[REPLCompletions] use less asinine version of listing module imports for completions

The test crashed on my machine, and I noticed the implementation of this
function was entirely nonsense. Fortunately, we already had a more
correct implementation of this function in the REPL docview code that we
could borrow from to fix this.

While here, also filter out macros, since those are rather strange
looking to see appearing in the results. We could alternatively use
`Base.is_valid_identifier`, since the main point here is to print
functions that are accessible in the module by identifier.

```
julia> @eval Base.MainInclude export broken

julia> broken = 2
2

julia>  ?(┌ Error: Error in the keymap
│   exception =
│    UndefVarError: `broken` not defined in `Base.MainInclude`
```

Author: vtjnash

stdlib/REPL/src/REPLCompletions.jl

@@ -729,24 +729,17 @@ function complete_methods(ex_org::Expr, context_module::Module=Main, shift::Bool
 end
 
 MAX_ANY_METHOD_COMPLETIONS::Int = 10
-function recursive_explore_names!(seen::IdSet, callee_module::Module, initial_module::Module, exploredmodules::IdSet{Module}=IdSet{Module}())
-    push!(exploredmodules, callee_module)
-    for name in names(callee_module; all=true, imported=true)
-        if !Base.isdeprecated(callee_module, name) && !startswith(string(name), '#') && isdefined(initial_module, name)
-            func = getfield(callee_module, name)
-            if !isa(func, Module)
-                funct = Core.Typeof(func)
-                push!(seen, funct)
-            elseif isa(func, Module) && func ∉ exploredmodules
-                recursive_explore_names!(seen, func, initial_module, exploredmodules)
-            end
-        end
+
+moduleusings(mod) = ccall(:jl_module_usings, Any, (Any,), mod)
+
+function accessible(mod::Module)
+    bindings = IdSet{Any}(Core.Typeof(getglobal(mod, s)) for s in names(mod; all=true, imported=true)
+                   if !Base.isdeprecated(mod, s) && !startswith(string(s), '#') && !startswith(string(s), '@') && isdefined(mod, s))
+    for used in moduleusings(mod)
+        union!(bindings, (Core.Typeof(getglobal(used, s)) for s in names(used)
+            if !Base.isdeprecated(used, s) && !startswith(string(s), '@') && isdefined(used, s)))
     end
-end
-function recursive_explore_names(callee_module::Module, initial_module::Module)
-    seen = IdSet{Any}()
-    recursive_explore_names!(seen, callee_module, initial_module)
-    seen
+    return collect(bindings)
 end
 
 function complete_any_methods(ex_org::Expr, callee_module::Module, context_module::Module, moreargs::Bool, shift::Bool)
@@ -764,7 +757,7 @@ function complete_any_methods(ex_org::Expr, callee_module::Module, context_modul
     # semicolon for the ".?(" syntax
     moreargs && push!(args_ex, Vararg{Any})
 
-    for seen_name in recursive_explore_names(callee_module, callee_module)
+    for seen_name in accessible(callee_module)
         complete_methods!(out, seen_name, args_ex, kwargs_ex, MAX_ANY_METHOD_COMPLETIONS, false)
     end