Rollup merge of #66983 - weiznich:bugfix/issue_66295, r=estebank

Fix `unused_parens` triggers on macro by example code

Fix #66295

Unfortunately this does also break [an existing test](https://github.com/rust-lang/rust/blob/4787e97475de6be9487e3d9255a9c2d3c0bf9252/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs#L22). I'm not sure how to handle that, because that seems to be quite similar to the allowed cases

If this gets accepted it would be great to backport this fix to beta.

5 files changed, 23 insertions, 30 deletions

diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs
index f7de7ec7e18..e6f39cca6dc 100644
--- a/src/librustc_lint/unused.rs
+++ b/src/librustc_lint/unused.rs
@@ -355,7 +355,9 @@ impl UnusedParens {
         match value.kind {
             ast::ExprKind::Paren(ref inner) => {
                 if !Self::is_expr_parens_necessary(inner, followed_by_block) &&
-                    value.attrs.is_empty() {
+                    value.attrs.is_empty() &&
+                    !value.span.from_expansion()
+                {
                     let expr_text = if let Ok(snippet) = cx.sess().source_map()
                         .span_to_snippet(value.span) {
                             snippet
diff --git a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs
index ab9baa79b8b..0a951cfa91c 100644
--- a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs
+++ b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.rs
@@ -17,10 +17,7 @@ macro_rules! the_worship_the_heart_lifts_above {
 
 macro_rules! and_the_heavens_reject_not {
     () => {
-        // ↓ But let's test that we still lint for unused parens around
-        // function args inside of simple, one-deep macros.
         #[allow(dead_code)] fn the_night_for_the_morrow() -> Option<isize> { Some((2)) }
-        //~^ WARN unnecessary parentheses around function argument
     }
 }
 
diff --git a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr b/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr
deleted file mode 100644
index 57cdcd70e9d..00000000000
--- a/src/test/ui/lint/issue-47775-nested-macro-unnecessary-parens-arg.stderr
+++ /dev/null
@@ -1,15 +0,0 @@
-warning: unnecessary parentheses around function argument
-  --> $DIR/issue-47775-nested-macro-unnecessary-parens-arg.rs:22:83
-   |
-LL |         #[allow(dead_code)] fn the_night_for_the_morrow() -> Option<isize> { Some((2)) }
-   |                                                                                   ^^^ help: remove these parentheses
-...
-LL | and_the_heavens_reject_not!();
-   | ------------------------------ in this macro invocation
-   |
-note: lint level defined here
-  --> $DIR/issue-47775-nested-macro-unnecessary-parens-arg.rs:3:9
-   |
-LL | #![warn(unused_parens)]
-   |         ^^^^^^^^^^^^^
-
diff --git a/src/test/ui/lint/lint-unnecessary-parens.rs b/src/test/ui/lint/lint-unnecessary-parens.rs
index 9f42b855a87..12ffb6d3c66 100644
--- a/src/test/ui/lint/lint-unnecessary-parens.rs
+++ b/src/test/ui/lint/lint-unnecessary-parens.rs
@@ -25,6 +25,12 @@ fn passes_unused_parens_lint() -> &'static (dyn Trait) {
     panic!()
 }
 
+macro_rules! baz {
+    ($($foo:expr),+) => {
+        ($($foo),*)
+    }
+}
+
 fn main() {
     foo();
     bar((true)); //~ ERROR unnecessary parentheses around function argument
@@ -55,4 +61,7 @@ fn main() {
     let mut _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a = (0); //~ ERROR unnecessary parentheses around assigned value
     _a += (1); //~ ERROR unnecessary parentheses around assigned value
+
+    let _a = baz!(3, 4);
+    let _b = baz!(3);
 }
diff --git a/src/test/ui/lint/lint-unnecessary-parens.stderr b/src/test/ui/lint/lint-unnecessary-parens.stderr
index adc1069b64d..541ae7aa4b5 100644
--- a/src/test/ui/lint/lint-unnecessary-parens.stderr
+++ b/src/test/ui/lint/lint-unnecessary-parens.stderr
@@ -23,25 +23,25 @@ LL | fn unused_parens_around_return_type() -> (u32) {
    |                                          ^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around function argument
-  --> $DIR/lint-unnecessary-parens.rs:30:9
+  --> $DIR/lint-unnecessary-parens.rs:36:9
    |
 LL |     bar((true));
    |         ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `if` condition
-  --> $DIR/lint-unnecessary-parens.rs:32:8
+  --> $DIR/lint-unnecessary-parens.rs:38:8
    |
 LL |     if (true) {}
    |        ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `while` condition
-  --> $DIR/lint-unnecessary-parens.rs:33:11
+  --> $DIR/lint-unnecessary-parens.rs:39:11
    |
 LL |     while (true) {}
    |           ^^^^^^ help: remove these parentheses
 
 warning: denote infinite loops with `loop { ... }`
-  --> $DIR/lint-unnecessary-parens.rs:33:5
+  --> $DIR/lint-unnecessary-parens.rs:39:5
    |
 LL |     while (true) {}
    |     ^^^^^^^^^^^^ help: use `loop`
@@ -49,43 +49,43 @@ LL |     while (true) {}
    = note: `#[warn(while_true)]` on by default
 
 error: unnecessary parentheses around `match` head expression
-  --> $DIR/lint-unnecessary-parens.rs:35:11
+  --> $DIR/lint-unnecessary-parens.rs:41:11
    |
 LL |     match (true) {
    |           ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `let` head expression
-  --> $DIR/lint-unnecessary-parens.rs:38:16
+  --> $DIR/lint-unnecessary-parens.rs:44:16
    |
 LL |     if let 1 = (1) {}
    |                ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around `let` head expression
-  --> $DIR/lint-unnecessary-parens.rs:39:19
+  --> $DIR/lint-unnecessary-parens.rs:45:19
    |
 LL |     while let 1 = (2) {}
    |                   ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around method argument
-  --> $DIR/lint-unnecessary-parens.rs:53:24
+  --> $DIR/lint-unnecessary-parens.rs:59:24
    |
 LL |     X { y: false }.foo((true));
    |                        ^^^^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:55:18
+  --> $DIR/lint-unnecessary-parens.rs:61:18
    |
 LL |     let mut _a = (0);
    |                  ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:56:10
+  --> $DIR/lint-unnecessary-parens.rs:62:10
    |
 LL |     _a = (0);
    |          ^^^ help: remove these parentheses
 
 error: unnecessary parentheses around assigned value
-  --> $DIR/lint-unnecessary-parens.rs:57:11
+  --> $DIR/lint-unnecessary-parens.rs:63:11
    |
 LL |     _a += (1);
    |           ^^^ help: remove these parentheses