Fixed parenthesis enclosed expression issue

[ericzhang6222]

Fixes #442 .

Changes proposed in this pull request:

• Will pasre (a) in let a = 5;(a) to expression.

Checklist:

• [x] Added related tests
• [x] Made corresponding changes to the documentation

[coveralls]

Pull Request Test Coverage Report for Build cda6ddda5ba37a717d072dab07907ca18b9ded5d-PR-466

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 45.967%

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Totals
Change from base Build aec765a02f3d109c8826346d5cc3f5051b7eef10:	0.0%
Covered Lines:	4172
Relevant Lines:	9076

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💛 - Coveralls