Began Scala-influenced linearization implementation

More information on this implementation and the rationale behind it will
appear in the manual. See future commits.

(Note the TODOs; return values aren't quite right here, but that will be
handled in the next commit.)

lib/MethodWrappers.js

@@ -123,9 +123,6 @@ exports.standard = {
                 : retval;
         };
 
-        // TODO: need a test for this; yes, we want to store a reference
-        ret.___$$proxy_to$$ = proxy_to;
-
         // ensures that proxies can be used to provide concrete
         // implementations of abstract methods with param requirements (we
         // have no idea what we'll be proxying to at runtime, so we need to

lib/Trait.js

@@ -213,23 +213,31 @@ function createVirtProxy( acls, dfn )
             ? 'public'
             : 'protected';
 
+        // this is the aforementioned proxy method; see the docblock for
+        // more information
         dfn[ vis + ' virtual override ' + f ] = ( function()
         {
-            // this is the aforementioned proxy method; see the docblock for
-            // more information
             return function()
             {
                 var pmo = this.___$$pmo$$,
-                    o   = pmo[ f ],
+                    o   = pmo[ f ];
-                    op  = o.___$$proxy_to$$;
 
-                // XXX: a better way to do this would be nice, since this
+                // proxy to virtual override from the class we are mixed
-                // does a substring check on every call; avoids infinite
+                // into, if found; otherwise, proxy to our supertype
-                // recursion from proxying to self
+                return ( o )
-                return ( o && !( op && op.substr( 0, 7 ) === '___$to$' ) )
+                    ? o.apply( pmo, arguments )
-                    ? pmo[ f ].apply( pmo, arguments )
                     : this.__super.apply( this, arguments );
-            }
+            };
+        } )( f );
+
+        // this guy bypasses the above virtual override check, which is
+        // necessary in certain cases to prevent infinte recursion
+        dfn[ vis + ' virtual __$$' + f ] = ( function( f )
+        {
+            return function()
+            {
+                this.___$$parent$$[ f ].apply( this, arguments );
+            };
         } )( f );
     }
 }
@@ -271,7 +279,7 @@ function mixin( trait, dfn, tc )
  * @param  {Object}  src    visibility object to scavenge from
  * @param  {Object}  dest   destination definition object
  * @param  {string}  vis    visibility modifier
- * @param  {string}  ianem  proxy destination (trait instance)
+ * @param  {string}  iname  proxy destination (trait instance)
  *
  * @return  {undefined}
  */
@@ -307,8 +315,9 @@ function mixMethods( src, dest, vis, iname )
         }
         else
         {
-            var virt  = keywords['virtual'] ? 'weak virtual ' : '',
+            var vk = keywords['virtual'],
-                pname = virt + vis + ' proxy ' + f;
+                virt  = vk ? 'weak virtual ' : '',
+                pname = ( vk ? '' : 'proxy ' ) + virt + vis + ' ' + f;
 
             // if we have already set up a proxy for a field of this name,
             // then multiple traits have defined the same concrete member
@@ -318,9 +327,36 @@ function mixMethods( src, dest, vis, iname )
                 throw Error( "Trait member conflict: `" + f + "'" );
             }
 
+            // if non-virtual, a normal proxy should do
+            // TODO: test return value; see below
+            if ( !( keywords['virtual'] ) )
+            {
+                dest[ pname ] = iname;
+                continue;
+            }
+
             // proxy this method to what will be the encapsulated trait
-            // object
+            // object (note that we do not use the proxy keyword here
-            dest[ pname ] = iname;
+            // beacuse we are not proxying to a method of the same name)
+            dest[ pname ] = ( function( f )
+            {
+                return function()
+                {
+                    var pdest = this[ iname ];
+
+                    // invoke the direct method on the trait instance; this
+                    // bypasses the virtual override check on the trait
+                    // method to ensure that it is invoked without
+                    // additional overhead or confusion
+                    var ret = pdest[ '__$$' + f ].apply( pdest, arguments );
+
+                    // TODO: test return value
+                    // if the trait returns itself, return us instead
+                    return ( ret === iname )
+                        ? this
+                        : ret;
+                };
+            } )( f );
         }
     }
 }

test/Trait/LinearizationTest.js

@@ -0,0 +1,80 @@
+/**
+ * Tests trait/class linearization
+ *
+ *  Copyright (C) 2014 Mike Gerwitz
+ *
+ *  This file is part of GNU ease.js.
+ *
+ *  ease.js is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * GNU ease.js adopts Scala's concept of `linearization' with respect to
+ * resolving calls to supertypes; the tests that follow provide a detailed
+ * description of the concept, but readers may find it helpful to read
+ * through the ease.js manual or Scala documentation.
+ */
+
+require( 'common' ).testCase(
+{
+    caseSetUp: function()
+    {
+        this.Sut   = this.require( 'Trait' );
+        this.Class = this.require( 'class' );
+    },
+
+
+    /**
+     * When a class mixes in a trait that defines some method M, and then
+     * overrides it as M', then this.__super within M' should refer to M.
+     * Note that this does not cause any conflicts with any class supertypes
+     * that may define a method of the same name as M, because M must have
+     * been an override, otherwise an error would have occurred.
+     */
+    'Class super call refers to mixin that is part of a class definition':
+    function()
+    {
+        var _self   = this,
+            scalled = false;
+
+        var T = this.Sut(
+        {
+            // after mixin, this should be the super method
+            'virtual public foo': function()
+            {
+                scalled = true;
+            },
+        } );
+
+        this.Class.use( T ).extend(
+        {
+            // overrides mixed-in foo
+            'override public foo': function()
+            {
+                // should invoke T.foo
+                try
+                {
+                    this.__super();
+                }
+                catch ( e )
+                {
+                    _self.fail( false, true,
+                        "Super invocation failure: " + e.message
+                    );
+                }
+            },
+        } )().foo();
+
+        this.assertOk( scalled );
+    },
+} );
+

test/Trait/VirtualTest.js

@@ -17,6 +17,9 @@
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Note that tests for super calls are contained within LinearizationTest;
+ * these test cases simply ensure that overrides are actually taking place.
  */
 
 require( 'common' ).testCase(
@@ -34,23 +37,24 @@ require( 'common' ).testCase(
      */
     'Class inherits virtual trait method': function()
     {
-        var expected = 'foobar';
+        var called = false;
 
         var T = this.Sut(
         {
             'virtual foo': function()
             {
-                return expected;
+                called = true;
             }
         } );
 
         var C = this.Class.use( T ).extend( {} );
 
         // ensure that we are actually using the method
-        this.assertEqual( C().foo(), expected );
+        C().foo();
+        this.assertOk( called, "Virtual method not called" );
 
         // if virtual, we should be able to override it
-        var expected2 = 'foobaz',
+        var called2 = false,
             C2;
 
         this.assertDoesNotThrow( function()
@@ -59,12 +63,13 @@ require( 'common' ).testCase(
             {
                 'override foo': function()
                 {
-                    return expected2;
+                    called2 = true;
                 }
             } );
         } );
 
-        this.assertEqual( C2().foo(), expected2 );
+        C2().foo();
+        this.assertOk( called2, "Method not overridden" );
     },