create isUnaExp(), isBinExp(), isBinAssignExp()

[WalterBright]

Use flags instead of inheritance/casting to determine these categories.

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

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Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#13656"

[WalterBright]

dscanner is complaining about:

/var/lib/buildkite-agent/builds/ci-agent-59bf1ce0-2222-401d-afec-f34be92c8925-4/dlang/dmd/dmd/src/dmd/expression.d(7086:14)[warn]: This enum may lead to unnecessary allocation at run-time. Use 'static immutable Eunary = [ ...' instead.

but backend/oper.d does the same thing. How do I disable that style check?

[WalterBright]

I found it. Never mind.

[ibuclaw]

This PR introduced a regression https://issues.dlang.org/show_bug.cgi?id=22788