Lint unused parentheses around method receiver

[chenyukang]

Extends the unused_parens lint to detect unnecessary parentheses around method receivers like (x).method().

Fixes #151985

[rustbot]

compiler-builtins is developed in its own repository. If possible, consider making this change to rust-lang/compiler-builtins instead.

cc @tgross35

[rustbot]

r? @jieyouxu

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[rustbot]

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  • c1b3bf0

[chenyukang]

seems better add parens for unsafe block?

[rust-log-analyzer]

The job aarch64-gnu-llvm-20-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

test [ui] tests/ui/asm/aarch64/may_unwind.rs ... ok
test [ui] tests/ui/asm/aarch64/type-check-2-2.rs ... ok
test [ui] tests/ui/asm/aarch64/type-check-2.rs ... ok
test [ui] tests/ui/asm/aarch64/type-f16.rs ... ok
test [ui] tests/ui/asm/aarch64v8r.rs#hf ... ok
test [ui] tests/ui/asm/aarch64/type-check-3.rs ... ok
test [ui] tests/ui/asm/aarch64/sym.rs ... ok
test [ui] tests/ui/asm/aarch64v8r.rs#r82 ... ok
test [ui] tests/ui/asm/arm-low-dreg.rs ... ok
test [ui] tests/ui/asm/asm-with-nested-closure.rs ... ok
test [ui] tests/ui/asm/binary_asm_labels.rs ... ignored, only executed when the architecture is x86_64
test [ui] tests/ui/asm/aarch64v8r.rs#sf ... ok
test [ui] tests/ui/asm/cfg-parse-error.rs ... ok
test [ui] tests/ui/asm/cfg.rs#reva ... ignored, only executed when the architecture is x86_64
test [ui] tests/ui/asm/cfg.rs#revb ... ignored, only executed when the architecture is x86_64
test [ui] tests/ui/asm/bad-template.rs#aarch64 ... ok
test [ui] tests/ui/asm/conditionally-sized-ptr-fail.rs ... ok
---
test [ui] tests/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#fat2 ... ok
test [ui] tests/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#fat3 ... ok
test [ui] tests/ui/extern/issue-80074.rs ... ok
test [ui] tests/ui/extern/issue-95829.rs ... ok
test [ui] tests/ui/extern/lgamma-linkage.rs ... ok
test [ui] tests/ui/extern/no-mangle-associated-fn.rs ... ok
test [ui] tests/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#thin1 ... ok
test [ui] tests/ui/extern/not-in-block.rs ... ok
test [ui] tests/ui/extern/unsized-extern-derefmove.rs ... ok
test [ui] tests/ui/feature-gates/allow-features-empty.rs ... ok
---
test [ui] tests/ui/imports/ambiguous-9.rs ... ok
test [ui] tests/ui/imports/ambiguous-import-visibility-module.rs ... ok
test [ui] tests/ui/imports/ambiguous-glob-vs-expanded-extern.rs ... ok
test [ui] tests/ui/imports/ambiguous-8.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-glob-vs-multiouter.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-globvsglob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-no-implicit-prelude.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-non-prelude-core-glob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-non-prelude-std-glob.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-pick-core.rs ... ok
test [ui] tests/ui/imports/ambiguous-panic-pick-std.rs ... ok
---

+ error[E0433]: failed to resolve: use of undeclared type `Float`
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:14
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |              ^^^^^ use of undeclared type `Float`
+    |
+ help: consider importing this struct
+    |
+ LL + use std::mem::type_info::Float;
+    |
+ 
+ error[E0433]: failed to resolve: use of undeclared type `Float`
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:45
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |                                             ^^^^^ use of undeclared type `Float`
+    |
+ help: consider importing this struct
+    |
+ LL + use std::mem::type_info::Float;
+    |
+ 
1 error: unnecessary parentheses around method receiver
2   --> $DIR/unused-parens-method-receiver-issue-151985.rs:13:5
3    |

15 LL +     x.method();
16    |
17 
- error: aborting due to 1 previous error
+ error: unnecessary parentheses around method receiver
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:13
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |             ^                   ^
+    |
+ help: remove these parentheses
+    |
+ LL -     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+ LL +     let _ = Float::MIN_POSITIVE.midpoint(-Float::MAX);
+    |
19 
+ error: aborting due to 4 previous errors
+ 
+ For more information about this error, try `rustc --explain E0433`.
---
-   --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:28:13
+ error[E0433]: failed to resolve: use of undeclared type `Float`
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:14
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |              ^^^^^ use of undeclared type `Float`
+    |
+ help: consider importing this struct
+    |
+ LL + use std::mem::type_info::Float;
+    |
+ 
+ error[E0433]: failed to resolve: use of undeclared type `Float`
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:45
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |                                             ^^^^^ use of undeclared type `Float`
+    |
+ help: consider importing this struct
+    |
+ LL + use std::mem::type_info::Float;
+    |
+ 
+ error: unnecessary parentheses around method receiver
+   --> $DIR/unused-parens-method-receiver-issue-151985.rs:28:13
+    |
+ LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+    |             ^                   ^
+    |
+ help: remove these parentheses
+    |
+ LL -     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
+ LL +     let _ = Float::MIN_POSITIVE.midpoint(-Float::MAX);
+    |
+ error: aborting due to 4 previous errors
+ 
+ For more information about this error, try `rustc --explain E0433`.

---
5 struct Thing;
6 impl Thing {
7     fn method(self) {}

13     x.method(); //~ ERROR unnecessary parentheses around method receiver
14 
15     // Necessary parens - should NOT warn
-     let _ = (1..10).sum::<i32>();           // Range expression
-     let _ = (1_i32 + 2).abs();               // Binary expression
-     let _ = (-1_i32).abs();                  // Unary expression
-     let _ = (true as i32).abs();             // Cast expression
-     let _ = (&42).clone();                   // AddrOf expression
-     let _ = (&mut 42).clone();               // AddrOf mut expression
+     let _ = (1..10).sum::<i32>(); // Range expression
+     let _ = (1_i32 + 2).abs(); // Binary expression
+     let _ = (-1_i32).abs(); // Unary expression
+     let _ = (true as i32).abs(); // Cast expression
+     let _ = (&42).clone(); // AddrOf expression
+     let _ = (&mut 42).clone(); // AddrOf mut expression
22 
23     // Block expressions - should NOT warn
-     let _ = ({ 1_i32 }).abs();               // Block expression
+     let _ = ({ 1_i32 }).abs(); // Block expression
25     let _ = (unsafe { std::mem::zeroed::<i32>() }).abs(); // Unsafe block expression
+ 
+     // lint for path with multiple segments
+     let _ = Float::MIN_POSITIVE.midpoint(-Float::MAX);
26 }
27 


The actual fixed differed from the expected fixed
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args lint/unused-parens-method-receiver-issue-151985.rs`

error: 2 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/lint/unused-parens-method-receiver-issue-151985" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error[E0433]: failed to resolve: use of undeclared type `Float`
##[error]  --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:28:14
   |
LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
   |              ^^^^^ use of undeclared type `Float`
   |
help: consider importing this struct
   |
LL + use std::mem::type_info::Float;
   |

error[E0433]: failed to resolve: use of undeclared type `Float`
##[error]  --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:28:45
   |
LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
   |                                             ^^^^^ use of undeclared type `Float`
   |
help: consider importing this struct
   |
LL + use std::mem::type_info::Float;
   |

error: unnecessary parentheses around method receiver
##[error]  --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:13:5
   |
LL |     (x).method(); //~ ERROR unnecessary parentheses around method receiver
   |     ^ ^
   |
note: the lint level is defined here
  --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:3:9
   |
LL | #![deny(unused_parens)]
   |         ^^^^^^^^^^^^^
help: remove these parentheses
   |
LL -     (x).method(); //~ ERROR unnecessary parentheses around method receiver
LL +     x.method(); //~ ERROR unnecessary parentheses around method receiver
   |

error: unnecessary parentheses around method receiver
##[error]  --> /checkout/tests/ui/lint/unused-parens-method-receiver-issue-151985.rs:28:13
   |
LL |     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
   |             ^                   ^
   |
help: remove these parentheses
   |
LL -     let _ = (Float::MIN_POSITIVE).midpoint(-Float::MAX);
LL +     let _ = Float::MIN_POSITIVE.midpoint(-Float::MAX);
   |

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0433`.