From https://github.com/flutter/flutter/issues/15023, It's likely that prefer_const_constructors doesn't take into account implicit const creation.
Thanks for the report!
I've got this reproduced in the latest Flutter SDK (using linter 0.1.43). Looking now to see if it's been fixed by @a14n's recent work in the area...
Confirmed 馃憤 .
Using linter 0.1.43:

Using head:

I'll look at publishing a new linter in the next few days to get this fix out for integration into the Flutter SDK.
Awesome! Thanks for digging into it.
I wouldn't have bet it works. :smile:
@pq thanks for the check.
Fixed by @a14n in 0.1.44 馃帀
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Awesome! Thanks for digging into it.