diff options
3 files changed, 83 insertions, 9 deletions
diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs index ef6475f9ee4..56f863ab3aa 100644 --- a/src/librustc_lint/unused.rs +++ b/src/librustc_lint/unused.rs @@ -302,19 +302,38 @@ impl EarlyLintPass for UnusedParens { Assign(_, ref value) => (value, "assigned value", false), AssignOp(.., ref value) => (value, "assigned value", false), InPlace(_, ref value) => (value, "emplacement value", false), - Call(_, ref args) => { - for arg in args { - self.check_unused_parens_core(cx, arg, "function argument", false) + // either function/method call, or something this lint doesn't care about + ref call_or_other => { + let args_to_check; + let call_kind; + match *call_or_other { + Call(_, ref args) => { + call_kind = "function"; + args_to_check = &args[..]; + }, + MethodCall(_, ref args) => { + call_kind = "method"; + // first "argument" is self (which sometimes needs parens) + args_to_check = &args[1..]; + } + // actual catch-all arm + _ => { return; } } - return; - }, - MethodCall(_, ref args) => { - for arg in &args[1..] { // first "argument" is self (which sometimes needs parens) - self.check_unused_parens_core(cx, arg, "method argument", false) + // Don't lint if this is a nested macro expansion: otherwise, the lint could + // trigger in situations that macro authors shouldn't have to care about, e.g., + // when a parenthesized token tree matched in one macro expansion is matched as + // an expression in another and used as a fn/method argument (Issue #47775) + if e.span.ctxt().outer().expn_info() + .map_or(false, |info| info.call_site.ctxt().outer() + .expn_info().is_some()) { + return; + } + let msg = format!("{} argument", call_kind); + for arg in args_to_check { + self.check_unused_parens_core(cx, arg, &msg, false); } return; } - _ => return, }; self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens); } diff --git a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs new file mode 100644 index 00000000000..b4e6c5074e3 --- /dev/null +++ b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs @@ -0,0 +1,40 @@ +// Copyright 2018 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// must-compile-successfully + +#![warn(unused_parens)] + +macro_rules! the_worship_the_heart_lifts_above { + ( @as_expr, $e:expr) => { $e }; + ( @generate_fn, $name:tt) => { + #[allow(dead_code)] fn the_moth_for_the_star<'a>() -> Option<&'a str> { + Some(the_worship_the_heart_lifts_above!( @as_expr, $name )) + } + }; + ( $name:ident ) => { the_worship_the_heart_lifts_above!( @generate_fn, (stringify!($name))); } + // ↑ Notably, this does 𝘯𝘰𝘵 warn: we're declining to lint unused parens in + // function/method arguments inside of nested macros because of situations + // like those reported in Issue #47775 +} + +macro_rules! and_the_heavens_reject_not { + () => { + // ↓ But let's test that we still lint for unused parens around + // function args inside of simple, one-deep macros. + #[allow(dead_code)] fn the_night_for_the_morrow() -> Option<isize> { Some((2)) } + //~^ WARN unnecessary parentheses around function argument + } +} + +the_worship_the_heart_lifts_above!(rah); +and_the_heavens_reject_not!(); + +fn main() {} diff --git a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr new file mode 100644 index 00000000000..097ec1b1c80 --- /dev/null +++ b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr @@ -0,0 +1,15 @@ +warning: unnecessary parentheses around function argument + --> $DIR/issue-47775-nested-macro-unnecessary-parens-arg.rs:32:83 + | +32 | #[allow(dead_code)] fn the_night_for_the_morrow() -> Option<isize> { Some((2)) } + | ^^^ help: remove these parentheses +... +38 | and_the_heavens_reject_not!(); + | ------------------------------ in this macro invocation + | +note: lint level defined here + --> $DIR/issue-47775-nested-macro-unnecessary-parens-arg.rs:13:9 + | +13 | #![warn(unused_parens)] + | ^^^^^^^^^^^^^ + |