add more consistency in ast

[frolovdev]

Closes #472

[coveralls]

Pull Request Test Coverage Report for Build 2491105118

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 16 of 21 (76.19%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.03%) to 89.813%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ast/mod.rs	2	4	50.0%
src/parser.rs	14	17	82.35%

Totals
Change from base Build 2488373371:	-0.03%
Covered Lines:	8764
Relevant Lines:	9758

---

💛 - Coveralls

[alamb]

Thanks @frolovdev -- looks like a nice cleanup.

cc @andygrove

[alamb]

don't we know here that negated is true? I think the code might be clearer if this were something more like

let negated = true;
self.parse_keyword(Keyword::Exists);
self.parse_exists_expr(negated)

What do you think?

[frolovdev]

Sure, I will make an update in a minute

[frolovdev]

Made an update but use placeholder (let _) because of clippy checks

[alamb]

Looks good -- thanks @frolovdev