rust-lang · Jarcho · Oct 31, 2025 · Oct 23, 2025
diff --git a/clippy_lints/src/double_parens.rs b/clippy_lints/src/double_parens.rs
@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::source::{HasSession, snippet_with_applicability, snippet_with_context};
+use clippy_utils::source::{HasSession, SpanRangeExt, snippet_with_applicability, snippet_with_context};
 use rustc_ast::ast::{Expr, ExprKind, MethodCall};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
@@ -47,8 +47,12 @@ impl EarlyLintPass for DoubleParens {
             // ^^^^^^ expr
             //  ^^^^  inner
             ExprKind::Paren(inner) if matches!(inner.kind, ExprKind::Paren(_) | ExprKind::Tup(_)) => {
-                // suggest removing the outer parens
-                if expr.span.eq_ctxt(inner.span) {
+                if expr.span.eq_ctxt(inner.span)
+                    && !expr.span.in_external_macro(cx.sess().source_map())
+                    && check_source(cx, inner)
+                {
+                    // suggest removing the outer parens
+
                     let mut applicability = Applicability::MachineApplicable;
                     // We don't need to use `snippet_with_context` here, because:
                     // - if `inner`'s `ctxt` is from macro, we don't lint in the first place (see the check above)
@@ -74,8 +78,12 @@ impl EarlyLintPass for DoubleParens {
                 if let [arg] = &**args
                     && let ExprKind::Paren(inner) = &arg.kind =>
             {
-                // suggest removing the inner parens
-                if expr.span.eq_ctxt(arg.span) {
+                if expr.span.eq_ctxt(arg.span)
+                    && !arg.span.in_external_macro(cx.sess().source_map())
+                    && check_source(cx, arg)
+                {
+                    // suggest removing the inner parens
+
                     let mut applicability = Applicability::MachineApplicable;
                     let sugg = snippet_with_context(cx.sess(), inner.span, arg.span.ctxt(), "_", &mut applicability).0;
                     span_lint_and_sugg(
@@ -93,3 +101,22 @@ impl EarlyLintPass for DoubleParens {
         }
     }
 }
+
+/// Check that the span does indeed look like `(  (..)  )`
+fn check_source(cx: &EarlyContext<'_>, inner: &Expr) -> bool {
+    if let Some(sfr) = inner.span.get_source_range(cx)
+        // this is the same as `SourceFileRange::as_str`, but doesn't apply the range right away, because
+        // we're interested in the source code outside it
+        && let Some(src) = sfr.sf.src.as_ref().map(|src| src.as_str())
+        && let Some((start, outer_after_inner)) = src.split_at_checked(sfr.range.end)
+        && let Some((outer_before_inner, inner)) = start.split_at_checked(sfr.range.start)
+        && outer_before_inner.trim_end().ends_with('(')
+        && inner.starts_with('(')
+        && inner.ends_with(')')
+        && outer_after_inner.trim_start().starts_with(')')
+    {
+        true
+    } else {
+        false
+    }
+}
diff --git a/tests/ui/auxiliary/macro_rules.rs b/tests/ui/auxiliary/macro_rules.rs
@@ -57,3 +57,15 @@ macro_rules! bad_transmute {
         std::mem::transmute($e)
     };
 }
+
+#[macro_export]
+#[rustfmt::skip]
+macro_rules! double_parens {
+    ($a:expr, $b:expr, $c:expr, $d:expr) => {{
+        let a = ($a);
+        let a = (());
+        let b = ((5));
+        let c = std::convert::identity((5));
+        InterruptMask((($a.union($b).union($c).union($d)).into_bits()) as u32)
+    }};
+}
diff --git a/tests/ui/auxiliary/proc_macro_derive.rs b/tests/ui/auxiliary/proc_macro_derive.rs
@@ -230,3 +230,14 @@ pub fn allow_lint_same_span_derive(input: TokenStream) -> TokenStream {
         span_help(Group::new(Delimiter::Brace, TokenStream::new()).into()),
     ])
 }
+
+#[proc_macro_derive(DoubleParens)]
+pub fn derive_double_parens(_: TokenStream) -> TokenStream {
+    quote! {
+        fn foo() {
+            let a = (());
+            let b = ((5));
+            let c = std::convert::identity((5));
+        }
+    }
+}
diff --git a/tests/ui/double_parens.fixed b/tests/ui/double_parens.fixed
@@ -1,8 +1,13 @@
+//@aux-build:proc_macros.rs
+//@aux-build:proc_macro_derive.rs
+//@aux-build:macro_rules.rs
 #![warn(clippy::double_parens)]
 #![expect(clippy::eq_op, clippy::no_effect)]
 #![feature(custom_inner_attributes)]
 #![rustfmt::skip]
 
+use proc_macros::{external, with_span};
+
 fn dummy_fn<T>(_: T) {}
 
 struct DummyStruct;
@@ -96,4 +101,64 @@ fn issue9000(x: DummyStruct) {
     //~^ double_parens
 }
 
+fn issue15892() {
+    use macro_rules::double_parens as double_parens_external;
+
+    macro_rules! double_parens{
+        ($a:expr, $b:expr, $c:expr, $d:expr) => {{
+            let a = ($a);
+            let a = ();
+            //~^ double_parens
+            let b = (5);
+            //~^ double_parens
+            let c = std::convert::identity(5);
+            //~^ double_parens
+            InterruptMask((($a.union($b).union($c).union($d)).into_bits()) as u32)
+        }};
+    }
+
+    // Don't lint: external macro
+    (external!((5)));
+    external!(((5)));
+
+    #[repr(transparent)]
+    #[derive(Clone, Copy, PartialEq, Eq)]
+    pub struct InterruptMask(u32);
+
+    impl InterruptMask {
+        pub const OE: InterruptMask = InterruptMask(1 << 10);
+        pub const BE: InterruptMask = InterruptMask(1 << 9);
+        pub const PE: InterruptMask = InterruptMask(1 << 8);
+        pub const FE: InterruptMask = InterruptMask(1 << 7);
+        // Lint: internal macro
+        pub const E: InterruptMask = double_parens!((Self::OE), Self::BE, Self::PE, Self::FE);
+        // Don't lint: external macro
+        pub const F: InterruptMask = double_parens_external!((Self::OE), Self::BE, Self::PE, Self::FE);
+        #[allow(clippy::unnecessary_cast)]
+        pub const G: InterruptMask = external!(
+            InterruptMask((((Self::OE.union(Self::BE).union(Self::PE).union(Self::FE))).into_bits()) as u32)
+        );
+        #[allow(clippy::unnecessary_cast)]
+        // Don't lint: external proc-macro
+        pub const H: InterruptMask = with_span!(span
+            InterruptMask((((Self::OE.union(Self::BE).union(Self::PE).union(Self::FE))).into_bits()) as u32)
+        );
+        pub const fn into_bits(self) -> u32 {
+            self.0
+        }
+        #[must_use]
+        pub const fn union(self, rhs: Self) -> Self {
+            InterruptMask(self.0 | rhs.0)
+        }
+    }
+}
+
+fn issue15940() {
+    use proc_macro_derive::DoubleParens;
+
+    #[derive(DoubleParens)]
+    // Don't lint: external derive macro
+    pub struct Person;
+}
+
 fn main() {}
diff --git a/tests/ui/double_parens.rs b/tests/ui/double_parens.rs
@@ -1,8 +1,13 @@
+//@aux-build:proc_macros.rs
+//@aux-build:proc_macro_derive.rs
+//@aux-build:macro_rules.rs
 #![warn(clippy::double_parens)]
 #![expect(clippy::eq_op, clippy::no_effect)]
 #![feature(custom_inner_attributes)]
 #![rustfmt::skip]
 
+use proc_macros::{external, with_span};
+
 fn dummy_fn<T>(_: T) {}
 
 struct DummyStruct;
@@ -96,4 +101,64 @@ fn issue9000(x: DummyStruct) {
     //~^ double_parens
 }
 
+fn issue15892() {
+    use macro_rules::double_parens as double_parens_external;
+
+    macro_rules! double_parens{
+        ($a:expr, $b:expr, $c:expr, $d:expr) => {{
+            let a = ($a);
+            let a = (());
+            //~^ double_parens
+            let b = ((5));
+            //~^ double_parens
+            let c = std::convert::identity((5));
+            //~^ double_parens
+            InterruptMask((($a.union($b).union($c).union($d)).into_bits()) as u32)
+        }};
+    }
+
+    // Don't lint: external macro
+    (external!((5)));
+    external!(((5)));
+
+    #[repr(transparent)]
+    #[derive(Clone, Copy, PartialEq, Eq)]
+    pub struct InterruptMask(u32);
+
+    impl InterruptMask {
+        pub const OE: InterruptMask = InterruptMask(1 << 10);
+        pub const BE: InterruptMask = InterruptMask(1 << 9);
+        pub const PE: InterruptMask = InterruptMask(1 << 8);
+        pub const FE: InterruptMask = InterruptMask(1 << 7);
+        // Lint: internal macro
+        pub const E: InterruptMask = double_parens!((Self::OE), Self::BE, Self::PE, Self::FE);
+        // Don't lint: external macro
+        pub const F: InterruptMask = double_parens_external!((Self::OE), Self::BE, Self::PE, Self::FE);
+        #[allow(clippy::unnecessary_cast)]
+        pub const G: InterruptMask = external!(
+            InterruptMask((((Self::OE.union(Self::BE).union(Self::PE).union(Self::FE))).into_bits()) as u32)
+        );
+        #[allow(clippy::unnecessary_cast)]
+        // Don't lint: external proc-macro
+        pub const H: InterruptMask = with_span!(span
+            InterruptMask((((Self::OE.union(Self::BE).union(Self::PE).union(Self::FE))).into_bits()) as u32)
+        );
+        pub const fn into_bits(self) -> u32 {
+            self.0
+        }
+        #[must_use]
+        pub const fn union(self, rhs: Self) -> Self {
+            InterruptMask(self.0 | rhs.0)
+        }
+    }
+}
+
+fn issue15940() {
+    use proc_macro_derive::DoubleParens;
+
+    #[derive(DoubleParens)]
+    // Don't lint: external derive macro
+    pub struct Person;
+}
+
 fn main() {}
diff --git a/tests/ui/double_parens.stderr b/tests/ui/double_parens.stderr
@@ -1,5 +1,5 @@
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:15:5
+  --> tests/ui/double_parens.rs:20:5
    |
 LL |     ((0))
    |     ^^^^^ help: remove them: `(0)`
@@ -8,37 +8,37 @@ LL |     ((0))
    = help: to override `-D warnings` add `#[allow(clippy::double_parens)]`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:20:14
+  --> tests/ui/double_parens.rs:25:14
    |
 LL |     dummy_fn((0));
    |              ^^^ help: remove them: `0`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:25:20
+  --> tests/ui/double_parens.rs:30:20
    |
 LL |     x.dummy_method((0));
    |                    ^^^ help: remove them: `0`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:30:5
+  --> tests/ui/double_parens.rs:35:5
    |
 LL |     ((1, 2))
    |     ^^^^^^^^ help: remove them: `(1, 2)`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:36:5
+  --> tests/ui/double_parens.rs:41:5
    |
 LL |     (())
    |     ^^^^ help: remove them: `()`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:59:16
+  --> tests/ui/double_parens.rs:64:16
    |
 LL |     assert_eq!(((1, 2)), (1, 2), "Error");
    |                ^^^^^^^^ help: remove them: `(1, 2)`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:84:16
+  --> tests/ui/double_parens.rs:89:16
    |
 LL |         () => {((100))}
    |                ^^^^^^^ help: remove them: `(100)`
@@ -49,22 +49,55 @@ LL |     bar!();
    = note: this error originates in the macro `bar` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:91:5
+  --> tests/ui/double_parens.rs:96:5
    |
 LL |     ((vec![1, 2]));
    |     ^^^^^^^^^^^^^^ help: remove them: `(vec![1, 2])`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:93:14
+  --> tests/ui/double_parens.rs:98:14
    |
 LL |     dummy_fn((vec![1, 2]));
    |              ^^^^^^^^^^^^ help: remove them: `vec![1, 2]`
 
 error: unnecessary parentheses
-  --> tests/ui/double_parens.rs:95:20
+  --> tests/ui/double_parens.rs:100:20
    |
 LL |     x.dummy_method((vec![1, 2]));
    |                    ^^^^^^^^^^^^ help: remove them: `vec![1, 2]`
 
-error: aborting due to 10 previous errors
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:110:21
+   |
+LL |             let a = (());
+   |                     ^^^^ help: remove them: `()`
+...
+LL |         pub const E: InterruptMask = double_parens!((Self::OE), Self::BE, Self::PE, Self::FE);
+   |                                      -------------------------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `double_parens` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:112:21
+   |
+LL |             let b = ((5));
+   |                     ^^^^^ help: remove them: `(5)`
+...
+LL |         pub const E: InterruptMask = double_parens!((Self::OE), Self::BE, Self::PE, Self::FE);
+   |                                      -------------------------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `double_parens` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:114:44
+   |
+LL |             let c = std::convert::identity((5));
+   |                                            ^^^ help: remove them: `5`
+...
+LL |         pub const E: InterruptMask = double_parens!((Self::OE), Self::BE, Self::PE, Self::FE);
+   |                                      -------------------------------------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `double_parens` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 13 previous errors