelineJava">
       <property name="format" value='new\s+\w+\[\]\s*\{\s*\}'/>
-      <property name="message" value='Use new Type[0] instead.'/>
+      <property name="message" value='Use EMPTY_ARRAY = new Type[0] instead.'/>
     </module>
     <module name="RegexpSinglelineJava">
       <property name="format" value='(?!=)\S\s*new\s+\w+\[0\]'/>
-      <property name="message" value='Use a EMPTY_type_ARRAY constant instead.'/>
+      <property name="message" value='Use a Type.EMPTY_ARRAY or EMPTY_type_ARRAY constant instead.'/>
+    </module>
+    <module name="RegexpSinglelineJava">
+      <property name="format" value='.toArray\(.+\[\]::new\)'/>
+      <property name="message" value='Use .toArray(Type.EMPTY_ARRAY) instead, because this avoids extra allocations.'/>
     </module>
     <module name="RegexpSinglelineJava">
       <property name="format" value="transferToInterpreterOnException"/>
diff --git a/src/main/java/org/truffleruby/parser/ast/ArgsParseNode.java b/src/main/java/org/truffleruby/parser/ast/ArgsParseNode.java
index 81fb62443ce8..ae11809b9d1d 100644
--- a/src/main/java/org/truffleruby/parser/ast/ArgsParseNode.java
+++ b/src/main/java/org/truffleruby/parser/ast/ArgsParseNode.java
@@ -38,6 +38,7 @@
 import java.util.Arrays;
 import java.util.List;
 
+import org.truffleruby.core.string.StringUtils;
 import org.truffleruby.language.SourceIndexLength;
 import org.truffleruby.language.methods.Arity;
 import org.truffleruby.parser.Helpers;
@@ -153,7 +154,7 @@ private Arity createArity() {
             final List<String> keywords = new ArrayList<>(requiredKeywords);
             keywords.addAll(optionalKeywords);
 
-            keywordArguments = keywords.toArray(String[]::new);
+            keywordArguments = keywords.toArray(StringUtils.EMPTY_STRING_ARRAY);
             requiredKeywordArgumentsCount = requiredKeywords.size();
         } else {
             keywordArguments = Arity.NO_KEYWORDS;