Rollup merge of #144008 - anatawa12:fix-double-negations, r=compiler-errors

Fix false positive double negations with macro invocation

This PR fixes false positive double_negations lint when macro expansion has negation and macro caller also has negations.

Fix rust-lang/rust#143980

3 files changed, 38 insertions, 0 deletions

diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 8244f0bed4c..73e68834232 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1585,6 +1585,8 @@ impl EarlyLintPass for DoubleNegations {
         if let ExprKind::Unary(UnOp::Neg, ref inner) = expr.kind
             && let ExprKind::Unary(UnOp::Neg, ref inner2) = inner.kind
             && !matches!(inner2.kind, ExprKind::Unary(UnOp::Neg, _))
+            // Don't lint if this jumps macro expansion boundary (Issue #143980)
+            && expr.span.eq_ctxt(inner.span)
         {
             cx.emit_span_lint(
                 DOUBLE_NEGATIONS,
diff --git a/tests/ui/lint/lint-double-negations-macro.rs b/tests/ui/lint/lint-double-negations-macro.rs
new file mode 100644
index 00000000000..a6583271d5a
--- /dev/null
+++ b/tests/ui/lint/lint-double-negations-macro.rs
@@ -0,0 +1,16 @@
+//@ check-pass
+macro_rules! neg {
+    ($e: expr) => {
+        -$e
+    };
+}
+macro_rules! bad_macro {
+    ($e: expr) => {
+        --$e //~ WARN use of a double negation
+    };
+}
+
+fn main() {
+    neg!(-1);
+    bad_macro!(1);
+}
diff --git a/tests/ui/lint/lint-double-negations-macro.stderr b/tests/ui/lint/lint-double-negations-macro.stderr
new file mode 100644
index 00000000000..d6ac9be48f3
--- /dev/null
+++ b/tests/ui/lint/lint-double-negations-macro.stderr
@@ -0,0 +1,20 @@
+warning: use of a double negation
+  --> $DIR/lint-double-negations-macro.rs:9:9
+   |
+LL |         --$e
+   |         ^^^^
+...
+LL |     bad_macro!(1);
+   |     ------------- in this macro invocation
+   |
+   = note: the prefix `--` could be misinterpreted as a decrement operator which exists in other languages
+   = note: use `-= 1` if you meant to decrement the value
+   = note: `#[warn(double_negations)]` on by default
+   = note: this warning originates in the macro `bad_macro` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: add parentheses for clarity
+   |
+LL |         -(-$e)
+   |          +   +
+
+warning: 1 warning emitted
+