Rollup merge of #47896 -...
Rollup merge of #47896 - zackmdavis:and_the_case_of_the_necessary_unnecessary_parens, r=nikomatsakis decline to lint technically-unnecessary parens in function or method arguments inside of nested macros In #46980 ("in which the unused-parens lint..." (14982db2)), the unused-parens lint was made to check function and method arguments, which it previously did not (seemingly due to oversight rather than willful design). However, in #47775 and discussion thereon, user–developers of Geal/nom and graphql-rust/juniper reported that the lint was seemingly erroneously triggering on certain complex macros in those projects. While this doesn't seem like a bug in the lint in the particular strict sense that the expanded code would, in fact, contain unncecessary parentheses, it also doesn't seem like the sort of thing macro authors should have to think about: the spirit of the unused-parens lint is to prevent needless clutter in code, not to give macro authors extra heartache in the handling of token trees. We propose the expediency of declining to lint unused parentheses in function or method args inside of nested expansions: we believe that this should eliminate the petty, troublesome lint warnings reported in the issue, without forgoing the benefits of the lint in simpler macros. It seemed like too much duplicated code for the `Call` and `MethodCall` match arms to duplicate the nested-macro check in addition to each having their own `for` loop, so this occasioned a slight refactor so that the function and method cases could share code—hopefully the overall intent is at least no less clear to the gentle reader. This is concerning #47775.
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