add array ctor refs

modules/lang-painless/src/main/antlr/PainlessParser.g4

@@ -209,7 +209,7 @@ classFuncref
 // reference to a constructor, e.g. ArrayList::new
 // currently limited to simple non-array types
 constructorFuncref
-    : TYPE REF NEW
+    : decltype REF NEW
     ;
 
 // reference to an instance method, e.g. object::toString

modules/lang-painless/src/main/java/org/elasticsearch/painless/antlr/PainlessParser.java

@@ -2969,7 +2969,9 @@ class PainlessParser extends Parser {
   }
 
   public static class ConstructorFuncrefContext extends ParserRuleContext {
-    public TerminalNode TYPE() { return getToken(PainlessParser.TYPE, 0); }
+    public DecltypeContext decltype() {
+      return getRuleContext(DecltypeContext.class,0);
+    }
     public TerminalNode REF() { return getToken(PainlessParser.REF, 0); }
     public TerminalNode NEW() { return getToken(PainlessParser.NEW, 0); }
     public ConstructorFuncrefContext(ParserRuleContext parent, int invokingState) {
@@ -2990,7 +2992,7 @@ class PainlessParser extends Parser {
       enterOuterAlt(_localctx, 1);
       {
       setState(460);
-      match(TYPE);
+      decltype();
       setState(461);
       match(REF);
       setState(462);
@@ -3350,7 +3352,7 @@ class PainlessParser extends Parser {
     "\u01c4\u01c9\5\66\34\2\u01c5\u01c9\58\35\2\u01c6\u01c9\5:\36\2\u01c7\u01c9"+
     "\5<\37\2\u01c8\u01c4\3\2\2\2\u01c8\u01c5\3\2\2\2\u01c8\u01c6\3\2\2\2\u01c8"+
     "\u01c7\3\2\2\2\u01c9\65\3\2\2\2\u01ca\u01cb\7L\2\2\u01cb\u01cc\7\64\2"+
-    "\2\u01cc\u01cd\7M\2\2\u01cd\67\3\2\2\2\u01ce\u01cf\7L\2\2\u01cf\u01d0"+
+    "\2\u01cc\u01cd\7M\2\2\u01cd\67\3\2\2\2\u01ce\u01cf\5\26\f\2\u01cf\u01d0"+
     "\7\64\2\2\u01d0\u01d1\7\26\2\2\u01d19\3\2\2\2\u01d2\u01d3\7M\2\2\u01d3"+
     "\u01d4\7\64\2\2\u01d4\u01d5\7M\2\2\u01d5;\3\2\2\2\u01d6\u01d7\7\32\2\2"+
     "\u01d7\u01d8\7\64\2\2\u01d8\u01d9\7M\2\2\u01d9=\3\2\2\2*AGZ]iq~\u0082"+

modules/lang-painless/src/main/java/org/elasticsearch/painless/antlr/Walker.java

@@ -148,6 +148,7 @@ import org.elasticsearch.painless.node.SWhile;
 
 import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Deque;
 import java.util.List;
 
@@ -166,6 +167,7 @@ public final class Walker extends PainlessParserBaseVisitor<Object> {
     private final String sourceText;
 
     private final Deque<Reserved> reserved = new ArrayDeque<>();
+    private final List<SFunction> synthetic = new ArrayList<>();
 
     private Walker(String sourceName, String sourceText, CompilerSettings settings) {
         this.settings = settings;
@@ -230,6 +232,8 @@ public final class Walker extends PainlessParserBaseVisitor<Object> {
             statements.add((AStatement)visit(statement));
         }
         
+        functions.addAll(synthetic);
+
         return new SSource(sourceName, sourceText, (ExecuteReserved)reserved.pop(), location(ctx), functions, statements);
     }
 
@@ -255,7 +259,7 @@ public final class Walker extends PainlessParserBaseVisitor<Object> {
             statements.add((AStatement)visit(statement));
         }
 
-        return new SFunction((FunctionReserved)reserved.pop(), location(ctx), rtnType, name, paramTypes, paramNames, statements);
+        return new SFunction((FunctionReserved)reserved.pop(), location(ctx), rtnType, name, paramTypes, paramNames, statements, false);
     }
 
     @Override
@@ -974,7 +978,22 @@ public final class Walker extends PainlessParserBaseVisitor<Object> {
 
     @Override
     public Object visitConstructorFuncref(ConstructorFuncrefContext ctx) {
-        return new EFunctionRef(location(ctx), ctx.TYPE().getText(), ctx.NEW().getText());
+        if (!ctx.decltype().LBRACE().isEmpty()) {
+            // array constructors are special: we need to make a synthetic method
+            // taking integer as argument and returning a new instance, and return a ref to that.
+            Location location = location(ctx);
+            String arrayType = ctx.decltype().getText();
+            SReturn code = new SReturn(location, 
+                           new EChain(location,
+                           new LNewArray(location, arrayType, Arrays.asList(
+                           new EChain(location, 
+                           new LVariable(location, "size"))))));
+            String name = "lambda$" + synthetic.size();
+            synthetic.add(new SFunction(new FunctionReserved(), location, arrayType, name, 
+                          Arrays.asList("int"), Arrays.asList("size"), Arrays.asList(code), true));
+            return new EFunctionRef(location(ctx), "this", name);
+        }
+        return new EFunctionRef(location(ctx), ctx.decltype().getText(), ctx.NEW().getText());
     }
 
     @Override

modules/lang-painless/src/main/java/org/elasticsearch/painless/node/EChain.java

@@ -29,6 +29,7 @@ import org.elasticsearch.painless.Operation;
 import org.elasticsearch.painless.Locals;
 import org.elasticsearch.painless.MethodWriter;
 
+import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -47,6 +48,11 @@ public final class EChain extends AExpression {
     Cast there = null;
     Cast back = null;
     
+    /** Creates a new simple EChain */
+    public EChain(Location location, ALink link) {
+        this(location, Arrays.asList(link), false, false, null, null);
+    }
+
     public EChain(Location location, List<ALink> links,
                   boolean pre, boolean post, Operation operation, AExpression expression) {
         super(location);

modules/lang-painless/src/main/java/org/elasticsearch/painless/node/SFunction.java

@@ -50,6 +50,7 @@ public class SFunction extends AStatement {
     final List<String> paramTypeStrs;
     final List<String> paramNameStrs;
     final List<AStatement> statements;
+    final boolean synthetic;
 
     Type rtnType = null;
     List<Parameter> parameters = new ArrayList<>();
@@ -58,7 +59,8 @@ public class SFunction extends AStatement {
     Locals locals = null;
 
     public SFunction(FunctionReserved reserved, Location location,
-                     String rtnType, String name, List<String> paramTypes, List<String> paramNames, List<AStatement> statements) {
+                     String rtnType, String name, List<String> paramTypes, 
+                     List<String> paramNames, List<AStatement> statements, boolean synthetic) {
         super(location);
 
         this.reserved = reserved;
@@ -67,6 +69,7 @@ public class SFunction extends AStatement {
         this.paramTypeStrs = Collections.unmodifiableList(paramTypes);
         this.paramNameStrs = Collections.unmodifiableList(paramNames);
         this.statements = Collections.unmodifiableList(statements);
+        this.synthetic = synthetic;
     }
 
     void generate() {
@@ -138,7 +141,11 @@ public class SFunction extends AStatement {
     
     /** Writes the function to given ClassWriter. */
     void write (ClassWriter writer, BitSet statements) {
-        final MethodWriter function = new MethodWriter(Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC, method.method, writer, statements);
+        int access = Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC;
+        if (synthetic) {
+            access |= Opcodes.ACC_SYNTHETIC;
+        }
+        final MethodWriter function = new MethodWriter(access, method.method, writer, statements);
         write(function);
         function.endMethod();
     }

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

@@ -70,6 +70,10 @@ public class ArrayTests extends ScriptTestCase {
         assertEquals(1, exec("int x; def y = new def[1]; x = y[0] = 1; return x;"));
     }
 
+    public void testArrayVariable() {
+        assertEquals(1, exec("int x = 1; int[] y = new int[x]; return y.length"));
+    }
+
     public void testForLoop() {
         assertEquals(999*1000/2, exec("def a = new int[1000]; for (int x = 0; x < a.length; x++) { a[x] = x; } "+
             "int total = 0; for (int x = 0; x < a.length; x++) { total += a[x]; } return total;"));

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

@@ -57,6 +57,20 @@ public class FunctionRefTests extends ScriptTestCase {
                  "return stats.getSum()"));
     }
 
+    public void testArrayCtorMethodRef() {
+        assertEquals(1.0D, 
+                exec("List l = new ArrayList(); l.add(1.0); l.add(2.0); " + 
+                     "def[] array = l.stream().toArray(Double[]::new);" + 
+                     "return array[0];"));
+    }
+
+    public void testArrayCtorMethodRefDef() {
+        assertEquals(1.0D, 
+                exec("def l = new ArrayList(); l.add(1.0); l.add(2.0); " + 
+                     "def[] array = l.stream().toArray(Double[]::new);" + 
+                     "return array[0];"));
+    }
+
     public void testCapturingMethodReference() {
         assertEquals("5", exec("Integer x = Integer.valueOf(5); return Optional.empty().orElseGet(x::toString);"));
         assertEquals("[]", exec("List l = new ArrayList(); return Optional.empty().orElseGet(l::toString);"));