fixup! JuliaLang#52953, follow up the refactor on REPLCompletions.jl (JuliaLang#52959)

Author: aviatesk

stdlib/REPL/src/REPLCompletions.jl

@@ -1479,17 +1479,18 @@ function UndefVarError_hint(io::IO, ex::UndefVarError)
     else
         scope = undef
     end
-    if scope !== Base && !_UndefVarError_warnfor(Base, var)
+    if scope !== Base && !_UndefVarError_warnfor(io, Base, var)
         warned = false
         for m in Base.loaded_modules_order
             m === Core && continue
             m === Base && continue
             m === Main && continue
             m === scope && continue
-            warned = _UndefVarError_warnfor(m, var) || warned
+            warned |= _UndefVarError_warnfor(io, m, var)
         end
-        warned = warned || _UndefVarError_warnfor(Core, var)
-        warned = warned || _UndefVarError_warnfor(Main, var)
+        warned ||
+            _UndefVarError_warnfor(io, Core, var) ||
+            _UndefVarError_warnfor(io, Main, var)
     end
     nothing
 end

stdlib/REPL/test/repl.jl

@@ -1675,6 +1675,27 @@ fake_repl() do stdin_write, stdout_read, repl
     @test contains(txt, "Some type information was truncated. Use `show(err)` to see complete types.")
 end
 
+try # test the functionality of `UndefVarError_hint` against `Base.remove_linenums!`
+    @assert isempty(Base.Experimental._hint_handlers)
+    Base.Experimental.register_error_hint(REPL.REPLCompletions.UndefVarError_hint, UndefVarError)
+
+    # check the requirement to trigger the hint via `UndefVarError_hint`
+    @test !isdefined(Main, :remove_linenums!) && Base.ispublic(Base, :remove_linenums!)
+
+    fake_repl() do stdin_write, stdout_read, repl
+        backend = REPL.REPLBackend()
+        repltask = @async REPL.run_repl(repl; backend)
+        write(stdin_write,
+              "remove_linenums!\n\"ZZZZZ\"\n")
+        txt = readuntil(stdout_read, "ZZZZZ")
+        write(stdin_write, '\x04')
+        wait(repltask)
+        @test occursin("Hint: a global variable of this name also exists in Base.", txt)
+    end
+finally
+    empty!(Base.Experimental._hint_handlers)
+end
+
 # Hints for tab completes
 
 fake_repl() do stdin_write, stdout_read, repl