fix a bug while we're at it

ada4a · ada4a · commit b613be223dfc · 2025-09-28T11:30:47.000+02:00
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};
+use clippy_utils::source::{HasSession, snippet_with_applicability, snippet_with_context};
 use rustc_ast::ast::{Expr, ExprKind, MethodCall};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
@@ -42,27 +42,28 @@ declare_lint_pass!(DoubleParens => [DOUBLE_PARENS]);
 
 impl EarlyLintPass for DoubleParens {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
-        if expr.span.from_expansion() {
-            return;
-        }
-
         match &expr.kind {
             // ((..))
             // ^^^^^^ expr
             //  ^^^^  inner
             ExprKind::Paren(inner) if matches!(inner.kind, ExprKind::Paren(_) | ExprKind::Tup(_)) => {
                 // suggest removing the outer parens
-                let mut applicability = Applicability::MachineApplicable;
-                let sugg = snippet_with_applicability(cx.sess(), inner.span, "_", &mut applicability);
-                span_lint_and_sugg(
-                    cx,
-                    DOUBLE_PARENS,
-                    expr.span,
-                    "unnecessary parentheses",
-                    "remove them",
-                    sugg.to_string(),
-                    applicability,
-                );
+                if expr.span.eq_ctxt(inner.span) {
+                    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)
+                    // - otherwise, calling `snippet_with_applicability` on a not-from-macro span is fine
+                    let sugg = snippet_with_applicability(cx.sess(), inner.span, "_", &mut applicability);
+                    span_lint_and_sugg(
+                        cx,
+                        DOUBLE_PARENS,
+                        expr.span,
+                        "unnecessary parentheses",
+                        "remove them",
+                        sugg.to_string(),
+                        applicability,
+                    );
+                }
             },
 
             // func((n))
@@ -74,17 +75,19 @@ impl EarlyLintPass for DoubleParens {
                     && let ExprKind::Paren(inner) = &arg.kind =>
             {
                 // suggest removing the inner parens
-                let mut applicability = Applicability::MachineApplicable;
-                let sugg = snippet_with_applicability(cx.sess(), inner.span, "_", &mut applicability);
-                span_lint_and_sugg(
-                    cx,
-                    DOUBLE_PARENS,
-                    arg.span,
-                    "unnecessary parentheses",
-                    "remove them",
-                    sugg.to_string(),
-                    applicability,
-                );
+                if expr.span.eq_ctxt(arg.span) {
+                    let mut applicability = Applicability::MachineApplicable;
+                    let sugg = snippet_with_context(cx.sess(), inner.span, arg.span.ctxt(), "_", &mut applicability).0;
+                    span_lint_and_sugg(
+                        cx,
+                        DOUBLE_PARENS,
+                        arg.span,
+                        "unnecessary parentheses",
+                        "remove them",
+                        sugg.to_string(),
+                        applicability,
+                    );
+                }
             },
             _ => {},
         }
diff --git a/tests/ui/double_parens.fixed b/tests/ui/double_parens.fixed
@@ -1,5 +1,5 @@
 #![warn(clippy::double_parens)]
-#![expect(clippy::eq_op)]
+#![expect(clippy::eq_op, clippy::no_effect)]
 #![feature(custom_inner_attributes)]
 #![rustfmt::skip]
 
@@ -8,7 +8,7 @@ fn dummy_fn<T>(_: T) {}
 struct DummyStruct;
 
 impl DummyStruct {
-    fn dummy_method<T>(self, _: T) {}
+    fn dummy_method<T>(&self, _: T) {}
 }
 
 fn simple_double_parens() -> i32 {
@@ -60,4 +60,40 @@ fn inside_macro() {
     //~^ double_parens
 }
 
+fn issue9000(x: DummyStruct) {
+    macro_rules! foo {
+        () => {(100)}
+    }
+    // don't lint: the inner paren comes from the macro expansion
+    (foo!());
+    dummy_fn(foo!());
+    x.dummy_method(foo!());
+
+    macro_rules! baz {
+        ($n:literal) => {($n)}
+    }
+    // don't lint: don't get confused by the expression inside the inner paren
+    // having the same `ctxt` as the overall expression
+    // (this is a bug that happened during the development of the fix)
+    (baz!(100));
+    dummy_fn(baz!(100));
+    x.dummy_method(baz!(100));
+
+    // should lint: both parens are from inside the macro
+    macro_rules! bar {
+        () => {(100)}
+        //~^ double_parens
+    }
+    bar!();
+
+    // should lint: both parens are from outside the macro;
+    // make sure to suggest the macro unexpanded
+    (vec![1, 2]);
+    //~^ double_parens
+    dummy_fn(vec![1, 2]);
+    //~^ double_parens
+    x.dummy_method(vec![1, 2]);
+    //~^ double_parens
+}
+
 fn main() {}
diff --git a/tests/ui/double_parens.rs b/tests/ui/double_parens.rs
@@ -1,5 +1,5 @@
 #![warn(clippy::double_parens)]
-#![expect(clippy::eq_op)]
+#![expect(clippy::eq_op, clippy::no_effect)]
 #![feature(custom_inner_attributes)]
 #![rustfmt::skip]
 
@@ -8,7 +8,7 @@ fn dummy_fn<T>(_: T) {}
 struct DummyStruct;
 
 impl DummyStruct {
-    fn dummy_method<T>(self, _: T) {}
+    fn dummy_method<T>(&self, _: T) {}
 }
 
 fn simple_double_parens() -> i32 {
@@ -60,4 +60,40 @@ fn inside_macro() {
     //~^ double_parens
 }
 
+fn issue9000(x: DummyStruct) {
+    macro_rules! foo {
+        () => {(100)}
+    }
+    // don't lint: the inner paren comes from the macro expansion
+    (foo!());
+    dummy_fn(foo!());
+    x.dummy_method(foo!());
+
+    macro_rules! baz {
+        ($n:literal) => {($n)}
+    }
+    // don't lint: don't get confused by the expression inside the inner paren
+    // having the same `ctxt` as the overall expression
+    // (this is a bug that happened during the development of the fix)
+    (baz!(100));
+    dummy_fn(baz!(100));
+    x.dummy_method(baz!(100));
+
+    // should lint: both parens are from inside the macro
+    macro_rules! bar {
+        () => {((100))}
+        //~^ double_parens
+    }
+    bar!();
+
+    // should lint: both parens are from outside the macro;
+    // make sure to suggest the macro unexpanded
+    ((vec![1, 2]));
+    //~^ double_parens
+    dummy_fn((vec![1, 2]));
+    //~^ double_parens
+    x.dummy_method((vec![1, 2]));
+    //~^ double_parens
+}
+
 fn main() {}
diff --git a/tests/ui/double_parens.stderr b/tests/ui/double_parens.stderr
@@ -37,5 +37,34 @@ error: unnecessary parentheses
 LL |     assert_eq!(((1, 2)), (1, 2), "Error");
    |                ^^^^^^^^ help: remove them: `(1, 2)`
 
-error: aborting due to 6 previous errors
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:84:16
+   |
+LL |         () => {((100))}
+   |                ^^^^^^^ help: remove them: `(100)`
+...
+LL |     bar!();
+   |     ------ in this macro invocation
+   |
+   = 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
+   |
+LL |     ((vec![1, 2]));
+   |     ^^^^^^^^^^^^^^ help: remove them: `(vec![1, 2])`
+
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:93:14
+   |
+LL |     dummy_fn((vec![1, 2]));
+   |              ^^^^^^^^^^^^ help: remove them: `vec![1, 2]`
+
+error: unnecessary parentheses
+  --> tests/ui/double_parens.rs:95:20
+   |
+LL |     x.dummy_method((vec![1, 2]));
+   |                    ^^^^^^^^^^^^ help: remove them: `vec![1, 2]`
+
+error: aborting due to 10 previous errors
 
