False Positive for Performance/FixedSize

[dzirtusss]

Performance/FixedSize should not be triggered for constants definitions.

---

Expected behavior

SOME_CONST = "abc".length      # this works ok
SOME_CONST = "abc".length + 1  # should also work and not trigger cop

Actual behavior

SOME_CONST = "abc".length      # this works ok
SOME_CONST = "abc".length + 1  # this triggers Performance/FixedSize

Steps to reproduce the problem

SOME_CONST = "abc".length
SOME_CONST = "abc".length + 1

RuboCop version

0.67.2 (using Parser 2.6.2.1, running on ruby 2.5.3 x86_64-darwin18)