cleanup grammar

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

@@ -195,6 +195,30 @@ lamtype
     ;
 
 funcref
-    : TYPE REF ( ID | NEW )
-    | ( ID | THIS ) REF ID
+    : classFuncref
+    | constructorFuncref
+    | capturingFuncref
+    | localFuncref
+    ;
+
+// reference to a static or instance method, e.g. ArrayList::size or Integer::compare
+classFuncref
+    : TYPE REF ID
+	;
+
+// reference to a constructor, e.g. ArrayList::new
+// currently limited to simple non-array types
+constructorFuncref
+    : TYPE REF NEW
+    ;
+
+// reference to an instance method, e.g. object::toString
+// currently limited to capture of a simple variable (id).
+capturingFuncref
+    : ID REF ID
+    ;
+
+// reference to a local function, e.g. this::myfunc
+localFuncref
+    : THIS REF ID
     ;

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

@@ -417,4 +417,32 @@ class PainlessParserBaseVisitor<T> extends AbstractParseTreeVisitor<T> implement
    * {@link #visitChildren} on {@code ctx}.</p>
    */
   @Override public T visitFuncref(PainlessParser.FuncrefContext ctx) { return visitChildren(ctx); }
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The default implementation returns the result of calling
+   * {@link #visitChildren} on {@code ctx}.</p>
+   */
+  @Override public T visitClassFuncref(PainlessParser.ClassFuncrefContext ctx) { return visitChildren(ctx); }
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The default implementation returns the result of calling
+   * {@link #visitChildren} on {@code ctx}.</p>
+   */
+  @Override public T visitConstructorFuncref(PainlessParser.ConstructorFuncrefContext ctx) { return visitChildren(ctx); }
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The default implementation returns the result of calling
+   * {@link #visitChildren} on {@code ctx}.</p>
+   */
+  @Override public T visitCapturingFuncref(PainlessParser.CapturingFuncrefContext ctx) { return visitChildren(ctx); }
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The default implementation returns the result of calling
+   * {@link #visitChildren} on {@code ctx}.</p>
+   */
+  @Override public T visitLocalFuncref(PainlessParser.LocalFuncrefContext ctx) { return visitChildren(ctx); }
 }

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

@@ -397,4 +397,28 @@ interface PainlessParserVisitor<T> extends ParseTreeVisitor<T> {
    * @return the visitor result
    */
   T visitFuncref(PainlessParser.FuncrefContext ctx);
+  /**
+   * Visit a parse tree produced by {@link PainlessParser#classFuncref}.
+   * @param ctx the parse tree
+   * @return the visitor result
+   */
+  T visitClassFuncref(PainlessParser.ClassFuncrefContext ctx);
+  /**
+   * Visit a parse tree produced by {@link PainlessParser#constructorFuncref}.
+   * @param ctx the parse tree
+   * @return the visitor result
+   */
+  T visitConstructorFuncref(PainlessParser.ConstructorFuncrefContext ctx);
+  /**
+   * Visit a parse tree produced by {@link PainlessParser#capturingFuncref}.
+   * @param ctx the parse tree
+   * @return the visitor result
+   */
+  T visitCapturingFuncref(PainlessParser.CapturingFuncrefContext ctx);
+  /**
+   * Visit a parse tree produced by {@link PainlessParser#localFuncref}.
+   * @param ctx the parse tree
+   * @return the visitor result
+   */
+  T visitLocalFuncref(PainlessParser.LocalFuncrefContext ctx);
 }

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

@@ -45,10 +45,13 @@ import org.elasticsearch.painless.antlr.PainlessParser.BraceaccessContext;
 import org.elasticsearch.painless.antlr.PainlessParser.BreakContext;
 import org.elasticsearch.painless.antlr.PainlessParser.CallinvokeContext;
 import org.elasticsearch.painless.antlr.PainlessParser.CalllocalContext;
+import org.elasticsearch.painless.antlr.PainlessParser.CapturingFuncrefContext;
 import org.elasticsearch.painless.antlr.PainlessParser.CastContext;
 import org.elasticsearch.painless.antlr.PainlessParser.ChainprecContext;
+import org.elasticsearch.painless.antlr.PainlessParser.ClassFuncrefContext;
 import org.elasticsearch.painless.antlr.PainlessParser.CompContext;
 import org.elasticsearch.painless.antlr.PainlessParser.ConditionalContext;
+import org.elasticsearch.painless.antlr.PainlessParser.ConstructorFuncrefContext;
 import org.elasticsearch.painless.antlr.PainlessParser.ContinueContext;
 import org.elasticsearch.painless.antlr.PainlessParser.DeclContext;
 import org.elasticsearch.painless.antlr.PainlessParser.DeclarationContext;
@@ -71,6 +74,7 @@ import org.elasticsearch.painless.antlr.PainlessParser.IfContext;
 import org.elasticsearch.painless.antlr.PainlessParser.InitializerContext;
 import org.elasticsearch.painless.antlr.PainlessParser.LambdaContext;
 import org.elasticsearch.painless.antlr.PainlessParser.LamtypeContext;
+import org.elasticsearch.painless.antlr.PainlessParser.LocalFuncrefContext;
 import org.elasticsearch.painless.antlr.PainlessParser.NewarrayContext;
 import org.elasticsearch.painless.antlr.PainlessParser.NewobjectContext;
 import org.elasticsearch.painless.antlr.PainlessParser.NullContext;
@@ -950,20 +954,36 @@ public final class Walker extends PainlessParserBaseVisitor<Object> {
 
     @Override
     public Object visitFuncref(FuncrefContext ctx) {
-        if (ctx.TYPE() != null) {
-            // non-capturing Type::method or Type::new
-            final String methodText;
-            if (ctx.NEW() != null) {
-                methodText = ctx.NEW().getText();
-            } else {
-                methodText = ctx.ID(0).getText();
-            }
-            return new EFunctionRef(location(ctx), ctx.TYPE().getText(), methodText);
-        } else if (ctx.THIS() != null) {
-            return new EFunctionRef(location(ctx), ctx.THIS().getText(), ctx.ID(0).getText());
+        if (ctx.classFuncref() != null) {
+            return visit(ctx.classFuncref());
+        } else if (ctx.constructorFuncref() != null) {
+            return visit(ctx.constructorFuncref());
+        } else if (ctx.capturingFuncref() != null) {
+            return visit(ctx.capturingFuncref());
+        } else if (ctx.localFuncref() != null) {
+            return visit(ctx.localFuncref());
         } else {
-            // capturing object::method
-            return new ECapturingFunctionRef(location(ctx), ctx.ID(0).getText(), ctx.ID(1).getText());
+            throw location(ctx).createError(new IllegalStateException("Illegal tree structure."));
         }
     }
+
+    @Override
+    public Object visitClassFuncref(ClassFuncrefContext ctx) {
+        return new EFunctionRef(location(ctx), ctx.TYPE().getText(), ctx.ID().getText());
+    }
+
+    @Override
+    public Object visitConstructorFuncref(ConstructorFuncrefContext ctx) {
+        return new EFunctionRef(location(ctx), ctx.TYPE().getText(), ctx.NEW().getText());
+    }
+
+    @Override
+    public Object visitCapturingFuncref(CapturingFuncrefContext ctx) {
+        return new ECapturingFunctionRef(location(ctx), ctx.ID(0).getText(), ctx.ID(1).getText());
+    }
+
+    @Override
+    public Object visitLocalFuncref(LocalFuncrefContext ctx) {
+        return new EFunctionRef(location(ctx), ctx.THIS().getText(), ctx.ID().getText());
+    }
 }