Fixed defined? for more expressions. Fixes #2611.

lib/compiler/ast/control_flow.rb

@@ -32,6 +32,10 @@ def receiver_sexp
         nil
       end
 
+      def defined(g)
+        g.push_literal "expression"
+      end
+
       def to_sexp
         else_sexp = @else.kind_of?(NilLiteral) ? nil : @else.to_sexp
         sexp = [:case, receiver_sexp]
@@ -328,6 +332,10 @@ def bytecode(g)
         done.set!
       end
 
+      def defined(g)
+        g.push_literal "expression"
+      end
+
       def to_sexp
         else_sexp = @else.kind_of?(NilLiteral) ? nil : @else.to_sexp
         [:if, @condition.to_sexp, @body.to_sexp, else_sexp]
@@ -405,6 +413,10 @@ def bytecode(g, use_gif=true)
         g.pop_modifiers
       end
 
+      def defined(g)
+        g.push_literal "expression"
+      end
+
       def sexp_name
         :while
       end