Add a closure test.

src/wren_compiler.c

@@ -1726,6 +1726,14 @@ static void name(Compiler* compiler, bool allowAssignment)
     return;
   }
 
+  // TODO: The fact that we walk the entire scope chain up to global before
+  // interpreting a name as an implicit "this" call means that surrounding
+  // names shadow ones in the class. This is good for things like globals.
+  // (You wouldn't want `new Fiber` translating to `new this.Fiber`, but may
+  // not be what we want for other names.) One option is to make capitalized
+  // names *always* global, and then a lowercase name will become on an
+  // implicit this if it's not a local in the nearest enclosing class.
+
   // Otherwise, if we are inside a class, it's a call with an implicit "this"
   // receiver.
   ClassCompiler* classCompiler = getEnclosingClass(compiler);

test/closure/reuse_closure_slot.wren

@@ -15,4 +15,3 @@
 }
 
 // TODO: Maximum number of closed-over variables (directly and/or indirect).
-// TODO: Shadow variable used in closure.

test/closure/shadow_closure_with_local.wren

@@ -0,0 +1,11 @@
+{
+  var foo = "closure"
+  new Fn {
+    {
+      IO.print(foo) // expect: closure
+      var foo = "shadow"
+      IO.print(foo) // expect: shadow
+    }
+    IO.print(foo) // expect: closure
+  }.call
+}