generated function with less dependencies

This commit removes the dependency of generated function to IdSet
because it is not yet defined during the bootstrap stages. By doing
this, we can avoid the world age issues and use @generated function
in abstractarray.jl.

Author: johnnychen94

base/expr.jl

@@ -1684,15 +1684,23 @@ function generated_body_to_codeinfo(ex::Expr, defmod::Module, isva::Bool)
     end
     ci.isva = isva
     code = ci.code
-    bindings = IdSet{Core.Binding}()
+    bindings = Core.svec()
     for i = 1:length(code)
         stmt = code[i]
         if isa(stmt, GlobalRef)
-            push!(bindings, convert(Core.Binding, stmt))
+            # plain loop is used rather than fancy `any` or `IdSet` to avoid world-age issues
+            # if we want to use generated function during the early bootstrap stage when
+            # these functions are not available. (e.g., using `@generated` in `abstractarray.jl`)
+            for x in bindings
+                if x === stmt
+                    continue
+                end
+            end
+            bindings = Core.svec(bindings..., convert(Core.Binding, stmt))
         end
     end
     if !isempty(bindings)
-        ci.edges = Core.svec(bindings...)
+        ci.edges = bindings
     end
     return ci
 end