merge 2.21,2.23,3.5 confilicts
merge 2.21,3.5 confilicts
correct 2.21 code mistakes
correct 2.21 code mistakes
fix 3.6 attributes
fix 3.7 patterns
fix 3.8 generic parameters and arguments
fix 3.10 statements
Merge branch 'develop' of https://github.com/stanzhai/the-swift-programming-language-in-chinese into develop
Merge pull request #181 from stanzhai/develop

【校对】完成首轮人工校对