Missing unnecessary parentheses warning in constant expressions

[leonardo-m]

#![allow(dead_code, unused_variables)]
fn main() {
    const N1: f64 = (2.0 * 2.0);
    let n2: f64 = (2.0 * 2.0);
}

It doesn't give a warning for the unnecessary parentheses for N1:

warning: unnecessary parentheses around assigned value
 --> ...\test.rs:4:19
  |
4 |     let n2: f64 = (2.0 * 2.0);
  |                   ^^^^^^^^^^^ help: remove these parentheses
  |
  = note: `#[warn(unused_parens)]` on by default

This issue has been assigned to @Tyg13 via this comment.

[csmoe]

implemented check_item for UnusedParens to check the Const item's Expr field.

[mental32]

@rustbot claim

[mental32]

I've encountered an issue I'm not quite sure how to handle :(

After getting what looks like a correct solution up with: https://github.com/mental32/rust/commit/438ade9ae57f3b5d1abb92a05cfc52a7f18eb046

I am met with the following after starting to build stage-1:

   Compiling rustc_lint v0.0.0 (/home/mental/Desktop/open_projects/rust/src/librustc_lint)
   Compiling rustc_interface v0.0.0 (/home/mental/Desktop/open_projects/rust/src/librustc_interface)
   Compiling rustc_driver v0.0.0 (/home/mental/Desktop/open_projects/rust/src/librustc_driver)
   Compiling rustc-main v0.0.0 (/home/mental/Desktop/open_projects/rust/src/rustc)
    Finished release [optimized] target(s) in 10m 43s
Installing libLLVM.so to stage 0 (x86_64-unknown-linux-gnu)
Copying stage0 rustc from stage0 (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu / x86_64-unknown-linux-gnu)
Assembling stage1 compiler (x86_64-unknown-linux-gnu)
Building stage1 std artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
   Compiling core v0.0.0 (/home/mental/Desktop/open_projects/rust/src/libcore)
error: unnecessary parentheses around const item
  --> src/libcore/../stdarch/crates/core_arch/src/x86/sse41.rs:38:35
   |
38 | pub const _MM_FROUND_FLOOR: i32 = (_MM_FROUND_RAISE_EXC | _MM_FROUND_TO_NEG_INF);
   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses
   |
   = note: `-D unused-parens` implied by `-D warnings`

error: unnecessary parentheses around const item
  --> src/libcore/../stdarch/crates/core_arch/src/x86/sse41.rs:41:34
   |
41 | pub const _MM_FROUND_CEIL: i32 = (_MM_FROUND_RAISE_EXC | _MM_FROUND_TO_POS_INF);
   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses

error: unnecessary parentheses around const item
  --> src/libcore/../stdarch/crates/core_arch/src/x86/sse41.rs:44:35
   |
44 | pub const _MM_FROUND_TRUNC: i32 = (_MM_FROUND_RAISE_EXC | _MM_FROUND_TO_ZERO);
   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses

error: unnecessary parentheses around const item
  --> src/libcore/../stdarch/crates/core_arch/src/x86/sse41.rs:48:34
   |
48 | pub const _MM_FROUND_RINT: i32 = (_MM_FROUND_RAISE_EXC | _MM_FROUND_CUR_DIRECTION);
   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses

error: unnecessary parentheses around const item
  --> src/libcore/../stdarch/crates/core_arch/src/x86/sse41.rs:51:39
   |
51 | pub const _MM_FROUND_NEARBYINT: i32 = (_MM_FROUND_NO_EXC | _MM_FROUND_CUR_DIRECTION);
   |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses

error: aborting due to 5 previous errors

error: could not compile `core`.

To learn more, run the command again with --verbose.
command did not execute successfully: "/home/mental/Desktop/open_projects/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "/home/mental/Desktop/open_projects/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "build" "-Zconfig-profile" "--target" "x86_64-unknown-linux-gnu" "-Zbinary-dep-depinfo" "-j" "2" "--release" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/home/mental/Desktop/open_projects/rust/src/libtest/Cargo.toml" "--message-format" "json-render-diagnostics"
expected success, got: exit code: 101
failed to run: /home/mental/Desktop/open_projects/rust/build/bootstrap/debug/bootstrap build
Build completed unsuccessfully in 0:13:03

Should I open a separate Issue & PR to deal with any errors generated by unused parens or is it within the scope of this issue (and PR coming soon once I write the UI tests) to deal with them?

[csmoe]

@mental32 should be fixed within this issue, and don' forget to add a testcase named issue-67942-unnecessary-paren-in-const-expr.rs into src/test/ui/issues, then ./x.py test src/test/ui --stage 1 --bless, git add the new .stderr and updated .stderr if any.

[Tyg13]

I resolved the issue with the submodule, is it alright if I claim this? It's a small patch to land.

@rustbot claim