i don't know a very small program that will make this happen, but for me, when i type _computedSchema, which is an instance variable at a particular breakpoint, it will autocomplete for me with exactly these 2 suggestions:
(1) _computedSchema@0x144b8438
(2) _computedSchemaFuture@0x144b8438
i hit enter and it says
"'': Error: line 2 pos 22: ')' expected
_computedSchemaFuture@0x144b8438
                     ^"

which kind of sounds like it's saying
"remember my suggestion? yeah, even i don't understand what i meant!"
on the other hand, if i type _computedSchema and hit escape and then hit enter, it admits that _computedSchema existed all along. i can also get the autocomplete to work correctly if i type this._computedSchema.

i want
(a) the repl to give me only suggestions that it will understand.
(b) the repl to give me every suggestion that it will understand.

chromium version 31.0.1650.0 (224845)
Dart VM version: 0.8.7.0_r29341 (Mon Oct 28 02:00:50 2013) on "linux_x64"