Script: Mangle user function names

modules/lang-painless/src/main/java/org/elasticsearch/painless/FunctionRef.java

@@ -99,7 +99,7 @@ public static FunctionRef create(PainlessLookup painlessLookup, FunctionTable fu
                 isDelegateInterface = false;
                 isDelegateAugmented = false;
                 delegateInvokeType = H_INVOKESTATIC;
-                delegateMethodName = localFunction.getFunctionName();
+                delegateMethodName = localFunction.getMangledName();
                 delegateMethodType = localFunction.getMethodType();
                 delegateInjections = new Object[0];
 

modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultSemanticHeaderPhase.java

@@ -69,6 +69,7 @@ public void visitFunction(SFunction userFunctionNode, ScriptScope scriptScope) {
             typeParameters.add(paramType);
         }
 
-        functionTable.addFunction(functionName, returnType, typeParameters, userFunctionNode.isInternal(), userFunctionNode.isStatic());
+        functionTable.addMangledFunction(functionName, returnType, typeParameters, userFunctionNode.isInternal(),
+                userFunctionNode.isStatic());
     }
 }

modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultUserTreeToIRTreePhase.java

@@ -608,7 +608,11 @@ public void visitFunction(SFunction userFunctionNode, ScriptScope scriptScope) {
 
         FunctionNode irFunctionNode = new FunctionNode(userFunctionNode.getLocation());
         irFunctionNode.setBlockNode(irBlockNode);
-        irFunctionNode.attachDecoration(new IRDName(userFunctionNode.getFunctionName()));
+        String mangledName = scriptScope.getFunctionTable().getFunction(
+                        userFunctionNode.getFunctionName(),
+                        userFunctionNode.getCanonicalTypeNameParameters().size()
+                ).getMangledName();
+        irFunctionNode.attachDecoration(new IRDName(mangledName));
         irFunctionNode.attachDecoration(new IRDReturnType(returnType));
         irFunctionNode.attachDecoration(new IRDTypeParameters(new ArrayList<>(localFunction.getTypeParameters())));
         irFunctionNode.attachDecoration(new IRDParameterNames(new ArrayList<>(userFunctionNode.getParameterNames())));

modules/lang-painless/src/main/java/org/elasticsearch/painless/symbol/FunctionTable.java

@@ -25,9 +25,12 @@
  */
 public class FunctionTable {
 
+    private static final String MANGLED_FUNCTION_NAME_PREFIX = "&";
+
     public static class LocalFunction {
 
         protected final String functionName;
+        protected final String mangledName;
         protected final Class<?> returnType;
         protected final List<Class<?>> typeParameters;
         protected final boolean isInternal;
@@ -38,8 +41,14 @@ public static class LocalFunction {
 
         public LocalFunction(
                 String functionName, Class<?> returnType, List<Class<?>> typeParameters, boolean isInternal, boolean isStatic) {
+            this(functionName, "", returnType, typeParameters, isInternal, isStatic);
+        }
+
+        private LocalFunction(String functionName, String mangle,
+                Class<?> returnType, List<Class<?>> typeParameters, boolean isInternal, boolean isStatic) {
 
             this.functionName = Objects.requireNonNull(functionName);
+            this.mangledName = Objects.requireNonNull(mangle) + this.functionName;
             this.returnType = Objects.requireNonNull(returnType);
             this.typeParameters = Collections.unmodifiableList(Objects.requireNonNull(typeParameters));
             this.isInternal = isInternal;
@@ -49,12 +58,12 @@ public LocalFunction(
             Class<?>[] javaTypeParameters = typeParameters.stream().map(PainlessLookupUtility::typeToJavaType).toArray(Class<?>[]::new);
 
             this.methodType = MethodType.methodType(javaReturnType, javaTypeParameters);
-            this.asmMethod = new org.objectweb.asm.commons.Method(functionName,
+            this.asmMethod = new org.objectweb.asm.commons.Method(mangledName,
                     MethodType.methodType(javaReturnType, javaTypeParameters).toMethodDescriptorString());
         }
 
-        public String getFunctionName() {
-            return functionName;
+        public String getMangledName() {
+            return mangledName;
         }
 
         public Class<?> getReturnType() {
@@ -103,8 +112,11 @@ public LocalFunction addFunction(
         return function;
     }
 
-    public LocalFunction addFunction(LocalFunction function) {
-        String functionKey = buildLocalFunctionKey(function.getFunctionName(), function.getTypeParameters().size());
+    public LocalFunction addMangledFunction(String functionName,
+            Class<?> returnType, List<Class<?>> typeParameters, boolean isInternal, boolean isStatic) {
+        String functionKey = buildLocalFunctionKey(functionName, typeParameters.size());
+        LocalFunction function =
+                new LocalFunction(functionName, MANGLED_FUNCTION_NAME_PREFIX, returnType, typeParameters, isInternal, isStatic);
         localFunctions.put(functionKey, function);
         return function;
     }

modules/lang-painless/src/main/java/org/elasticsearch/painless/toxcontent/DecorationToXContent.java

@@ -466,7 +466,7 @@ public static void ToXContent(PainlessMethod method, XContentBuilderWrapper buil
 
     public static void ToXContent(FunctionTable.LocalFunction localFunction, XContentBuilderWrapper builder) {
         builder.startObject();
-        builder.field("functionName", localFunction.getFunctionName());
+        builder.field("mangledName", localFunction.getMangledName());
         builder.field("returnType", localFunction.getReturnType().getSimpleName());
         if (localFunction.getTypeParameters().isEmpty() == false) {
             builder.field("typeParameters", classNames(localFunction.getTypeParameters()));

modules/lang-painless/src/test/java/org/elasticsearch/painless/UserFunctionTests.java

@@ -8,9 +8,30 @@
 
 package org.elasticsearch.painless;
 
+import java.util.List;
+
 public class UserFunctionTests extends ScriptTestCase {
     public void testZeroArgumentUserFunction() {
         String source = "def twofive() { return 25; } twofive()";
         assertEquals(25, exec(source));
     }
+
+    public void testUserFunctionDefCallRef() {
+        String source =
+            "String getSource() { 'source'; }\n" +
+            "int myCompare(int a, int b) { getMulti() * Integer.compare(a, b) }\n" +
+                "int getMulti() { return -1 }\n" +
+                "def l = [1, 100, -100];\n" +
+                "if (myCompare(10, 50) > 0) { l.add(50 + getMulti()) }\n" +
+                "l.sort(this::myCompare);\n" +
+                "if (l[0] == 100) { l.remove(l.size() - 1) ; l.sort((a, b) -> -1 * myCompare(a, b)) } \n"+
+                "if (getSource().startsWith('sour')) { l.add(255); }\n" +
+                "return l;";
+        assertEquals(List.of(1, 49, 100, 255), exec(source));
+        assertBytecodeExists(source, "public static &getSource()Ljava/lang/String");
+        assertBytecodeExists(source, "public static &getMulti()I");
+        assertBytecodeExists(source, "INVOKESTATIC org/elasticsearch/painless/PainlessScript$Script.&getMulti ()I");
+        assertBytecodeExists(source, "public static &myCompare(II)I");
+        assertBytecodeExists(source, "INVOKESTATIC org/elasticsearch/painless/PainlessScript$Script.&myCompare (II)I");
+    }
 }